How memory works

Memory capacity of brain 10 times more than thought

  • New measurements have exploded the previous estimates of the human brain's memory capacity, and also help explain how neurons have such computational power when their energy use is so low.

The question of the brain's capacity usually brings up remarks that the human brain contains about 100 billion neurons. If each one has, say, 1,000 or more connections to other neurons, this produces some 100 trillion connections in which our memory can be held. These connections are between synapses, which change in strength and size when activated. These changes are a critical part of the memory code. In fact, synaptic strength is analogous to the 1s and 0s that computers use to encode information.

But, here's the thing: unlike the binary code of computers, there are more than two sizes available to synapses. On the basis of the not-very-precise tools researchers had available, they had come up with three sizes: small, medium and large. They also had calculated that the difference between the smallest and largest was a factor of 60.

Here is where the new work comes in, because new techniques have enabled researchers to now see that synapses have far more options open to them. Synapses can, it seems, vary by as little as 8%, creating a possible 26 different sizes available, which corresponds to storing 4.7 bits of information at each synapse, as opposed to one or two.

Despite the precision that this 8% speaks to, hippocampal synapses are notoriously unreliable, with signals typically activating the next neuron only 10-20% of the time. But this seeming unreliability is a feature not a bug. It means a single spike isn't going to do the job; what's needed is a stable change in synaptic strength, which comes from repeated and averaged inputs. Synapses are constantly adjusting, averaging out their success and failure rates over time.

The researchers calculate that, for the smallest synapses, about 1,500 events cause a change in their size/ability (20 minutes), while for the largest synapses, only a couple hundred signaling events (1 to 2 minutes) cause a change. In other words, every 2 to 20 minutes, your synapses are going up or down to the next size, in response to the signals they're receiving.

Based on this new information, the new estimate is that the brain can hold at least a petabyte of information, about as much as the World Wide Web currently holds. This is ten times more than previously estimated.

At the moment, only hippocampal neurons have been investigated. More work is needed to determine whether the same is true across the brain.

In the meantime, the work has given us a better notion of how memories are encoded in the brain, increased the potential capacity of the human brain, and offers a new way of thinking about information networks that may enable engineers to build better, more energy-efficient, computers.

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Birth order has no meaningful effect on personality or IQ

Because this is such a persistent myth, I thought I should briefly report on this massive study that should hopefully put an end to this myth once and for all (I wish! Myths are not so easily squashed.)

This study used data from 377,000 U.S. high school students, and, agreeing with a previous large study, found that first-borns have a one IQ point advantage over later-born siblings, but while statistically significant, this is a difference of no practical significance.

The analysis also found that first-borns tended to be more extroverted, agreeable and conscientious, and had less anxiety than later-borns, — but those differences were “infinitesimally small”, amounting to a correlation of 0.02 (the correlation between birth order and intelligence was .04).

The study controlled for potentially confounding factors, such as a family's economic status, number of children and the relative age of the siblings at the time of the analysis.

A separate analysis of children with exactly two siblings and living with two parents, enabled the finding that there are indeed specific differences between the oldest and a second child, and between second and third children. But the magnitude of the differences was again “minuscule”.

Perhaps it's not fair to say the myth is trounced. Rather, we can say that, yeah, sure, birth order makes a difference — but the difference is so small as not to be meaningful on an individual level.




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Clarity in short-term memory shows no link with IQ

December, 2010

The two measures of working memory capacity appear to be fully independent, and only one of them is related to intelligence.

The number of items a person can hold in short-term memory is strongly correlated with their IQ. But short-term memory has been recently found to vary along another dimension as well: some people remember (‘see’) the items in short-term memory more clearly and precisely than other people. This discovery has lead to the hypothesis that both of these factors should be considered when measuring working memory capacity. But do both these aspects correlate with fluid intelligence?

A new study presented 79 students with screen displays fleetingly showing either four or eight items. After a one-second blank screen, one item was returned and the subject asked whether that object had been in a particular location previously. Their ability to detect large and small changes in the items provided an estimate of how many items the individual could hold in working memory, and how clearly they remembered them. These measures were compared with individuals’ performance on standard measures of fluid intelligence.

Analysis of data found that these two measures of working memory — number and clarity —are completely independent of each other, and that it was the number factor only that correlated with intelligence.

This is not to say that clarity is unimportant! Only that it is not related to intelligence.



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How the Brain Works

See also



Older news items (pre-2010) brought over from the old website

Learning 'sculpts' the brain's connections

The ‘resting state’ of the brain is characterized by spontaneous brain activity that has not been understood. Now a new study involving 14 volunteers has found that learning a new task causes measurable changes in that activity, and the degree of change reflects how well subjects have learned to perform the task. The volunteers’ brains were scanned while they were doing nothing, during their learning of a visual task, and afterward, while they did nothing. During the task, part of the visual cortex and frontal-parietal areas involved in the control of spatial attention were particularly active. After learning the task over 5-7 days, during the ‘resting state’ each of these two regions was more likely to be active when the other region wasn't. Subjects who were more successful at the task exhibited a higher degree of this "anti-correlation".

Lewis, C. M., Baldassarre, A., Committeri, G., Romani, G. L., & Corbetta, M. (2009). Learning sculpts the spontaneous activity of the resting human brain. Proceedings of the National Academy of Sciences, 106(41), 17558-17563. doi: 10.1073/pnas.0902455106.

White matter helps brain learn

Research has concentrated on the effects of learning on gray matter, but in a new study involving 24 right-handed volunteers given 6 weeks of training in juggling, white matter was also investigated. It was found that there was not only changes in gray matter in a part of the parietal lobe associated with spatial coordination, but also the myelin in the same region appeared thicker. The gains in both were eroded after four weeks of no juggling. The findings indicate that gray matter and white matter are more interdependent than thought.

Presented at the 15th Annual Meeting of the Organization for Human Brain Mapping held in San Francisco June 18-23.

Circadian clock may be critical for remembering what you learn

We know circadian rhythm affects learning and memory in that we find it easier to learn at certain times of day than others, but now a study involving Siberian hamsters has revealed that having a functioning circadian system is in itself critical to being able to remember. The finding has implications for disorders such as Down syndrome and Alzheimer's disease. The critical factor appears to be the amount of the neurotransmitter GABA, which acts to inhibit brain activity. The circadian clock controls the daily cycle of sleep and wakefulness by inhibiting different parts of the brain by releasing GABA. It seems that if it’s not working right, if the hippocampus is overly inhibited by too much GABA, then the circuits responsible for memory storage don't function properly. The effect could be fixed by giving a GABA antagonist, which blocks GABA from binding to synapses. Recent mouse studies have also demonstrated that mice with symptoms of Down syndrome and Alzheimer's also show improved learning and memory when given the same GABA antagonist. The findings may also have implications for general age-related cognitive decline, because age brings about a degradation in the circadian system. It’s also worth noting that the hamsters' circadian systems were put out of commission by manipulating the hamsters' exposure to light, in a technique that was compared to "sending them west three time zones." The effect was independent of sleep duration.

Ruby, N.F. et al 2008. Hippocampal-dependent learning requires a functional circadian system. Proceedings of the National Academy of Sciences, 105 (40), 15593-15598.

The effect of gamma waves on cognitive and language skills in children

Gamma waves are fast, high-frequency brainwaves that spike when higher cognitive processes are engaged. Research suggests that lower levels of gamma power might hinder the brain's ability to bind thoughts together. In the first study of the "resting" gamma power in the frontal cortex in young children (16, 24 and 36 months old), it’s been revealed that those with higher language and cognitive abilities had correspondingly higher gamma power than those with poorer language and cognitive scores. Children with better attention and inhibitory control also had higher gamma power. There were no differences in gamma power based on gender or socio-economic status, but children with a family history of language impairments showed lower levels of gamma activity. The finding may enable more accurate pinpointing of a child’s development, enabling earlier, and better targeted, intervention.

Benasich, A.A. et al. 2008. Early cognitive and language skills are linked to resting frontal gamma power across the first 3 years. Behavioral Brain Research, 195 (2), 215-222.

Balance in inhibition and excitation is key to learning

A new mouse study has revealed not only the mechanism for learning deficits resulting from neurofibromatosis type 1, but also something fundamental about learning. It seems that the deficits in learning experienced by mice with an abnormal version of the Nf1 gene stem from an increased release by inhibitory neurons of the inhibitory neurotransmitter GABA. Moreover, the learning deficits can be reversed with treatments that reign GABA levels back in. The study also found show that GABA levels normally swell when mice learn, suggesting that a balance of GABA, a balance between excitatory and inhibitory signals, may be key. Changes in GABA inhibition have also recently been implicated in an animal model of Down's syndrome.

Cui, Y. et al. 2008. Neurofibromin Regulation of ERK Signaling Modulates GABA Release and Learning. Cell, 135 (3), 549-560.

Deep brain stimulation may improve memory

In a truly serendipitous and surprising development, experimental brain surgery intended to suppress an obese man's appetite using the increasingly successful technique of deep-brain stimulation, induced an intense recollection of an event from his distant past. More tests showed his ability to learn was dramatically improved when the current was switched on and his brain stimulated. Scientists are now applying the technique in the first trial of the treatment in 6 patients with Alzheimer's disease. The effect is surprising in that it involves stimulation of the hypothalamus, a critical region for metabolic regulation, but not one that has ever been associated with memory. However, the best contact was in a place close to the fornix, an arched bundle of fibres that carries signals within the limbic system, which is involved in memory and emotions and is situated next to the hypothalamus. Deep brain stimulation has been used for some time to treat Parkinson’s disease and other movement disorders.

Hamani, C. et al. 2008. Memory Enhancement Induced by Hypothalamic/Fornix Deep Brain Stimulation. Annals of Neurology, 63 (1), 119-123.

Brain's voluntary chain-of-command ruled by not 1 but 2 captains

Previous research has shown a large number of brain regions (39) that are consistently active when people prepare for a mental task. It’s been assumed that all these regions work together under the command of one single region. A new study, however, indicates that there are actually two independent networks operating. The cingulo-opercular network (including the dorsal anterior cingulate/medial superior frontal cortex, anterior insula/frontal operculum, and anterior prefrontal cortex) is linked to a "sustain" signal — it turns on at the beginning, hums away constantly during the task, then turns off at the end. In contrast, the frontoparietal network (including the dorsolateral prefrontal cortex and intraparietal sulcus) is active at the start of mental tasks and during the correction of errors. The findings may help efforts to understand the effects of brain injury and develop new strategies to treat such injuries.

Dosenbach, N.U.F. et al. 2007. Distinct brain networks for adaptive and stable task control in humans. Proceedings of the National Academy of Sciences, 104 (26), 11073-11078.

How the brain detects novelty

New research suggests that the hippocampus makes predictions of what will happen next by automatically recalling an entire sequence of events in response to a single cue, allowing us to anticipate future events and detect when things do not turn out as expected. Rather than reacting to novelty, the hippocampus seems to act as a comparison device, matching up past and present experience.

Kumaran, D. & Maguire, E.A. 2006. An unexpected sequence of events: Mismatch detection in the human hippocampus. PLoS Biol 4(12): e424. DOI: 10.1371/journal.pbio.0040424
The full text is available at

Connections between neurons act as information filters in the brain

Synapses — the connections between brain cells — have long been known to be important in information-processing, but the exact nature of their role has not been clear. Are they a crucial part of the processing itself, or simply part of the transport system? Worryingly, research has suggested that synapses drop up to 90% of all incoming signals — an unreliability difficult to reconcile with the fact that brain as a whole is very reliable. A new study has cast new light on synaptic activity. It turns out that synaptic transmission is highly temperature-dependent. Previous studies had studied isolated groups of neurons at room temperature; the present study recorded data at wormer conditions — almost body temperature. And revealed that excitatory and inhibitory synapses, previously thought to always work against each other, in fact act in concert to identify patterns carrying relevant information in an incoming signal. As a result, meaningful patterns are amplified, and stray noise is discarded. This provides the experimental confirmation needed, for the view that synapses act to filter the “noise” and makes the information processing reliable.

Klyachko,V.A. & Stevens, C.F. 2006. Excitatory and Feed-Forward Inhibitory Hippocampal Synapses Work Synergistically as an Adaptive Filter of Natural Spike Trains. PLoS Biology, 4 (7), DOI: 10.1371/journal.pbio.0040207  Full text available at:

Master planners in brain may coordinate other areas' roles in cognitive tasks

Scans of 183 subjects have identified 3 brain areas most consistently active during a variety of cognitive tasks — the dorsal anterior cingulate and the left and right frontal operculum. It’s suggested that these regions coordinate the activities of specialized regions. In a rather lovely analogy, researchers suggested that if the brain in action can be compared to a symphony, with specialized sections required to pitch in at the right time to produce the desired melody, then the regions highlighted by the new study may be likened to conductors. Until now, the function of the opercula has been a mystery; the findings also suggest a rethinking of the role of the cingulate.

Dosenbach, N.U.F. et al. 2006. A core system for the implementation of task sets. Neuron, 50(5), 799-812.

How brain cells communicate

A new finding has added to our understanding of how brain cells communicate. A protein called syndapin, previously thought to have no major role in nerve communication, has proven to be the molecule that works with a key protein called dynamin to allow the transmission of messages between nerve cells. The finding has implications for the treatment of many neurological disorders.

Anggono, V. et al. 2006. Syndapin I is the phosphorylation-regulated dynamin I partner in synaptic vesicle endocytosis. Nature Neuroscience, 9, 752 – 760.

New understanding of how neurons communicate

Although we knew that the release of neurotransmitters at the synapses of neurons causes the voltage inside the neuron to fluctuate continuously — an analog signal — it’s always been thought that the axon was impassable to those fluctuations, and thus that neurons can only communicate with each other through a digital code — that is, by sending out signals whose information is reading in the timing of the pulses. A new study now suggests that the analog signal can indeed travel along the axon, and that the digital signal passed between synapses is influenced by that analog signal. The discovery may lead to a better understanding of disorders such as epilepsy and migraine, both of which involve large changes in the voltage inside neurons.

Shu, Y., Hasenstaub, A., Duque, A., Yu, Y. & McCormick, D.A. 2006. Modulation of intracortical synaptic potentials by presynaptic somatic membrane potential. Nature, advance online publication 12 April 2006.

Rating familiarity: how we do it

Previous research has indicated that recognizing a familiar object is accompanied by a reduction in activity in the medial temporal lobe. A new imaging study has confirmed the reduced activity and demonstrated that the degree of reduction is correlated with the degree of familiarity of the object (a face in this instance). The reduction began very rapidly in the recognition process. The researchers suggested that the graded response of medial temporal structures are what allows us to assess how familiar an object is.

Gonsalves, B.D., Curran, T., Norman, K.A. & Wagner, A.D. 2005. Memory Strength and Repetition Suppression: Multimodal Imaging of Medial Temporal Cortical Contributions to Recognition. Neuron, 47, 751–761.

Single cell recognition research finds specific neurons for concepts

An intriguing study surprises cognitive researchers by showing that individual neurons in the medial temporal lobe are able to recognize specific people and objects. It’s long been thought that concepts such as these require a network of cells, and this doesn’t deny that many cells are involved. However, this new study points to the importance of a single brain cell. The study of 8 epileptic subjects found variable responses from subjects, but within subjects, individuals showed remarkably specific responses to concepts. For example, a single neuron in the left posterior hippocampus of one subject responded to all pictures of actress Jennifer Aniston, and also to Lisa Kudrow, her co-star on the TV hit "Friends", but not to pictures of Jennifer Aniston together with actor Brad Pitt, and not, or only very weakly, to other famous and non-famous faces, landmarks, animals or objects. In another patient, pictures of actress Halle Berry activated a neuron in the right anterior hippocampus, as did a caricature of the actress, images of her in the lead role of the film "Catwoman," and a letter sequence spelling her name. The results suggest an invariant, sparse and explicit code, which might be important in the transformation of complex visual percepts into long-term and more abstract memories.

Quiroga, R.Q., Reddy, L., Kreiman, G., Koch, C & Fried, I. 2005. Invariant visual representation by single neurons in the human brain. Nature, 435, 1102-1107.

Brain networks change according to cognitive task

Using a newly released method to analyze functional magnetic resonance imaging, researchers have demonstrated that the interconnections between different parts of the brain are dynamic and not static. Moreover, the brain region that performs the integration of information shifts depending on the task being performed. The study involved two language tasks, in which subjects were asked to read individual words and then make a spelling or rhyming judgment. Imaging showed that the lateral temporal cortex (LTC) was active for the rhyming task, while the intraparietal sulcus (IPS) was active for the spelling task. The inferior frontal gyrus (IFG) and the fusiform gyrus (FG) were engaged by both tasks. However, Dynamic Causal Modeling (the new method for analyzing imaging data) revealed that the network took different configurations depending on the goal of the task, with each task preferentially strengthening the influences converging on the task-specific regions (LTC for rhyming, IPS for spelling). This suggests that task specific regions serve as convergence zones that integrate information from other parts of the brain. Additionally, switching between tasks led to changes in the influence of the IFG on the task-specific regions, suggesting the IFG plays a pivotal role in making task-specific regions more or less sensitive. This is consistent with previous studies showing that the IFG is active in many different language tasks and plays a role in integrating brain regions.

Bitan, T., Booth, J.R., Choy, J., Burman, D.D., Gitelman, D.R. & Mesulam, M-M. 2005. Shifts of Effective Connectivity within a Language Network during Rhyming and Spelling. Journal of Neuroscience, 25, 5397-5403.

First real-time view of developing neurons reveals surprises

New technology and a small see-through fish called a zebra fish have enabled researchers to watch individual neurons mature. Monitoring the hundreds of neurons in the region of the brain that respond to images, the researchers expected to find that young neurons fire in response to a variety of different images, then refine their role over time so that in the adult fish the neurons only respond to images moving in a certain direction or near the left or right side of the visual field. Instead they found that the neurons fired when they sensed only one type of movement as soon as the neurons were old enough to respond to the images. However, they did take time to establish stable connections. Young neurons send out branches in all directions in the hopes that some branches will connect to other neurons and form synapses that transfer information. As the neuron matures, some of these branches form stable synapses while others recede. This trial-and-error process is what establishes the final interconnected mesh of the brain.

Niell, C.M. &Smith, S.J. 2005. Functional Imaging Reveals Rapid Development of Visual Response Properties in the Zebrafish Tectum. Neuron, 45, 941-951.

Faster neuron transmission in young males

A study of 186 male and 201 female students (aged 18-25) has found that men's brain cells can transmit nerve impulses 4% faster than women's, probably due to the faster increase of white matter in the male brain during adolescence.

Reed, T.E., Vernon, P.A. & Johnson, A.M. 2005. Confirmation of correlation between brain nerve conduction velocity and intelligence level in normal adults. Intelligence, In Press, Corrected Proof, Available online 12 September 2004,5744,12170249%255E2703,00.html

New theory challenges current view of how brain stores long-term memory

The current view of long-term memory storage is that, at the molecular level, new proteins are manufactured (a process known as translation), and these newly synthesized proteins subsequently stabilize the changes underlying the memory. Thus, every new memory results in a permanent representation in the brain. A new theory of memory storage suggests instead that there is no permanent representation. Rather, memories are copied across many different brain networks. The advantage is that it is a highly flexible system, enabling rapid retrieval even of infrequent elements.
The theory suggests that the brain stores long-term memory by rapidly changing the shape of proteins already present at those synapses activated by learning. The theory explains a number of phenomena that are not properly answered by the existing theory. The theory doesn’t disagree with the view that it is the synapse that is modified in response to learning; the disagreement concerns how that synaptic modification occurs. Current theory says it is brought about by recently synthesized proteins; the new theory suggests that learning leads to a post-synthesis (post-translational) synaptic protein modification that results in changes to the shape, activity and/or location of existing synaptic proteins. It is suggested that long-term memory storage relies on a positive-feedback rehearsal system that continually updates or fine-tunes post-translational modification of previously modified synaptic proteins, thus allowing for the continual modifications of memories.

Routtenberg, A. & Rekart, J.L. 2005. Post-translational protein modification as the substrate for long-lasting memory. Trends in Neurosciences, 28 (1), 12-19.

Memory mechanism identified

Long-term memories are stored in the brain through strengthening of the connections (synapses) between neurons. Researchers have known for many years that neurons must turn on the synthesis of new proteins for long-term memory storage and synaptic strengthening to occur, but the mechanisms by which neurons accomplish these tasks have remained elusive. Now research has identified a crucial molecular pathway that allows neurons to rapidly boost their production of new proteins. The central component of this pathway, an enzyme called "mitogen-activated protein kinase" (MAPK), effectively provides a molecular switch that triggers long-term memory storage by mobilizing the protein synthesis machinery. The research also reveals that activation of MAPK increased production production of a large number of proteins. Many researchers have thought that only a very limited number of proteins are involved in long-term memory formation.

Kelleher, R.J., Govindarajan, A., Jung, H-Y., Kang, H. & Tonegawa, S. 2004. Translational Control by MAPK Signaling in Long-Term Synaptic Plasticity and Memory. Cell, 116, 467-479.

Stages of memory clarified in sleep studies

Two new studies add to our understanding of the effects of sleep on memory. Both studies involved young adults and procedural (skill) learning, and found temporary declines in performance in particular contexts (a brief description of these studies is given here). On the basis of these studies, researchers identified three stages of memory processing: the first stage of memory — its stabilization — seems to take around six hours. During this period, the memory appears particularly vulnerable to being “lost”. The second stage of memory processing — consolidation — occurs during sleep. The third and final stage is the recall phase, when the memory is once again ready to be accessed and re-edited. (see my article on consolidation for more explanation of the processes of consolidation and re-consolidation) The surprising aspect to this is the time it appears to take for memories to initially stabilize. The studies also confirm the role of sleep in the consolidation process.

Walker, M.P., Brakefield, T., Hobson, J.A. & Stickgold, R. 2003. Dissociable stages of human memory consolidation and reconsolidation. Nature, 425, 616-620.,9865,1059138,00.html

Brain implant may restore memory

An artificial hippocampus — a programmed silicone chip — is to be linked with live tissue taken from rat brains, and then will be tested on live animals. If all goes well, it will then be tested as a way to help people who have suffered brain damage due to stroke, epilepsy or Alzheimer's disease.,3604,912940,00.html

Fear-conditioning study demonstrates long-suspected link between longterm potentiation and learning

It has long been felt that learning and memory must require physical changes in neurons that increase their responsivity to other neurons, so that they will continue to respond in the long-term even in the absence of external stimuli. Until now, however, noone has been able to actually demonstrate that this long-term potentiation occurs during learning. A new direction has proved to be more successful. Investigation of changes in the amygdala (a part of the brain associated with emotional response) after rats had been trained to fear a sound, found that postsynaptic neurons in the amygdala failed to produce any noticeable increase in electrical current, suggesting they had already been potentiated by their presynaptic partners.

Tsvetkov, E., Carlezon Jr.,W.A., Benes, F.M., Kandel, E.R. & Bolshakov, V.Y. 2002. Fear Conditioning Occludes LTP-Induced Presynaptic Enhancement of Synaptic Transmission in the Cortical Pathway to the Lateral Amygdala. Neuron, 34, 289-300.

Fruit flies might help us discover how the brain knows which brain connections to strengthen

Memory in fruit flies can be improved by boosting the level of a protein called PKM. The research may provide some answers to the burning question of how particular synapses are chosen. While it is generally agreed that memories are stored as changes in the number and strength of the connections between brain neurons (synapses), it has not been known how the particular synapses involved in a memory or learned skill are selected. It is thought that PKM may be involved in a process that 'tags' synapses during memory formation.

Drier, E.A., Tello. M.K., Cowan, M., Wu, P., Blace, N., Sacktor, T.C. & Yin, J.C.P. 2002.Memory enhancement and formation by atypical PKM activity in Drosophila melanogaster. Nature Neuroscience, 5 (4),316–324.

The clearing away of excess glutamate may be important for long-term memory

Experiments with rats have demonstrated that levels of transport molecules for glutamate – chemicals that latch on to and “sweep away” glutamate – increase significantly in the period after the onset of long-term potentiation – the process believed to underlie long-term learning. This suggests that the regulation of glutamate uptake by the transport molecules may be important for maintaining the strength of connections among the neurons. Deficiencies in glutamate transporters have been implicated in neurodegenerative diseases such as amyotrophic lateral sclerosis, or Lou Gherig’s disease.

Levenson, J., Weeber, E., Selcher, J.C., Kategaya, L.S., Sweatt, J.D. & Eskin, A. 2002. Long-term potentiation and contextual fear conditioning increase neuronal glutamate uptake. Nature Neuroscience, 5,155–161.

Identification of key brain protein for long-term memory

Using mice, scientists have identified a key brain protein involved in retaining memories, which could help explain why some things are remembered and some are not. The protein CREB (cAMP response element binding protein) apparently primes brain cells to retain long-term memories. Neurons in mice engineered to express a chimeric CREB protein were found to need a smaller first stimulus to generate a lasting increase in synaptic strength (long-term potentiation).

Barco, A., Alarcon, J.M. & Kandel, E.R. 2002. Expression of Constitutively Active CREB Protein Facilitates the Late Phase of Long-Term Potentiation by Enhancing Synaptic Capture. Cell, 108 (5), 689-703.

The neural basis for motor learning

Learning happens when a brain cell gets stimulated in a way that reduces its ability to respond to a particular brain messenger called glutamate. In the cerebellum there are very large, strangely shaped brain cells called Purkinje cells that receive more connections than other types of neurons and fire 50 times per second even when you're sleeping. These cells are involved in simple motor learning processes. A recent study provides support for an earlier study that found there are fewer receptors for glutamate on the surface of neurons during long-term synaptic depression, by demonstrating that the other three possible causes for this reduced response to glutamate do not occur.

Linden, D.J. 2001.The expression of cerebellar LTD in culture is not associated with changes in AMPA-receptor kinetics, agonist affinity, or unitary conductance. Proc. Natl. Acad. Sci. USA, 98 (24), 14066-14071.

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Older news items (pre-2010) brought over from the old website

The importance of retrieval cues

An imaging study has revealed that it is retrieval cues that trigger activity in the hippocampus, rather than, as often argued, the strength of the memory. The study involved participants learning unrelated word pairs (a process which included making up sentences with the words), then being asked whether various familiar words had been previously seen or not — the words being shown first on their own, and then with their paired cue word. Brain activity for words judged familiar on their own was compared with activity for the same items when shown with context cues. Increased hippocampal activity occurred only with cued recall. Moreover, the amount of activity was not associated with familiarity strength, and recollected items were associated with greater activity relative to highly familiar items.

Cohn, M., Moscovitch, M., Lahat, A., & McAndrews, M. P. (2009). Recollection versus strength as the primary determinant of hippocampal engagement at retrieval. Proceedings of the National Academy of Sciences, 106(52), 22451-22455.

New insights into memory without conscious awareness

An imaging study in which participants were shown a previously studied scene along with three previously studied faces and asked to identify the face that had been paired with that scene earlier has found that hippocampal activity was closely tied to participants' tendency to view the associated face, even when they failed to identify it. Activity in the lateral prefrontal cortex, an area required for decision making, was sensitive to whether or not participants had responded correctly and communication between the prefrontal cortex and the hippocampus was increased during correct, but not incorrect, trials. The findings suggest that conscious memory may depend on interactions between the hippocampus and the prefrontal cortex.

Hannula, D.E. & Ranganath, C. 2009. The Eyes Have It: Hippocampal Activity Predicts Expression of Memory in Eye Movements. Neuron, 63 (5), 592-599.

Brain activity linked to anticipation revealed

Brain scans of students listening to their favorite music CDs has revealed plenty of neural activity during the silence between songs — activity that is absent in those listening to music they had never heard in sequence before. Such anticipatory activity probably occurs whenever we expect any particular action to happen. In this case, the activity took the form of excitatory signals passing from the prefrontal cortex (where planning takes place) to the nearby premotor cortex (which is involved in preparing the body to act).

Leaver, A.M. et al. 2009. Brain Activation during Anticipation of Sound Sequences. Journal of Neuroscience, 29, 2477-2485.

How we think before we speak: Making sense of sentences

Analysis of the changes in brain activity that occurred when volunteers heard or read critical sentences as part of a longer text or placed in some other type of context, has revealed how anticipatory and contextual our comprehension is. The brain relates unfolding sentences to earlier ones astonishingly quickly (brain effects usually occur before a word is even finished being spoken), and findings indicate that it does this by trying to predict upcoming information. In addition to the words themselves, the person speaking them is a crucial component in understanding what is being said. The study found brain effects occurring very rapidly when the content of a statement being spoken did not match with the voice of the speaker (e.g. "I have a large tattoo on my back" in an upper-class accent or "I like olives" in a young child's voice). It also appears that grammar is less important than various heuristics that help you arrive at the earliest possible interpretation. Speed is more important than accuracy. “Language comprehension is opportunistic, proactive, and, above all, immediately context-dependent.”

Berkum, J.J.A. 2008. Understanding Sentences in Context: What Brain Waves Can Tell Us. Current Directions in Psychological Science, 17 (6), 376-380.

Gut feelings may actually reflect a reliable memory

Recently, there has been increased interest in the power of implicit, or unconscious, memory. In the latest study, participants were briefly shown a series of colorful kaleidoscope images and asked to memorise them. Half the time, they simultaneously heard a spoken single-digit number, which they had to keep in mind until the next trial, when they indicated whether it was odd or even. On every trial they had to listen to a new number and press a button to complete the number task. They were tested a short time after the learning period by having to recognize the images they had seen earlier, from pairs of similar kaleidoscope images. It was found that people were more accurate in selecting the old image when they had been distracted than when they had paid full attention, and were also more accurate when they claimed to be guessing than when they thought an image was familiar. During implicit recognition took place, a different pattern of brain activity was observed than that seen with conscious memory experiences, specifically, frontal-occipital negative brain potentials 200–400 ms after participants saw the old image.

Voss, J.L. & Paller, K.A 2009. An electrophysiological signature of unconscious recognition memory. Nature Neuroscience, 12, 349–355.

Searching in space is like searching your mind

A study of search modes in both spatial and abstract settings has found evidence that how we look for things, such as our car keys or umbrella, could be related to how we search for more abstract needs, such as words in memory or solutions to problems. The studies compared two search modes: exploitation, where seekers stay with a place or task until they have gotten appreciable benefit from it, and exploration, where seekers move quickly from one place or one task to another, looking for a new set of resources to exploit. In the study, participants "foraged" in a computerized world, moving around until they stumbled upon a hidden supply of resources, then deciding if and when to move on, and in which direction. The scientists tracked their movements. Two different worlds ("clumpy", with fewer but richer resources, and "diffuse", with many more, but much smaller, supplies) encouraged one mode or other. The idea was to "prime" the optimal foraging strategy for each world. The volunteers then participated in a more abstract, intellectual search task -- a computerized game akin to Scrabble. It was found that although the human brain appears capable of using exploration or exploitation search modes depending on the demands of the task, it also has a tendency through "priming" to continue searching in the same way even if in a different domain, such as when switching from a spatial to an abstract task. Moreover, people who have a tendency to use one mode more in one task have a similar tendency to use that mode more in other tasks. The findings also support the view that goal-directed cognition is an evolutionary descendant of spatial-foraging behavior.

Hills, T.T., Todd, P.M. & Goldstone, R.L. 2008. Search in External and Internal Spaces: Evidence for Generalized Cognitive Search Processes. Psychological Science, 19 (8), 802-808.

More light shed on memory retrieval

A new technique has confirmed the idea that when we retrieve memories we try to reinstate our original mindset, when we formed the memory. As you search for memories of a particular event, your brain state progressively comes to resemble the state it was in when you initially experienced the event, as one memory triggers another. They also found patterns of brain activity for specific categories, such as faces, started to emerge approximately five seconds before subjects recalled items from that category — suggesting that participants were bringing to mind the general properties of the images in order to cue for specific details. The technique also enabled researchers to predict with reasonable accuracy what items participants would successfully recall.

Polyn, S.M., Natu, V.S., Cohen, J.D. & Norman, K.A. 2005. Category-Specific Cortical Activity Precedes Retrieval During Memory Search. Science, 310 (5756), 1963–1966.

Role of hippocampus in long term memory

The role of the hippocampus in the formation of new memories has been well-documented, and we know that the hippocampus is involved in transferring immediate or short-term memories into long-term memories. However, its specific contribution to the representation of very well-learned information is not well understood. Now a study has recorded the activity of individual hippocampal neurons as monkeys retrieved information from memory, demonstrating significantly different response when the stimuli were well-learned, compared to novel stimuli. This differentiated response in the hippocampus provides strong evidence for a memory signal specific for well-learned information, and suggests a way for well-learned information to be incorporated into everyday memories.

Yanike, M., Wirth, S. & Suzuki, W.A. 2004. Representation of Well-Learned Information in the Monkey Hippocampus. Neuron, 42 (3), 477-487.

How we retrieve distant memories

We know that recent memories are stored in the hippocampus, but these memories do not remain there forever. It has been less clear how we retrieve much older memories. Now studies of mice genetically altered to be unable to recall old memories have demonstrated that a part of the cortex called the anterior cingulate is critical for this process. It is suggested that, rather than this structure being the storage site for old memories, the anterior cingulate assembles signals of an old memory from different sites in the brain. Dementia may result from a malfunction in this assembling process, leaving the memory too fragmented to make proper sense. Both ageing and certain aspects of Alzheimer's disease and other dementias are all accompanied by reduced activity in the anterior cingulate.

Frankland, P.W., Bontempi, B., Talton, L.E., Kaczmarek, L. & Silva, A.J. 2004. The Involvement of the Anterior Cingulate Cortex in Remote Contextual Fear Memory. Science, 304, 881-883.

Norepinephrine important in retrieving memories

In the first description of a molecule implicated in recalling memories as opposed to laying down new memories, researchers have found that the neurotransmitter norepinephrine is essential in retrieving certain types of memories. The studies involved mutant mice lacking norepinephrine and rats treated with drugs that block some norepinephrine receptors (beta blockers). The results run counter to currently held hypotheses that suggest that stress hormones like norepinephrine are responsible for the formation of long-term consolidation of emotional memories, instead finding that norepinephrine was critical for retrieving intermediate-term contextual and spatial memories. The research may help us better understand post-traumatic stress disorder (PTSD) and depression, both of which involve alterations in memory retrieval in different ways.

Murchison, C.F., Zhang, X-Y., Zhang, W-P., Ouyang, M., Lee, A. & Thomas, S.A. 2004. A Distinct Role for Norepinephrine in Memory Retrieval. Cell, 117 (1), 131-143.

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See also


Older news items (pre-2010) brought over from the old website

More light shed on distinction between long and short-term memory

The once clear-cut distinction between long- and short-term memory has increasingly come under fire in recent years. A new study involving patients with a specific form of epilepsy called 'temporal lobe epilepsy with bilateral hippocampal sclerosis' has now clarified the distinction. The patients, who all had severely compromised hippocampi, were asked to try and memorize photographic images depicting normal scenes. Their memory was tested and brain activity recorded after five seconds or 60 minutes. As expected, the patients could not remember the images after 60 minutes, but could distinguish seen-before images from new at five seconds. However, their memory was poor when asked to recall details about the images. Brain activity showed that short-term memory for details required the coordinated activity of a network of visual and temporal brain areas, whereas standard short-term memory drew on a different network, involving frontal and parietal regions, and independent of the hippocampus.

Cashdollar, N., Malecki, U., Rugg-Gunn, F. J., Duncan, J. S., Lavie, N., & Duzel, E. (2009). Hippocampus-dependent and -independent theta-networks of active maintenance. Proceedings of the National Academy of Sciences, 106(48), 20493-20498. doi: 10.1073/pnas.0904823106.

Why smells can be so memorable

Confirming the common experience of the strength with which certain smells can evoke emotions or memories, an imaging study has found that, when people were presented with a visual object together with one, and later with a second, set of pleasant and unpleasant odors and sounds, then presented with the same objects a week later, there was unique activation in particular brain regions in the case of their first olfactory (but not auditory) associations. This unique signature existed in the hippocampus regardless of how strong the memory was — that is, it was specific to olfactory associations. Regardless of whether they were smelled or heard, people remembered early associations more clearly when they were unpleasant.

The study appeared online on November 5 in Current Biology.

Two studies help explain the spacing effect

I talked about the spacing effect in my last newsletter. Now it seems we can point to the neurology that produces it. Not only that, but the study has found a way of modifying it, to improve learning. It’s a protein called SHP-2 phosphatase that controls the spacing effect by determining how long resting intervals between learning sessions need to last so that long-lasting memories can form. The discovery happened because more than 50% of those with a learning disorder called Noonan's disease have mutations in a gene called PTP11, which encodes the SHP-2 phosphatase protein. These mutations boost the activity levels of SHP-2 phosphatase, which, in genetically modified fruit flies, disturbs the spacing effect by increasing the interval before a new chemical signal can occur (it is the repeated formation and decay of these signals that produces memory). Accordingly, those with the mutation need longer periods between repetitions to establish long-term memory.

Pagani, M.R. et al. 2009. Spacing Effect: SHP-2 Phosphatase Regulates Resting Intervals Between Learning Trials in Long-Term Memory Induction. Cell, 139 (1), 186-198.

A study involving Aplysia (often used as a model for learning because of its simplicity and the large size of its neural connections) reveals that spaced and massed training lead to different types of memory formation. The changes at the synapses that underlie learning are controlled by the release of the neurotransmitter serotonin. Four to five spaced applications of serotonin generated long-term changes in the strength of the synapse and less activation of the enzyme Protein kinase C Apl II, leading to stronger connections between neurons. However, when the application of serotonin was continuous (as in massed learning), there was much more activation of PKC Apl II, suggesting that activation of this enzyme may block the mechanisms for generating long-term memory, while retaining mechanisms for short-term memory.

Villareal, G., Li, Q., Cai, D., Fink, A. E., Lim, T., Bougie, J. K., et al. (2009). Role of Protein Kinase C in the Induction and Maintenance of Serotonin-Dependent Enhancement of the Glutamate Response in Isolated Siphon Motor Neurons of Aplysia californica. J. Neurosci., 29(16), 5100-5107.

Smart gene helps brain cells communicate

For the second time, scientists have created a smarter rat by making their brains over-express CaMKII, a protein that acts as a promoter and signaling molecule for the NR2B subunit of the NMDA receptor. Over-expressing the gene lets brain cells communicate a fraction of a second longer. The research indicates that it plays a crucial role in initiating long-term potentiation. The NR2B subunit is more common in juvenile brains; after puberty the NR2A becomes more common. This is one reason why young people tend to learn and remember better — because the NR2B keeps communication between brain cells open maybe just a hundred milliseconds longer than the NR2A. Although this genetic modification is not something that could probably be replicated in humans, it does validate NR2B as a drug target for improving memory in healthy individuals as well as those struggling with Alzheimer's or mild dementia.

Wang, D., Cui, Z., Zeng, Q., Kuang, H., Wang, L. P., Tsien, J. Z., et al. (2009). Genetic Enhancement of Memory and Long-Term Potentiation but Not CA1 Long-Term Depression in NR2B Transgenic Rats. PLoS ONE, 4(10), e7486.
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Concepts are born in the hippocampus

Concepts are at the heart of cognition. A study showed 25 people pairs of fractal patterns that represented the night sky and asked them to forecast the weather – either rain or sun – based on the patterns. The task could be achieved by either working out the conceptual principles, or simply memorizing which patterns produced which effects. However, the next task required them to make predictions using new patterns (but based on the same principles). Success on this task was predictable from the degree of activity in the hippocampus during the first, learning, phase. In the second phase, the ventromedial prefrontal cortex, important in decision-making, was active. The results indicate that concepts are learned and stored in the hippocampus, and then passed on to the vMPFC for application.

Kumaran, D. et al. 2009. Tracking the Emergence of Conceptual Knowledge during Human Decision Making. Neuron, 63 (6), 889-901.

Why we learn more from our successes than our failures

A monkey study shows for the first time how single cells in the prefrontal cortex and basal ganglia change their responses as a result of information about what is the right action and what is the wrong one. Importantly, when a behavior was successful, cells became more finely tuned to what the animal was learning — but after a failure, there was little or no change in the brain, and no improvement in behavior. The finding points to the importance of successful actions in learning new associations.

Histed, M.H., Pasupathy, A. & Miller, E.K. 2009. Learning Substrates in the Primate Prefrontal Cortex and Striatum: Sustained Activity Related to Successful Actions. Neuron, 63 (2), 244-253.

New insight into how information is encoded in the hippocampus

Theta brain waves are known to orchestrate neuronal activity in the hippocampus, and for a long time it’s been thought that these oscillations were "in sync" across the hippocampus, timing the firing of neurons like a sort of central pacemaker. A new rat study reveals that rather than being in sync, theta oscillations actually sweep along the length of the hippocampus as traveling waves. This changes our notion of how spatial information is represented in the rat brain (and presumably has implications for our brains: theta waves are ubiquitous in mammalian brains). Rather than neurons encoding points in space, it seems that what is encoded are segments of space. This would make it easier to distinguish between representations of locations from different times. It also may have significant implications for understanding how information is transmitted from the hippocampus to other areas of the brain, since different areas of the hippocampus are connected to different areas in the brain. The fact that hippocampal activity forms a traveling wave means that these target areas receive inputs from the hippocampus in a specific sequence rather than all at once.

Lubenov, E.V. & Siapas, A.G. 2009. Hippocampal theta oscillations are travelling waves. Nature, 459, 534-539.

How the brain translates memory into action

We know that the hippocampus is crucial for place learning, especially for the rapid learning of temporary events (such as where we’ve parked the car). Now a new study reveals more about how that coding for specific places connects to behaviour. Selective lesioning in rats revealed that the critical part is in the middle part of the hippocampus, where links to visuospatial information connect links to the behavioural control necessary for returning to that place after a period of time. Rats whose brain still maintained an accurate memory of place nevertheless failed to find their way when a sufficient proportion of the intermediate hippocampus was removed. The findings emphasise that memory failures are not only, or always, about actual deficits in memory, but can also be about being able to act on it.

Bast, T. et al. 2009. From Rapid Place Learning to Behavioral Performance: A Key Role for the Intermediate Hippocampus. PLoS Biology, 7(4), e1000089.

How what we like defines what we know

How we categorize items is crucial to both how we perceive them and how well we remember them. Expertise in a subject is a well-established factor in categorization — experts create more specific categories. Because experts usually enjoy their areas of expertise, and because time spent on a subject should result in finer categorization, we would expect positive feelings towards an item to result in more specific categories. However, research has found that positive feelings usually result in more global processing. A new study has found that preference does indeed result in finer categorization and, more surprisingly, that this is independent of expertise. It seems that preference itself activates focused thinking that directly targets the preferred object, enabling more detailed perception and finer categorization.

Smallman, R. & Roese, N.J. 2008. Preference Invites Categorization. Psychological Science, 19 (12).

Encoding isn’t solely in the hippocampus

Perhaps we can improve memory in older adults with a simple memory trick. The hippocampus is a vital region for learning and memory, and indeed the association of related details to form a complete memory has been thought to occur entirely within this region. However, a new imaging study has found that when volunteers memorized pairs of words such as "motor/bear" as new compound words ("motorbear") rather than separate words, then the perirhinal cortex, rather than the hippocampus, was activated, and this activity predicted whether the volunteers would be able to successfully remember the pairs in the future.

Haskins, A.L. et al. 2008. Perirhinal Cortex Supports Encoding and Familiarity-Based Recognition of Novel Associations. Neuron, 59, 554-560.

Computer model reveals how brain represents meaning

A new computational model has been developed that can predict with 77% accuracy which areas of the brain are activated when a person thinks about a specific concrete noun.  The success of the model points to a new understanding of how our brains represent meaning. The model was constructed on the basis of the frequency with which a noun co-occurs in text (from a trillion-word text corpus) with each of 25 verbs associated with sensory-motor functions, including see, hear, listen, taste, smell, eat, push, drive and lift. These 25 verbs appear to be basic building blocks the brain uses for representing meaning. The effect of each co-occurrence on the activation of each tiny voxel in an fMRI brain scan was established, and from this data, activation patterns were drawn.

Mitchell, T.M. et al. 2008. Predicting Human Brain Activity Associated with the Meanings of Nouns. Science, 320 (5880), 1191-1195.

Novel mechanism for long-term learning identified

There has always been a paradox at the heart of learning: repetition is vital, yet at the level of individual synapses, repetitive stimulation might actually reverse early gains in synaptic strength. Now the mechanism that resolves this apparent paradox has been uncovered. N-methyl-D-aspartate (NMDA) receptors appear from studies to be required for the synaptic strengthening that occurs during learning, but these receptors undergo a sort of Jekyll-and-Hyde transition after the initial phase of learning. Instead of helping synapses get stronger, they actually begin to weaken the synapses and impair further learning. The new study reveals that while the NMDA receptor is required to begin neural strengthening, a second neurotransmitter receptor — the metabotropic glutamate (mGlu) receptor — then comes into play. Using an NMDA antagonist to block NMDA receptors after the initiation of plasticity resulted in enhanced synaptic strengthening, while blocking mGlu receptors caused strengthening to stop.

Clem, R.L., Celikel, T. & Barth, A.L. 2008. Ongoing in Vivo Experience Triggers Synaptic Metaplasticity in the Neocortex. Science, 319 (5859), 101-104.

Brain protein that's a personal trainer for your memory

A brain protein called kalirin has been shown to be critical for helping you learn and remember what you learned. When you learn something new, kalirin makes the synaptic spines on your neurons grow bigger and stronger the more you repeat the lesson. This may help explain why continued intellectual activity and learning delays cognitive decline as people grow older. "It's important to keep learning so your synapses stay healthy." Previous studies have found that kalirin levels are reduced in brains of people with diseases like Alzheimer's and schizophrenia. This latest finding suggests it may be a useful target for future drug therapy for these diseases.

Xie, Z. et al . 2007. Kalirin-7 Controls Activity-Dependent Structural and Functional Plasticity of Dendritic Spines. Neuron, 56, 640-656.

Why learning takes a while

New findings about how new connections are made between brain cells sheds light on why it sometimes takes a little while before we truly ‘get’ something. It seems that, although connections are made within minutes, it takes eight hours before these connections are mature enough to transmit information, and more hours before the connections are firmly enough established to become fully functional synapses, likely to survive. It was also found that when a new spine made contact with a site already hosting a contact, the new spine was highly likely to displace the old connection. This may mean that newly learned information might lead to a fading of older information.

Nägerl, U.V., Köstinger, G., Anderson, J.C., Martin, A.C. & Bonhoeffer, T. 2007. Protracted synaptogenesis after activity-dependent spinogenesis in hippocampal neurons. The Journal of Neuroscience, 27, 8149-8156.

How memory networks are formed

We know that memories are encoded in a network of neurons, but how do the neurons “decide” which ones to connect to? A mouse study reveals that the level of a protein called CREB is critical in this decision. The findings suggest a competitive model in which eligible neurons are selected to participate in a memory trace as a function of their relative CREB activity at the time of learning.

Han, J-H et al. 2007. Neuronal Competition and Selection During Memory Formation. Science, 316 (5823), 457-460.

Support for labeling as an aid to memory

A study involving an amnesia-inducing drug has shed light on how we form new memories. Participants in the study participants viewed words, photographs of faces and landscapes, and abstract pictures one at a time on a computer screen. Twenty minutes later, they were shown the words and images again, one at a time. Half of the images they had seen earlier, and half were new. They were then asked whether they recognized each one. For one session they were given midazolam, a drug used to relieve anxiety during surgical procedures that also causes short-term anterograde amnesia, and for one session they were given a placebo.
It was found that the participants' memory while in the placebo condition was best for words, but the worst for abstract images. Midazolam impaired the recognition of words the most, impaired memory for the photos less, and impaired recognition of abstract pictures hardly at all. The finding reinforces the idea that the ability to recollect depends on the ability to link the stimulus to a context, and that unitization increases the chances of this linking occurring. While the words were very concrete and therefore easy to link to the experimental context, the photographs were of unknown people and unknown places and thus hard to distinctively label. The abstract images were also unfamiliar and not unitized into something that could be described with a single word.

Reder, L.M. et al. 2006. Drug-Induced Amnesia Hurts Recognition, but Only for Memories That Can Be Unitized. Psychological Science, 17(7), 562-

Why motivation helps memory

An imaging study has identified the brain region involved in anticipating rewards — specific brain structures in the mesolimbic region involved in the processing of emotions — and revealed how this reward center promotes memory formation. Cues to high-reward scenes that were later remembered activated the reward areas of the mesolimbic region as well as the hippocampus. Anticipatory activation also suggests that the brain actually prepares in advance to filter incoming information rather than simply reacting to the world.

Adcock, R.A., Thangavel, A., Knutson, B., Whitfield-Gabrieli, S. & Gabrieli, J.D.E. 2006. Reward-Motivated Learning: Mesolimbic Activation Precedes Memory Formation. Neuron, 50, 507–517.

New view of hippocampus’s role in memory

Amnesiacs have overturned the established view of the hippocampus, and of the difference between long-and short-term memories. It appears the hippocampus is just as important for retrieving certain types of short-term memories as it is for long-term memories. The critical thing is not the age of the memory, but the requirement to form connections between pieces of information to create a coherent episode. The researchers suggest that, for the brain, the distinction between 'long-term' memory and 'short-term' memory are less relevant than that between ‘feature’ memory and ‘conjunction’ memory — the ability to remember specific things versus how they are related. The hippocampus may be thought of as the brain's switchboard, piecing individual bits of information together in context.

Olson, I.R., Page, K., Moore, K.S., Chatterjee, A. & Verfaellie, M. 2006. Working Memory for Conjunctions Relies on the Medial Temporal Lobe. Journal of Neuroscience, 26, 4596 – 4601.

Priming the brain for learning

A new study has revealed that how successfully you form memories depends on your frame of mind beforehand. If your brain is primed to receive information, you will have less trouble recalling it later. Moreover, researchers could predict how likely the participant was to remember a word by observing brain activity immediately prior to presentation of the word.

Otten, L.J., Quayle, A.H., Akram, S., Ditewig, T.A. &Rugg, M.D. 2006. Brain activity before an event predicts later recollection. Nature, published online ahead of print 26February2006

A single memory is processed in three separate parts of the brain

A rat study has demonstrated that a single experience is indeed processed differently in separate parts of the brain. They found that when the rats were confined in a dark compartment of a familiar box and given a mild shock, the hippocampus was involved in processing memory for context, while the anterior cingulate cortex was responsible for retaining memories involving unpleasant stimuli, and the amygdala consolidated memories more broadly and influenced the storage of both contextual and unpleasant information.

Malin, E.L. & McGaugh, J.L. 2006. Differential involvement of the hippocampus, anterior cingulate cortex, and basolateral amygdala in memory for context and footshock. Proceedings of the National Academy of Sciences, 103 (6), 1959-1963.

Resting after new learning may not be laziness

In an intriguing rat study, researchers recorded brain activity while rats ran up and down a straight 1.5-metre run. As the rats ran along the track, the nerve cells fired in a very specific sequence. But to the researchers’ surprise, when the rats were resting, the same brain cells replayed the sequence of electrical firing over and over, but in reverse and speeded up. This is similar to the replay that occurs during sleep and consolidates spatial memory, but the reverse aspect has not been seen before, and is presumed to have something to do with reinforcing the sequence. The researchers suggest this may have general implications.

Foster, D.J. & Wilson, M.A. 2006. Reverse replay of behavioural sequences in hippocampal place cells during the awake state. Nature, advance online publication; published online 12 February 2006

Protein that controls how neurons change as a result of experience

Two different research teams have identified a master protein that sheds light on one of neurobiology's biggest mysteries-how neurons change as a result of individual experiences. The protein, myocyte enhancer factor 2 (MEF2), turns on and off genes that control dendritic remodeling, that is the growth and pruning of neurons. In addition, one of the teams has identified how MEF2 switches from one program to the other, that is, from dendrite-promoting to dendrite-pruning, and the researchers have identified some of MEF2's targets. It’s suggested the MEF2 pathway could play a role in autism and other neurodevelopmental diseases, and this discovery could lead to new therapies for a host of diseases in which synapses either fail to form or run rampant.

Flavell, S.W. et al. 2006. Activity-Dependent Regulation of MEF2 Transcription Factors Suppresses Excitatory Synapse Number. Science, 311(5763), 1008-1012. Shalizi, A. et al. 2006. A Calcium-Regulated MEF2 Sumoylation Switch Controls Postsynaptic Differentiation. Science, 311(5763), 1012-1017.

Concrete evidence of the 'memory code'

I’m always talking about the “memory code”, and its existence is central to theories of memory, but now, for the first time, researchers have found concrete evidence of it. The coding system was discovered during an investigation into how the primary auditory cortex responds to different sounds. Rats were trained with various tones; it was found that the more important the tone, the greater the area of auditory cortex that became tuned to it — in other words, more neurons were involved in storing the information.

Rutkowski, R.G. & Weinberger, N.M. 2005. Encoding of learned importance of sound by magnitude of representational area in primary auditory cortex. Proceedings of the National Academy of Sciences, 102 (38), 13664-13669.

Seeing the formation of a memory

An optical imaging technique has enabled researchers to visualize changes in nerve connections. The study used genetically modified fruit flies, whose neuronal connections become fluorescent during synaptic transmission. The flies were conditioned to associate a brief puff of an odor with a shock. Using a high-powered microscope to watch the fluorescent signals in flies' brains as they learned, the researchers discovered that a specific set of neurons (projection neurons), had a greater number of active connections with other neurons after the conditioning experiment. These newly active connections appeared within 3 minutes after the experiment, suggesting that the synapses which became active after the learning took place were already formed but remained "silent" until they were needed to represent the new memory. The new synaptic activity disappeared by 7 minutes after the experiment, but the flies continued to avoid the odor they associated with the shock. The study suggests that the earliest representation of a new memory occurs by rapid changes – "like flipping a switch" – in the number of neuronal connections that respond to the odor, rather than by formation of new connections or by an increase in the number of neurons that represent an odor. The fact that the flies continued to show a learned response even after the new synaptic activity waned suggests that other memory traces found at higher levels in the brain took over to encode the memory for a longer period of time.

Yu, D., Ponomarev, A. & Davis, R.L. 2004. Altered representation of the spatial code for odors after olfactory classical conditioning: memory trace formation by synaptic recruitment. Neuron, 42 (3), 437–449.

More light shed on memory encoding

Anything we perceive contains a huge amount of sensory information. How do we decide what bits to process? New research has identified brain cells that streamline and simplify sensory information, markedly reducing the brain's workload. The study found that when monkeys were taught to remember clip art pictures, their brains reduced the level of detail by sorting the pictures into categories for recall, such as images that contained "people," "buildings," "flowers," and "animals." The categorizing cells were found in the hippocampus. As humans do, different monkeys categorized items in different ways, selecting different aspects of the same stimulus image, most likely reflecting different histories, strategies, and expectations residing within individual hippocampal networks.

Hampson, R.E., Pons, T.P., Stanford, T.R. & Deadwyler, S.A. 2004. Categorization in the monkey hippocampus: A possible mechanism for encoding information into memory. PNAS, 101, 3184-3189.

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Grey Matter

Older news items (pre-2010) brought over from the old website

Healthy older brains not significantly smaller than younger brains

A study using healthy older adults from Holland's long-term Maastricht Aging Study found that the 35 cognitively healthy people who stayed free of dementia showed no significant decline in gray matter, but the 30 people who showed substantial cognitive decline although still dementia-free showed a significant reduction in brain tissue in the hippocampus and parahippocampal areas, and in the frontal and cingulate cortices. The findings suggest that atrophy in the normal older brain may have been over-estimated in earlier studies, by not screening out people whose undetected, slowly developing brain disease was killing off cells in key areas.

[1151] Burgmans S, van Boxtel MPJ, Vuurman EFPM, Smeets F, Gronenschild EHBM, Uylings HBM, Jolles J. The prevalence of cortical gray matter atrophy may be overestimated in the healthy aging brain. Neuropsychology [Internet]. 2009 ;23(5):541 - 550. Available from:

Learning to juggle grows white matter

A study in which 24 young adults practiced juggling for half an hour a day for six weeks found that they grew more white matter in the area underlying the intraparietal sulcus. This occurred in all the jugglers, regardless of skill, suggesting it's the learning process itself that is important. Previous research has found that juggling increases grey matter. After four weeks without juggling, the new white matter remained and the amount of grey matter had even increased.

[241] Scholz J, Klein MC, Behrens TEJ, Johansen-Berg H. Training induces changes in white-matter architecture. Nat Neurosci [Internet]. 2009 ;12(11):1370 - 1371. Available from:

Tetris increases gray matter and improves brain efficiency

In a study in which 26 adolescent girls played the computer game Tetris for half an hour every day for three months, their brains compared to controls increased grey matter in Brodmann Area 6 in the left frontal lobe and BAs 22 and 38 in the left temporal lobe — areas involved in planning complex coordinated movements, and coordinating sensory information. Their brains also showed greater efficiency, but in different areas — ones associated with critical thinking, reasoning, and language, mostly in the right frontal and parietal lobes. The finding points to improved efficiency being unrelated to grey matter increases.

[600] Haier RJ, Karama S, Leyba L, Jung R. MRI assessment of cortical thickness and functional activity changes in adolescent girls following three months of practice on a visual-spatial task. BMC Research Notes [Internet]. 2009 ;2(1):174 - 174. Available from:

Neural changes produced by learning to read revealed

Understanding how our brain structures change as we learn to read is difficult because of the confounding with age and the learning of other skills. Studying adult learners is also problematic because in most educated societies adult illiteracy is typically the result of learning impairments or poor health. Now a new study involving 20 former guerrillas in Colombia who are learning to read for the first time as adults has found that these late-literates showed a number of significant brain differences compared to matched adult illiterates, including more white matter between various regions, and more grey matter in various left temporal and occipital regions important for recognizing letter shapes and translating letters into speech sounds and their meanings. Particularly important were connections between the left and right angular gyri in the parietal lobe. While this area has long been known as important for reading, its function turns out to have been misinterpreted — it now appears its main role is in anticipating what we will see. The findings will help in understanding the causes of dyslexia.

[267] Carreiras M, Seghier ML, Baquero S, Estevez A, Lozano A, Devlin JT, Price CJ. An anatomical signature for literacy. Nature [Internet]. 2009 ;461(7266):983 - 986. Available from:

Changes in gray matter induced by learning

Three months of training in three-ball cascade juggling was found to be associated with a transient and highly selective increase in gray matter in the occipito-temporal cortex. A follow-up study involving 20 adults confirmed this finding and found that the change in grey matter occurred after only 7 days of training. Neither performance nor exercise alone could explain these changes, and the increase receded when training stopped. The researchers suggest that learning a new task is more critical for the brain to change its structure than continued training of an already-learned task.

[1412] Driemeyer J, Boyke J, Gaser C, Büchel C, May A. Changes in Gray Matter Induced by Learning—Revisited. PLoS ONE [Internet]. 2008 ;3(7):e2669 - e2669. Available from:

Neural substrate of congenital amusia

Research has shown that musicians have more gray matter in certain regions of the brain involved in language and auditory processing. Now a study of tone-deaf people reveals that congenital amusia, thought to be due to a severe deficit in the processing of pitch information, is also associated with differences in gray matter distribution. Tone-deaf individuals had a thicker cortex in the right inferior frontal gyrus and right auditory cortex. This may be due to abnormal neuronal migration or atypical cell pruning during development.

Hyde, K.L. et al. 2007. Cortical Thickness in Congenital Amusia: When Less Is Better Than More. The Journal of Neuroscience, 27(47), 13028-13032.

IQ-related brain areas may differ in men and women

An imaging study of 48 men and women between 18 and 84 years old found that, although men and women performed equally on the IQ tests, the brain structures involved in intelligence appeared distinct. Compared with women, men had more than six times the amount of intelligence-related gray matter, while women had about nine times more white matter involved in intelligence than men did. Women also had a large proportion of their IQ-related brain matter (86% of white and 84% of gray) concentrated in the frontal lobes, while men had 90% of their IQ-related gray matter distributed equally between the frontal lobes and the parietal lobes, and 82% of their IQ-related white matter in the temporal lobes. The implications of all this are not clear, but it is worth noting that the volume of gray matter can increase with learning, and is thus a product of environment as well as genes. The findings also demonstrate that no single neuroanatomical structure determines general intelligence and that different types of brain designs are capable of producing equivalent intellectual performance.

[938] Haier RJ, Jung RE, Yeo RA, Head K, Alkire MT. The neuroanatomy of general intelligence: sex matters. NeuroImage [Internet]. 2005 ;25(1):320 - 327. Available from:

Chronic back pain shrinks 'thinking parts' of the brain

A new study has found chronic back pain shrinks the brain by as much as 11% — equivalent to the amount of gray matter lost in 10 to 20 years of normal aging. Loss in brain density is related to pain duration, indicating that 1.3 cubic centimeters of gray matter are lost for every year of chronic pain. The study compared 26 participants with chronic back pain for more than a year with matched normal subjects.

Apkarian, A.V., Sosa, Y., Sonty, S., Levy, R.M., Harden, R.N., Parrish, T.B. & Gitelman, D.R. 2004. Chronic Back Pain Is Associated with Decreased Prefrontal and Thalamic Gray Matter Density. Journal of Neuroscience, 24, 10410-10415.

Learning languages increases gray matter density

An imaging study of 25 Britons who did not speak a second language, 25 people who had learned another European language before the age of five and 33 bilinguals who had learned a second language between 10 and 15 years old found that the density of the gray matter in the left inferior parietal cortex of the brain was greater in bilinguals than in those without a second language. The effect was particularly noticeable in the "early" bilinguals. The findings were replicated in a study of 22 native Italian speakers who had learned English as a second language between the ages of two and 34.

Mechelli, A., Crinion, J.T., Noppeney, U., O'doherty, J., Ashburner, J., Frackowiak, R.S. & Price, C.J. 2004. Neurolinguistics: Structural plasticity in the bilingual brain. Nature, 431, 757.

Intelligence based on the volume of gray matter in certain brain regions

Confirming earlier suggestions, the most comprehensive structural brain-scan study of intelligence to date supports an association between general intelligence and the volume of gray matter tissue in certain regions of the brain. Because these regions are located throughout the brain, a single "intelligence center" is unlikely. It is likely that a person's mental strengths and weaknesses depend in large part on the individual pattern of gray matter across his or her brain. Although gray matter amounts are vital to intelligence levels, only about 6% of the brain’s gray matter appears related to IQ — intelligence seems related to an efficient use of relatively few structures. The structures that are important for intelligence are the same ones implicated in memory, attention and language. There are also age differences: in middle age, more of the frontal and parietal lobes are related to IQ; less frontal and more temporal areas are related to IQ in the younger adults. Previous research has shown the regional distribution of gray matter in humans is highly heritable. The findings also challenge the recent view that intelligence may be a reflection of more subtle characteristics of the brain, such as the speed at which nerve impulses travel in the brain, or the number of neuronal connections present. It may of course be that all of these are factors.

[715] Haier RJ, Jung RE, Yeo RA, Head K, Alkire MT. Structural brain variation and general intelligence. NeuroImage [Internet]. 2004 ;23(1):425 - 433. Available from:

Growing evidence cerebellum involved in language

An imaging study of children with selective problems in short term phonological memory and others diagnosed with specific language impairment (and matched controls) found that those with selective STPM deficits and those with SLI had less gray matter in both sides of the cerebellum compared to the children in the control groups. This supports growing evidence that the cerebellum, an area of the brain once thought to be involved only in the control of movement, also plays a role in processing speech and language.

Maturation of the human brain mapped

The progressive maturation of the human brain in childhood and adolescence has now been mapped. The initial overproduction of synapses in the gray matter that occurs after birth, is followed, for the most part just before puberty, with their systematic pruning. The mapping has confirmed that this maturation process occurs in different regions at different times, and has found that the normal gray matter loss begins first in the motor and sensory parts of the brain, and then slowly spreads downwards and forwards, to areas involved in spatial orientation, speech and language development, and attention (upper and lower parietal lobes), then to the areas involved in executive functioning, attention or motor coordination (frontal lobes), and finally to the areas that integrate these functions (temporal lobe). "The surprising thing is that the sequence in which the cortex matures appears to agree with regionally relevant milestones in cognitive development, and also reflects the evolutionary sequence in which brain regions were formed."

Imaging study confirms link between exercise and cognitive function

A number of studies have suggested a link between exercise and cognitive function in older adults, but now an imaging study shows that there are actual anatomical differences in the brains of physically fit versus less fit older adults (over 55). Specifically, they found very distinct differences in the gray and white matter in the frontal, temporal, and parietal cortexes. With aging, these tissues shrink, a reduction closely matched by declines in cognitive performance. Fitness, it appears, slows that decline. A related study, published in March, suggests that women may benefit more from exercise than men.

Colcombe, S.J., Erickson, K.I., Raz, N., Webb, A.G., Cohen, N.J., McAuley, E. & Kramer, A.F. 2003. Aerobic Fitness Reduces Brain Tissue Loss in Aging Humans. Journal of Gerontology: Series A: Biological and Medical Sciences, 58, M176-M180.

More grey matter in the auditory cortex of musicians' brains

New research augments earlier findings concerning the amount and distribution of gray matter in the brains of professional musicians. It now appears that musicians also have an increased volume of grey matter in the Broca's area, an area of the brain involved in the production of language. A critical factor appears to be the number of years devoted to musical training - at least for musicians under the age of 50. The research supports recent suggestions that musicians process music like an additional language.

Sluming, V., Barrick, T., Howard, M., Cezayirli, E., Mayes, A. & Roberts, N. 2002. Voxel-Based Morphometry Reveals Increased Gray Matter Density in Broca's Area in Male Symphony Orchestra Musicians, NeuroImage, 17(3), 1613-1622.

Significant brain differences between professional musicians trained at an early age and non-musicians

Research has revealed significant differences in the gray matter distribution between professional musicians trained at an early age and non-musicians. It is most likely that this is due to intensive musical training at an early age, although it is also possible that the musicians were born with these differences, which led them to pursue musical training.

Schlaug, G. & Christian, G. Paper presented May 7 at the American Academy of Neurology's 53rd Annual Meeting in Philadelphia, PA.

Calculation difficulties in children of very low birthweight

Learning difficulties, including problems with numeracy, are common in Western populations. Many children with learning difficulty are survivors of preterm birth. Although some of these children have neurological disabilities, many are neurologically normal. A neuroimaging study of neurologically normal adolescent children who had been born preterm at 30 weeks gestation or less found an area in the left parietal lobe where children without a deficit in calculation ability have more grey matter than those who do have this deficit.

Isaacs, E.B., Edmonds, C.J., Lucas, A. & Gadian, D.G. (2001). Calculation difficulties in children of very low birthweight: A neural correlate. Brain, 124 (9, 1701-1707.

Gray matter may decline from adolescence, but white matter keeps growing until our late forties

Brain scans of 70 men, ages 19 to 76 confirms that the brain's gray matter, the cell bodies of nerve cells, declines steadily from adolescence. But surprisingly, the white matter, the fatty material that insulates the long extending branches of the nerve cells and makes nerve signals move faster, in the frontal parts of the brain appears to grow at least until the late 40's, before beginning to decline. The growth of white matter may improve the brain's ability to process information.

Bartzokis, G., Beckson, M., Lu, P.H., Nuechterlein, K.H., Edwards, N. & Mintz, J. 2001. Age-Related Changes in Frontal and Temporal Lobe Volumes in Men: A Magnetic Resonance Imaging Study. Archives of General Psychiatry, 58, 461-465.

Mental faculties unchanged until the mid-40s

A large-scale study of mental abilities in adults found that mental faculties were unchanged until the mid-40s, when a marked decline began and continued at a constant rate. The ability to remember words after a delay was especially affected. Accuracy did not seem to be affected, only speed.

The paper was presented to a British Psychological Society conference in London.,4273,4108165,00.html

Working Memory

Older news items (pre-2010) brought over from the old website

More light shed on distinction between long and short-term memory

The once clear-cut distinction between long- and short-term memory has increasingly come under fire in recent years. A new study involving patients with a specific form of epilepsy called 'temporal lobe epilepsy with bilateral hippocampal sclerosis' has now clarified the distinction. The patients, who all had severely compromised hippocampi, were asked to try and memorize photographic images depicting normal scenes. Their memory was tested and brain activity recorded after five seconds or 60 minutes. As expected, the patients could not remember the images after 60 minutes, but could distinguish seen-before images from new at five seconds. However, their memory was poor when asked to recall details about the images. Brain activity showed that short-term memory for details required the coordinated activity of a network of visual and temporal brain areas, whereas standard short-term memory drew on a different network, involving frontal and parietal regions, and independent of the hippocampus.

[996] Cashdollar N, Malecki U, Rugg-Gunn FJ, Duncan JS, Lavie N, Duzel E. Hippocampus-dependent and -independent theta-networks of active maintenance. Proceedings of the National Academy of Sciences [Internet]. 2009 ;106(48):20493 - 20498. Available from:

Short stressful events may improve working memory

We know that chronic stress has a detrimental effect on learning and memory, but a new rat study shows how acute stress (a short, sharp event) can produce a beneficial effect. The rats, trained to a level of 60-70% accuracy on a maze, were put through a 20-minute forced swim before being run through the maze again. Those who experienced this stressful event were better at running the maze 4 hours later, and a day later, than those not forced through the stressful event. It appears that the stress hormone corticosterone (cortisol in humans) increases transmission of the neurotransmitter glutamate in the prefrontal cortex and improves working memory. It also appears that chronic stress suppresses the transmission of glutamate in the prefrontal cortex of male rodents, while estrogen receptors in female rodents make them more resilient to chronic stress than male rats.

[1157] Yuen EY, Liu W, Karatsoreos IN, Feng J, McEwen BS, Yan Z. Acute stress enhances glutamatergic transmission in prefrontal cortex and facilitates working memory. Proceedings of the National Academy of Sciences of the United States of America [Internet]. 2009 ;106(33):14075 - 14079. Available from:

Individual differences in working memory capacity depend on two factors

A new computer model adds to our understanding of working memory, by showing that working memory can be increased by the action of the prefrontal cortex in reinforcing activity in the parietal cortex (where the information is temporarily stored). The idea is that the prefrontal cortex sends out a brief stimulus to the parietal cortex that generates a reverberating activation in a small subpopulation of neurons, while inhibitory interactions with neurons further away prevents activation of the entire network. This lateral inhibition is also responsible for limiting the mnemonic capacity of the parietal network (i.e. provides the limit on your working memory capacity). The model has received confirmatory evidence from an imaging study involving 25 volunteers. It was found that individual differences in performance on a short-term visual memory task were correlated with the degree to which the dorsolateral prefrontal cortex was activated and its interconnection with the parietal cortex. In other words, your working memory capacity is determined by both storage capacity (in the posterior parietal cortex) and prefrontal top-down control. The findings may help in the development of ways to improve working memory capacity, particularly when working memory is damaged.

[441] Edin F, Klingberg T, Johansson P, McNab F, Tegner J, Compte A. Mechanism for top-down control of working memory capacity. Proceedings of the National Academy of Sciences [Internet]. 2009 ;106(16):6802 - 6807. Available from:

Some short-term memories die suddenly, no fading

We don’t remember everything; the idea of memory as being a video faithfully recording every aspect of everything we have ever experienced is a myth. Every day we look at the world and hold a lot of what we say for no more than a few seconds before discarding it as not needed any more. Until now it was thought that these fleeting visual memories faded away, gradually becoming more imprecise. Now it seems that such memories remain quite accurate as long as they exist (about 4 seconds), and then just vanish away instantly. The study involved testing memory for shapes and colors in 12 adults, and it was found that the memory for shape or color was either there or not there – the answers either correct or random guesses. The probability of remembering correctly decreased between 4 and 10 seconds.

[941] Zhang W, Luck SJ. Sudden death and gradual decay in visual working memory. Psychological Science: A Journal of the American Psychological Society / APS [Internet]. 2009 ;20(4):423 - 428. Available from:

Where visual short-term memory occurs

Working memory used to be thought of as a separate ‘store’, and now tends to be regarded more as a process, a state of mind. Such a conception suggests that it may occur in the same regions of the brain as long-term memory, but in a pattern of activity that is somehow different from LTM. However, there has been little evidence for that so far. Now a new study has found that information in WM may indeed be stored via sustained, but low, activity in sensory areas. The study involved volunteers being shown an image for one second and instructed to remember either the color or the orientation of the image. After then looking at a blank screen for 10 seconds, they were shown another image and asked whether it was the identical color/orientation as the first image. Brain activity in the primary visual cortex was scanned during the 10 second delay, revealing that areas normally involved in processing color and orientation were active during that time, and that the pattern only contained the targeted information (color or orientation).

[1032] Serences JT, Ester EF, Vogel EK, Awh E. Stimulus-Specific Delay Activity in Human Primary Visual Cortex. Psychological Science [Internet]. 2009 ;20(2):207 - 214. Available from:

The finding is consistent with that of another study published this month, in which participants were shown two examples of simple striped patterns at different orientations and told to hold either one or the other of the orientations in their mind while being scanned. Orientation is one of the first and most basic pieces of visual information coded and processed by the brain. Using a new decoding technique, researchers were able to predict with 80% accuracy which of the two orientations was being remembered 11 seconds after seeing a stimulus, from the activity patterns in the visual areas. This was true even when the overall level of activity in these visual areas was very weak, no different than looking at a blank screen.

[652] Harrison SA, Tong F. Decoding reveals the contents of visual working memory in early visual areas. Nature [Internet]. 2009 ;458(7238):632 - 635. Available from:

Even toddlers can ‘chunk' information for better remembering

We all know it’s easier to remember a long number (say a phone number) when it’s broken into chunks. Now a study has found that we don’t need to be taught this; it appears to come naturally to us. The study showed 14 months old children could track only three hidden objects at once, in the absence of any grouping cues, demonstrating the standard limit of working memory. However, with categorical or spatial cues, the children could remember more. For example, when four toys consisted of two groups of two familiar objects, cats and cars, or when six identical orange balls were grouped in three groups of two.

Feigenson, L. & Halberda, J. 2008. Conceptual knowledge increases infants' memory capacity. Proceedings of the National Academy of Sciences, 105 (29), 9926-9930.

Full text available at

Brain-training to improve working memory boosts fluid intelligence

General intelligence is often separated into "fluid" and "crystalline" components, of which fluid intelligence is considered more reflective of “pure” intelligence, and largely resistant to training and learning effects. However, in a new study in which participants were given a series of training exercises designed to improve their working memory, fluid intelligence was found to have significantly improved, with the amount of improvement increasing with time spent training. The small study contradicts decades of research showing that improving on one kind of cognitive task does not improve performance on other kinds, so has been regarded with some skepticism by other researchers. More research is definitely needed, but the memory task did differ from previous studies, engaging executive functions such as those that inhibit irrelevant items, monitor performance, manage two tasks simultaneously, and update memory.

Jaeggi, S.M., Buschkuehl, M., Jonides, J. & Perrig, W.J. 2008. Improving fluid intelligence with training on working memory. PNAS, 105 (19), 6829-6833.

Working memory has a fixed number of 'slots'

A study that showed volunteers a pattern of colored squares for a tenth of a second, and then asked them to recall the color of one of the squares by clicking on a color wheel, has found that working memory acts like a high-resolution camera, retaining three or four features in high detail. Unlike a digital camera, however, it appears that you can’t increase the number of images you can store by lowering the resolution. The resolution appears to be constant for a given individual. However, individuals do differ in the resolution of each feature and the number of features that can be stored.

[278] Zhang W, Luck SJ. Discrete fixed-resolution representations in visual working memory. Nature [Internet]. 2008 ;453(7192):233 - 235. Available from:

And another study of working memory has attempted to overcome the difficulties involved in measuring a person’s working memory capacity (ensuring that no ‘chunking’ of information takes place), and concluded that people do indeed have a fixed number of ‘slots’ in their working memory. In the study, participants were shown two, five or eight small, scattered, different-colored squares in an array, which was then replaced by an array of the same squares without the colors, after which the participant was shown a single color in one location and asked to indicate whether the color in that spot had changed from the original array.

[437] Rouder JN, Morey RD, Cowan N, Zwilling CE, Morey CC, Pratte MS. An assessment of fixed-capacity models of visual working memory. Proceedings of the National Academy of Sciences [Internet]. 2008 ;105(16):5975 - 5979. Available from:

Impressive feats in visual memory

In light of all the recent experiments emphasizing how small our short-term visual memory is, it’s comforting to be reminded that, nevertheless, we have an amazing memory for pictures — in the right circumstances. Those circumstances include looking at images of familiar objects, as opposed to abstract artworks, and being motivated to do well (the best-scoring participant was given a cash prize). In the study, 14 people aged 18 to 40 viewed 2,500 images, one at a time, for a few seconds. Afterwards, they were shown pairs of images and asked to select the exact image they had seen earlier. The previously viewed item could be paired with either an object from a novel category, an object of the same basic-level category, or the same object in a different state or pose. Stunningly, participants on average chose the correct image 92%, 88% and 87% of the time, in each of the three pairing categories respectively.

[870] Brady TF, Konkle T, Alvarez GA, Oliva A. Visual long-term memory has a massive storage capacity for object details. Proceedings of the National Academy of Sciences [Internet]. 2008 ;105(38):14325 - 14329. Available from:

Full text available at

Children's under-achievement could be down to poor working memory

A survey of over three thousand children has found that 10% of school children across all age ranges suffer from poor working memory seriously affecting their learning. However, poor working memory is rarely identified by teachers, who often describe children with this problem as inattentive or as having lower levels of intelligence. The researchers have developed a new tool, a combination of a checklist and computer programme called the Working Memory Rating Scale, that enables teachers to identify and assess children's memory capacity in the classroom from as early as four years old. The tool has already been piloted successfully in 35 schools across the UK, and is now widely available. It has been translated into ten foreign languages.

More on how short-term memory works

It’s been established that visual working memory is severely limited — that, on average, we can only be aware of about four objects at one time. A new study explored the idea that this capacity might be affected by complexity, that is, that we can think about fewer complex objects than simple objects. It found that complexity did not affect memory capacity. It also found that some people have clearer memories of the objects than other people, and that this is not related to how many items they can remember. That is, a high IQ is associated with the ability to hold more items in working memory, but not with the clarity of those items.

[426] Awh E, Barton B, Vogel EK. Visual working memory represents a fixed number of items regardless of complexity. Psychological Science: A Journal of the American Psychological Society / APS [Internet]. 2007 ;18(7):622 - 628. Available from:

Executive function as important as IQ for math success

A study of 141 preschoolers from low-income homes has found that a child whose IQ and executive functioning were both above average was three times more likely to succeed in math than a child who simply had a high IQ. The parts of executive function that appear to be particularly linked to math ability in preschoolers are working memory and inhibitory control. In this context, working memory may be thought of as the ability to keep information or rules in mind while performing mental tasks. Inhibitory control is the ability to halt automatic impulses and focus on the problem at hand. Inhibitory control was also important for reading ability. The finding offers the hope that training to improve executive function will improve academic performance

Blair, C. & Razza, R.P. 2007. Relating Effortful Control, Executive Function, and False Belief Understanding to Emerging Math and Literacy Ability in Kindergarten. Child Development, 78 (2), 647–663.

New research shows why too much memory may be a bad thing

People who are able to easily and accurately recall historical dates or long-ago events may have a harder time with word recall or remembering the day's current events. A mouse study reveals why. Neurogenesis has been thought of as a wholly good thing — having more neurons is surely a good thing — but now a mouse study has found that stopping neurogenesis in the hippocampus improved working memory. Working memory is highly sensitive to interference from information previously stored in memory, so it may be that having too much information may hinder performing everyday working memory tasks.

Saxe, M.D. et al. 2007. Paradoxical influence of hippocampal neurogenesis on working memory. Proceedings of the National Academy of Sciences, 104 (11), 4642-4646.

Implicit stereotypes and gender identification may affect female math performance

Relatedly, another study has come out showing that women enrolled in an introductory calculus course who possessed strong implicit gender stereotypes, (for example, automatically associating "male" more than "female" with math ability and math professions) and were likely to identify themselves as feminine, performed worse relative to their female counterparts who did not possess such stereotypes and who were less likely to identify with traditionally female characteristics. Strikingly, a majority of the women participating in the study explicitly expressed disagreement with the idea that men have superior math ability, suggesting that even when consciously disavowing stereotypes, female math students are still susceptible to negative perceptions of their ability.

Kiefer, A.K., & Sekaquaptewa, D. 2007. Implicit stereotypes, gender identification, and math performance: a prospective study of female math students. Psychological Science, 18(1), 13-18.

Reducing the racial achievement gap

And staying with the same theme, a study that came out six months ago, and recently reviewed on the excellent new Scientific American Mind Matters blog, revealed that a single, 15-minute intervention erased almost half the racial achievement gap between African American and white students. The intervention involved writing a brief paragraph about which value, from a list of values, was most important to them and why. The intervention improved subsequent academic performance for some 70% of the African American students, but none of the Caucasians. The study was repeated the following year with the same results. It is thought that the effect of the intervention was to protect against the negative stereotypes regarding the intelligence and academic capabilities of African Americans.

[1082] Cohen GL, Garcia J, Apfel N, Master A. Reducing the Racial Achievement Gap: A Social-Psychological Intervention. Science [Internet]. 2006 ;313(5791):1307 - 1310. Available from:

Highly accomplished people more prone to failure than others when under stress

One important difference between those who do well academically and those who don’t is often working memory capacity. Those with a high working memory capacity find it easier to read and understand and reason, than those with a smaller capacity. However, a new study suggests there is a downside. Such people tend to heavily rely on their abundant supply of working memory and are therefore disadvantaged when challenged to solve difficult problems, such as mathematical ones, under pressure — because the distraction caused by stress consumes their working memory. They then fall back on the less accurate short-cuts that people with less adequate supplies of working memory tend to use, such as guessing and estimation. Such methods are not made any worse by working under pressure. In the study involving 100 undergraduates, performance of students with strong working memory declined to the same level as those with more limited working memory, when the students were put under pressure. Those with more limited working memory performed as well under added pressure as they did without the stress.

The findings were presented February 17 at the annual meeting of the American Association for the Advancement of Science.

Common gene version optimizes thinking but carries a risk

On the same subject, another study has found that the most common version of DARPP-32, a gene that shapes and controls a circuit between the striatum and prefrontal cortex, optimizes information filtering by the prefrontal cortex, thus improving working memory capacity and executive control (and thus, intelligence). However, the same version was also more prevalent among people who developed schizophrenia, suggesting that a beneficial gene variant may translate into a disadvantage if the prefrontal cortex is impaired. In other words, one of the things that make humans more intelligent as a species may also make us more vulnerable to schizophrenia.

[864] Kolachana B, Kleinman JE, Weinberger DR, Meyer-Lindenberg A, Straub RE, Lipska BK, Verchinski BA, Goldberg T, Callicott JH, Egan MF, et al. Genetic evidence implicating DARPP-32 in human frontostriatal structure, function, and cognition. Journal of Clinical Investigation [Internet]. 2007 ;117(3):672 - 682. Available from:

People remember prices more easily if they have fewer syllables

The phonological loop — an important component of working memory —can only hold 1.5 to 2 seconds of spoken information. For that reason, faster speakers have an advantage over slower speakers. Now a consumer study reveals that every extra syllable in a product's price decreases its chances of being remembered by 20%. Thus, people who shorten the number of syllables (e.g. read 5,325 as 'five three two five' as opposed to 'five thousand three hundred and twenty five') have better recall. However, since we store information both verbally and visually, it’s also the case that unusual looking prices, such as $8.88, are recalled better than typical looking prices.

Vanhuele, M., Laurent, G., Dreze, X. & Calder, B. 2006. Consumers' Immediate Memory for Prices. Journal of Consumer Research, 33(2), 163-72.

New view of hippocampus’s role in memory

Amnesiacs have overturned the established view of the hippocampus, and of the difference between long-and short-term memories. It appears the hippocampus is just as important for retrieving certain types of short-term memories as it is for long-term memories. The critical thing is not the age of the memory, but the requirement to form connections between pieces of information to create a coherent episode. The researchers suggest that, for the brain, the distinction between 'long-term' memory and 'short-term' memory are less relevant than that between ‘feature’ memory and ‘conjunction’ memory — the ability to remember specific things versus how they are related. The hippocampus may be thought of as the brain's switchboard, piecing individual bits of information together in context.

[817] Olson IR, Page K, Moore KS, Chatterjee A, Verfaellie M. Working Memory for Conjunctions Relies on the Medial Temporal Lobe. J. Neurosci. [Internet]. 2006 ;26(17):4596 - 4601. Available from:

Learning and working memory

A 3-year research project on Working Memory and Cognition has reached its conclusion. The association between effective language learning and good short-term memory is, it seems, not a causal relationship. It is not that a good short-term memory is a prerequisite for long-term learning; it is that both short-term and long-term memory tasks tap the same ability to create representations of sufficient quality to support the maintenance of several of them at once.
Another finding is that metaphoric language often puts greater stress on working memory and so is harder to process than literal language.
Another study looked at differences between the abilities of musicians and persons who did not have music as an active hobby to remember series of notes presented in succession on a computer screen. The results show how expertise makes it possible to apparently bypass working memory limits, even when the memory items cannot be grouped into simple categories.

Discovery disproves simple concept of memory as 'storage space'

The idea of memory “capacity” has become more and more eroded over the years, and now a new technique for measuring brainwaves seems to finally knock the idea on the head. Consistent with recent research suggesting that a crucial problem with aging is a growing inability to ignore distracting information, this new study shows that visual working memory depends on your ability to filter out irrelevant information. Individuals have long been characterized as having a “high” working memory capacity or a “low” one — the assumption has been that these people differ in their storage capacity. Now it seems it’s all about a neural mechanism that controls what information gets into awareness. People with high capacity have a much better ability to ignore irrelevant information.

[1091] Vogel EK, McCollough AW, Machizawa MG. Neural measures reveal individual differences in controlling access to working memory. Nature [Internet]. 2005 ;438(7067):500 - 503. Available from:

How much can your mind keep track of?

A recent study has tried a new take on measuring how much a person can keep track of. It's difficult to measure the limits of processing capacity because most people automatically break down large complex problems into small, manageable chunks. To keep people from doing this, therefore, researchers created problems the test subjects wouldn’t be familiar with. 30 academics were presented with incomplete verbal descriptions of statistical interactions between fictitious variables, with an accompanying set of graphs that represented the interactions. It was found that, as the problems got more complex, participants performed less well and were less confident. They were significantly less able to accurately solve the problems involving four-way interactions than the ones involving three-way interactions, and were completely incapable of solving problems with five-way interactions. The researchers concluded that we cannot process more than four variables at a time (and at that, four is a strain).

[415] Halford GS, Baker R, McCredden JE, Bain JD. How many variables can humans process?. Psychological Science: A Journal of the American Psychological Society / APS [Internet]. 2005 ;16(1):70 - 76. Available from:

Cognitive therapy for ADHD

A researcher that has previously demonstrated that working memory capacity can be increased through training, has now reported that the training software has produced significant improvement in children with ADHD — a disability that is associated with deficits in working memory. The study involved 53 children with ADHD, aged 7-12, who were not on medication for their disability. 44 of these met the criterion of more than 20 days of training. Half the participants were assigned to the working memory training program and the other half to a comparison program. 60% of those who underwent the wm training program no longer met the clinical criteria for ADHD after five weeks of training. The children were tested on visual-spatial memory, which has the strongest link to inattention and ADHD. Further research is needed to show that training improves ability on a wider range of tasks.

[583] Klingberg T, Fernell E, Olesen PJ, Johnson M, Gustafsson P, Dahlström K, Gillberg CG, Forssberg H, Westerberg H. Computerized Training of Working Memory in Children With ADHD-A Randomized, Controlled Trial. Journal of the American Academy of Child & Adolescent Psychiatry [Internet]. 2005 ;44(2):177 - 186. Available from:

Anxiety adversely affects those who are most likely to succeed at exams

It has been thought that pressure harms performance on cognitive skills such as mathematical problem-solving by reducing the working memory capacity available for skill execution. However, a new study of 93 students has found that this applies only to those high in working memory. It appears that the advantage of a high working memory capacity disappears when that attention capacity is compromised by anxiety.

[355] Beilock SL, Carr TH. When high-powered people fail: working memory and "choking under pressure" in math. Psychological Science: A Journal of the American Psychological Society / APS [Internet]. 2005 ;16(2):101 - 105. Available from:

Development of working memory with age

An imaging study of 20 healthy 8- to 30-year-olds has shed new light on the development of working memory. The study found that pre-adolescent children relied most heavily on the prefrontal and parietal regions of the brain during the working memory task; adolescents used those regions plus the anterior cingulate; and in adults, a third area of the brain, the medial temporal lobe, was brought in to support the functions of the other areas. Adults performed best. The results support the view that a person's ability to have voluntary control over behavior improves with age because with development, additional brain processes are used.

Training improves working memory capacity

Working memory capacity has traditionally been thought to be constant. Recent studies, however, suggest that working memory can be improved by training. In this recent imaging study, it was found that adults who practiced working memory tasks for 5 weeks showed increased brain activity in the middle frontal gyrus and superior and inferior parietal cortices. These changes could be evidence of training-induced plasticity in the neural systems that underlie working memory.

Olesen, P.J., Westerberg, H. & Klingberg, T. 2004. Increased prefrontal and parietal activity after training of working memory. Nature Neuroscience, 7(1), 75-9.

Tests for working memory capacity more limited than thought

The so-called “magic number 7” has been a useful mnemonic for working memory capacity — how many items you can hold in your working memory at one time — but we’ve known for some time that it isn’t quite as it was originally thought. Apart from the fact that the “7” is an average, and that the idea of an “item” is awfully vague as far as informational content is concerned, we have known for some time that what is really important is how long it takes for you to say the words. Thus, Chinese can hold on average 9 items, because the words used in the test are short and simple to pronounce, whereas the Welsh can hold only 5 on average, because of the length and complexity of their words. (note: it’s not because we actually say these words out loud). Similarly, the finding that deaf users of American Sign Language have an average of only 5 items was thought to be because signs take longer to utter. However, new research casts doubt on this theory. The researchers were trying to devise a sign-language test that would be comparable to a hearing language test. To their surprise they found that even when signs were faster to pronounce than spoken language, signers recalled only five items. Also, hearing individuals who were fluent in American Sign Language scored differently when asked to recall spoken lists in order, versus when they recalled signed lists (seven heard items remembered, five signed items remembered). Up until this time, the predominant idea was that the number found by this test was a good measure of overall cognitive capacity, but this assumption must now be in doubt. It's suggested that a test requiring recall of items, but not in temporal order, is a better measure of cognitive capacity. The results have important implications for standardized tests, which often employ ordered-list retention as a measure of a person's mental aptitude.

[422] Boutla M, Supalla T, Newport EL, Bavelier D. Short-term memory span: insights from sign language. Nat Neurosci [Internet]. 2004 ;7(9):997 - 1002. Available from:

Hippocampus and subiculum both critical for short-term memory

A new animal study has revealed that the hippocampus shares its involvement in short-term memory with an adjacent brain region, the subiculum. Both regions act together to establish and retrieve short-term memories. The process involves each region acting at different times, with the other region shutting off while the other is active. The shortest memories (10-15s) were found to be controlled almost exclusively by the subiculum. After 15s, the hippocampus took over. It was also found that the hippocampus appeared to respond in a way influenced by previous experiences, allowing it to anticipate future events on the basis of past outcomes. This is an advantage but can also cause errors.

[349] Deadwyler SA, Hampson RE. Differential but Complementary Mnemonic Functions of the Hippocampus and Subiculum. Neuron [Internet]. 2004 ;42(3):465 - 476. Available from:

Why working memory capacity is so limited

There’s an old parlor game whereby someone brings into a room a tray covered with a number of different small objects, which they show to the people in the room for one minute, before whisking it away again. The participants are then required to write down as many objects as they can remember. For those who perform badly at this type of thing, some consolation from researchers: it’s not (entirely) your fault. We do actually have a very limited storage capacity for visual short-term memory.
Now visual short-term memory is of course vital for a number of functions, and reflecting this, there is an extensive network of brain structures supporting this type of memory. However, a new imaging study suggests that the limited storage capacity is due mainly to just one of these regions: the posterior parietal cortex. An interesting distinction can be made here between registering information and actually “holding it in mind”. Activity in the posterior parietal cortex strongly correlated with the number of objects the subjects were able to remember, but only if the participants were asked to remember. In contrast, regions of the visual cortex in the occipital lobe responded differently to the number of objects even when participants were not asked to remember what they had seen.

[598] Todd JJ, Marois R. Capacity limit of visual short-term memory in human posterior parietal cortex. Nature [Internet]. 2004 ;428(6984):751 - 754. Available from: (Telegraph article)

Brain signal predicts working memory capacity

Our visual short-term memory may have an extremely limited capacity, but some people do have a greater capacity than others. A new study reveals that an individual's capacity for such visual working memory can be predicted by his or her brainwaves. In the study, participants briefly viewed a picture containing colored squares, followed by a one-second delay, and then a test picture. They pressed buttons to indicate whether the test picture was identical to -- or differed by one color -- from the one seen earlier. The more squares a subject could correctly identify having just seen, the greater his/her visual working memory capacity, and the higher the spike of corresponding brain activity – up to a point. Neural activity of subjects with poorer working memory scores leveled off early, showing little or no increase when the number of squares to remember increased from 2 to 4, while those with high capacity showed large increases. Subjects averaged 2.8 squares.

[1154] Vogel EK, Machizawa MG. Neural activity predicts individual differences in visual working memory capacity. Nature [Internet]. 2004 ;428(6984):748 - 751. Available from:

Small world networks key to working memory

A computer model may reveal an important aspect of working memory. The key, researchers say, is that the neurons form a "small world" network. In such a network, regardless of its size, any two points within them are always linked by only a small number of steps. Working memory may rely on the same property.

[2547] Micheloyannis S, Pachou E, Stam CJ, Vourkas M, Erimaki S, Tsirka V. Using graph theoretical analysis of multi channel EEG to evaluate the neural efficiency hypothesis. Neuroscience Letters [Internet]. 2006 ;402(3):273 - 277. Available from:

Memory-enhancing drugs for elderly may impair working memory and other executive functions

Drugs that increase the activity of an enzyme called protein kinase A improve long-term memory in aged mice and have been proposed as memory-enhancing drugs for elderly humans. However, the type of memory improved by this activity occurs principally in the hippocampus. A new study suggests that increased activity of this enzyme has a deleterious effect on working memory (which principally involves the prefrontal cortex). In other words, a drug that helps you remember a recent event may worsen your ability to remember what you’re about to do (to take an example).

Ramos, B.P., Birnbaum, S.G., Lindenmayer, I., Newton, S.S., Duman, R.S. & Arnsten, A.F.T. 2003. Dysregulation of Protein Kinase A Signaling in the Aged Prefrontal Cortex: New Strategy for Treating Age-Related Cognitive Decline. Neuron, 40, 835-845.

Sleep deprivation affects working memory

A recent study investigated the working memory capacities of individuals who were sleep-deprived. For nine days, 7 of the 12 participants slept four hours each night, and 5 slept for eight hours. Each morning, participants completed a computer task to measure how quickly they could access a list of numbers they had been asked to memorize. The list could be one, three, or five items long. Then participants were presented with a series of single digits and asked to answer "yes" or "no" to indicate whether each digit was one they had memorized. Those who slept eight hours a night steadily increased their working memory efficiency on this task, but those who slept only four hours a night failed to show any improvement in memory efficiency. Motor skill did not change across days for either group of participants.

Casement, M.D., Mullington, J.M., Broussard, J.L., & Press, D.Z. 2003. The effects of prolonged sleep restriction on working memory performance. Paper presented at the annual meeting of the Society for Neuroscience, New Orleans, LA.

Gesturing reduces cognitive load

Why is it that people cannot keep their hands still when they talk? One reason may be that gesturing actually lightens cognitive load while a person is thinking of what to say. Adults and children were asked to remember a list of letters or words while explaining how they solved a math problem. Both groups remembered significantly more items when they gestured during their math explanations than when they did not gesture.

[1300] Goldin-Meadow S, Nusbaum H, Kelly SD, Wagner S. Explaining math: gesturing lightens the load. Psychological Science: A Journal of the American Psychological Society / APS [Internet]. 2001 ;12(6):516 - 522. Available from:

Stereotype threat

Older news items (pre-2010) brought over from the old website

Positive stereotypes can offset negative stereotype effect

A number of studies have now shown that negative stereotypes can impair cognitive performance, mainly through adding to working memory load. A new study has now shown that this effect can be mitigated by the activation of a positive stereotype. The research takes advantage of the fact that we all belong to several social groups. In this case, the relevant groups were ‘female’ and ‘college student’. As usual, when (subtly) reminded of negative stereotypes for women and math, women performed worse. The interesting thing was that this didn’t happen if women were also made aware that college students performed better at math than non-college students. Moreover, this was reflected in working memory capacity. It seems that, when both a positive and a negative stereotype are offered, people will tend to choose the positive stereotype, and the effects of this will cancel out the negative stereotype. It’s also worth noting how easily these stereotypes are activated: effects could be manipulated simply by subtly changing demographic questions asked before the test (and it is not uncommon that test-takers are first required to answer some demographic questions).

[1381] Rydell RJ, McConnell AR, Beilock SL. Multiple social identities and stereotype threat: Imbalance, accessibility, and working memory. Journal of Personality and Social Psychology [Internet]. 2009 ;96(5):949 - 966. Available from:

Implicit stereotypes and gender identification may affect female math performance

Another study has come out showing that women enrolled in an introductory calculus course who possessed strong implicit gender stereotypes, (for example, automatically associating "male" more than "female" with math ability and math professions) and were likely to identify themselves as feminine, performed worse relative to their female counterparts who did not possess such stereotypes and who were less likely to identify with traditionally female characteristics. Strikingly, a majority of the women participating in the study explicitly expressed disagreement with the idea that men have superior math ability, suggesting that even when consciously disavowing stereotypes, female math students are still susceptible to negative perceptions of their ability.

[969] Kiefer AK, Sekaquaptewa D. Implicit stereotypes, gender identification, and math-related outcomes: a prospective study of female college students. Psychological Science: A Journal of the American Psychological Society / APS [Internet]. 2007 ;18(1):13 - 18. Available from:

Reducing the racial achievement gap

And staying with the same theme, a study that came out six months ago, and recently reviewed on the excellent new Scientific American Mind Matters blog, revealed that a single, 15-minute intervention erased almost half the racial achievement gap between African American and white students. The intervention involved writing a brief paragraph about which value, from a list of values, was most important to them and why. The intervention improved subsequent academic performance for some 70% of the African American students, but none of the Caucasians. The study was repeated the following year with the same results. It is thought that the effect of the intervention was to protect against the negative stereotypes regarding the intelligence and academic capabilities of African Americans.

[1082] Cohen GL, Garcia J, Apfel N, Master A. Reducing the Racial Achievement Gap: A Social-Psychological Intervention. Science [Internet]. 2006 ;313(5791):1307 - 1310. Available from:

Women's math performance affected by theories on sex differences

In a salutary reminder to all researchers into gender and race differences, researchers found that women who received a genetic explanation for female underachievement in math or were reminded of the stereotype about female math underachievement, performed more poorly on math tests than those who received an experiential explanation (such as math teachers treating boys preferentially during the first years of math education) or were led to believe there are no sex differences in math.

[1024] Dar-Nimrod I, Heine SJ. Exposure to Scientific Theories Affects Women's Math Performance. Science [Internet]. 2006 ;314(5798):435 - 435. Available from:

Interactions with other races can impair mental capacity in the strongly prejudiced

A new approach on an old theme — the effect of stress on cognitive function. The study looked at the short-term effects of racial prejudice. White college students were assessed for racial bias and then had a conversation with either a black or white person. After the conversation, they were given the Stroop test (participants are presented with color words, which are either in the same color as they name, or not; they are required to respond on the basis of the color of the word, not the name. The test requires a surprising amount of concentration.) For those who had talked with a black person, the greater the amount of racial bias, the worse the student did on the Stroop test. This is assumed to be due to the stress caused by the interaction.

[833] Richeson JA, Shelton NJ. When prejudice does not pay: Effects of Interracial Contact on Executive Function. Psychological Science [Internet]. 2003 ;14(3):287 - 290. Available from:

Fear & Trauma

See also PTSD

Older news items (pre-2010) brought over from the old website

Scent of fear impacts cognitive performance

A study involving 75 female students found that those who were exposed to chemicals from fear-induced sweat performed more accurately on word-association tasks than did women exposed to chemicals from other types of sweat or no sweat at all. When processing meaningfully related word pairs, the participants exposed to the fear chemicals were significantly more accurate than those in either the neutral sweat or the control (no-sweat) condition. When processing word pairs that were ambiguous in threat content, such as one neutral word paired with a threatening word or a pair of neutral words, subjects in the fear condition were significantly slower in responding than those in the neutral sweat condition.

Chen, D., Katdare, A. & Lucas, N. 2006. Chemosignals of Fear Enhance Cognitive Performance in Humans. Chemical Senses, Advance Access published on March 9, 2006

Memory of fear more complex than supposed

It seems that fear memory is more complex than has been thought. A new mouse study has shown that not only the hippocampus and amygdala are involved, but that the prefrontal cortex is also critical. The development of the fear association doesn’t occur immediately after a distressing event, but develops over time. The process, it now seems, depends directly on a protein called NR2B.

[243] Li B-M, Zhao M-G, Toyoda H, Lee Y-S, Wu L-J, Ko SW, Zhang X-H, Jia Y, Shum F, Xu H. Roles of NMDA NR2B Subtype Receptor in Prefrontal Long-Term Potentiation and Contextual Fear Memory. Neuron [Internet]. 2005 ;47(6):859 - 872. Available from:

How trauma triggers long-lasting memories in the brain

A rat study sheds more light on why emotional experiences tend to be better remembered than emotionally neutral events. The study found that emotionally arousing events activated the amygdala, which then increased a specific protein — activity-regulated cytoskeletal protein ("Arc") — in the neurons in the hippocampus. It's thought that Arc helps store these memories by strengthening the synapses.

[922] McIntyre CK, Miyashita T, Setlow B, Marjon KD, Steward O, Guzowski JF, McGaugh JL. Memory-influencing intra-basolateral amygdala drug infusions modulate expression of Arc protein in the hippocampus. Proceedings of the National Academy of Sciences of the United States of America [Internet]. 2005 ;102(30):10718 - 10723. Available from:

Why traumatic memories have the power they do

In the first imaging study to look at retrieval of emotional memories after a long period (one year after encoding), researchers found that people did recall emotional images, both pleasant and unpleasant, better than emotionally-neutral images. This recall was associated with higher activity in both the amygdala and the hippocampus. The synchronicity of activity between these two regions suggested that each region triggers the other, creating a self-reinforcing "memory loop" in which an emotional cue might trigger recall of the event, which then loops back to a re-experiencing of the emotion of the event. The findings suggest why people subject to traumatic events may be trapped in a cycle of emotion and recall that aggravates post-traumatic stress disorder, and may also suggest why therapies in which people relive such memories and reshape perspective to make it less traumatic can help people cope with such memories.

[198] Dolcos F, LaBar KS, Cabeza R. Remembering one year later: Role of the amygdala and the medial temporal lobe memory system in retrieving emotional memories. Proceedings of the National Academy of Sciences of the United States of America [Internet]. 2005 ;102(7):2626 - 2631. Available from:

Reducing the trauma of traumatic memories

For some, stressful memories can reawaken intense fear, with undesirable consequences. A new study involving mice has found that such stress induces a change in the expression of the acetylcholinesterase gene, which normally produces a vital protein that adheres to neuronal synapses. Following stress, however, the same gene produces large quantities of a protein with modified properties that results in heightened electrical signals in the nerve cells communicating through these synapses. The effect is to create reactions of extreme fright or immobilizing shock. Later encounter with a context which triggers those stressful memories can set off that same neuronal reaction. The researchers have developed an "antisense" agent that acts to neutralize the process whereby the modified protein is produced, thereby preventing the extreme reaction.

[1002] Soreq H, Blank T, Nijholt I, Farchi N, Kye M, Sklan EH, Shoham S, Verbeure B, Owen D, Hochner B, et al. Stress-induced alternative splicing of acetylcholinesterase results in enhanced fear memory and long-term potentiation. Mol Psychiatry [Internet]. 2003 ;9(2):174 - 183. Available from:


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