Drawing best encoding strategy

  • Even quick and not particularly skilled sketches make simple information significantly more likely to be remembered, probably because drawing incorporates several factors that are known to improve memorability.

In a series of experiments involving college students, drawing pictures was found to be the best strategy for remembering lists of words.

The basic experiment involved students being given a list of simple, easily drawn words, for each of which they had 40 seconds to either draw the word, or write it out repeatedly. Following a filler task (classifying musical tones), they were given 60 seconds to then recall as many words as possible. Variations of the experiment had students draw the words repeatedly, list physical characteristics, create mental images, view pictures of the objects, or add visual details to the written letters (such as shading or other doodles).

In all variations, there was a positive drawing effect, with participants often recalling more than twice as many drawn than written words.

Importantly, the quality of the drawings didn’t seem to matter, nor did the time given, with even a very brief 4 seconds being enough. This challenges the usual explanation for drawing benefits: that it simply reflects the greater time spent with the material.

Participants were rated on their ability to form vivid mental images (measured using the VVIQ), and questioned about their drawing history. Neither of these factors had any reliable effect.

The experimental comparisons challenge various theories about why drawing is beneficial:

  • that it processes the information more deeply (when participants in the written word condition listed semantic characteristics of the word, thus processing it more deeply, the results were no better than simply writing out the word repeatedly, and drawing was still significantly better)
  • that it evokes mental imagery (when some students were told to mentally visualize the object, their recall was intermediate between the write and draw conditions)
  • that it simply reflects the fact that pictures are remembered better (when some students were shown a picture of the target word during the encoding time, their recall performance was not significantly better than that of the students writing the words)

The researchers suggest that it is a combination of factors that work together to produce a greater effect than the sum of each. These factors include mental imagery, elaboration, the motor action, and the creation of a picture. Drawing brings all these factors together to create a stronger and more integrated memory code.



[4245] Wammes JD, Meade ME, Fernandes MA. The drawing effect: Evidence for reliable and robust memory benefits in free recall. The Quarterly Journal of Experimental Psychology [Internet]. 2016 ;69(9):1752 - 1776. Available from: http://dx.doi.org/10.1080/17470218.2015.1094494


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Improve learning with co-occurring novelty

  • An animal study shows that following learning with a novel experience makes the learning stronger.
  • A human study shows that giving information positive associations improves your memory for future experiences with similar information.

We know that the neurotransmitter dopamine is involved in making strong memories. Now a mouse study helps us get more specific — and suggests how we can help ourselves learn.

The study, involving 120 mice, found that mice tasked with remembering where food had been hidden did better if they had been given a novel experience (exploring an unfamiliar floor surface) 30 minutes after being trained to remember the food location.

This memory improvement also occurred when the novel experience was replaced by the selective activation of dopamine-carrying neurons in the locus coeruleus that go to the hippocampus. The locus coeruleus is located in the brain stem and involved in several functions that affect emotion, anxiety levels, sleep patterns, and memory. The dopamine-carrying neurons in the locus coeruleus appear to be especially sensitive to environmental novelty.

In other words, if we’re given attention-grabbing experiences that trigger these LC neurons carrying dopamine to the hippocampus at around the time of learning, our memories will be stronger.

Now we already know that emotion helps memory, but what this new study tells us is that, as witness to the mice simply being given a new environment to explore, these dopamine-triggering experiences don’t have to be dramatic. It’s suggested that it could be as simple as playing a new video game during a quick break while studying for an exam, or playing tennis right after trying to memorize a big speech.

Remember that we’re designed to respond to novelty, to pay it more attention — and, it seems, that attention is extended to more mundane events that occur closely in time.

Emotionally positive situations boost memory for similar future events

In a similar vein, a human study has found that the benefits of reward extend forward in time.

In the study, volunteers were shown images from two categories (objects and animals), and were financially rewarded for one of these categories. As expected, they remembered images associated with a reward better. In a second session, however, they were shown new images of animals and objects without any reward. Participants still remembered the previously positively-associated category better.

Now, this doesn’t seem in any way surprising, but the interesting thing is that this benefit wasn’t seen immediately, but only after 24 hours — that is, after participants had slept and consolidated the learning.

Previous research has shown similar results when semantically related information has been paired with negative, that is, aversive stimuli.





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Digital media may be changing how you think

  • Reading from a screen may encourage users to focus on concrete details rather than more abstract thinking.

Four studies involving a total of more than 300 younger adults (20-24) have looked at information processing on different forms of media. They found that digital platforms such as tablets and laptops for reading may make you more inclined to focus on concrete details rather than interpreting information more abstractly.

As much as possible, the material was presented on the different media in identical format.

In the first study, 76 students were randomly assigned to complete the Behavior Identification Form on either an iPad or a print-out. The Form assesses an individual's current preference for concrete or abstract thinking. Respondents have to choose one of two descriptions for a particular behavior — e.g., for “making a list”, the choice of description is between “getting organized” or “writing things down”. The form presents 25 items.

There was a marked difference between those filling out the form on the iPad vs on a physical print-out, with non-digital users showing a significantly higher preference for abstract descriptions than digital users (mean of 18.56 vs 13.75).

In the other three studies, the digital format was always a PDF on a laptop. In the first of these, 81 students read a short story by David Sedaris, then answered 24 multichoice questions on it, of which half were abstract and half concrete. Digital readers scored significantly lower on abstract questions (48% vs 66%), and higher on concrete questions (73% vs 58%).

In the next study, 60 students studied a table of information about four, fictitious Japanese car models for two minutes, before being required to select the superior model. While one model was objectively superior in regard to the attributes and attribute rating, the amount of detail means (as previous research has shown) that those employing a top-down “gist” processing do better than those using a bottom-up, detail-oriented approach. On this problem, 66% of the non-digital readers correctly chose the superior model, compared to 43% of the digital readers.

In the final study, 119 students performed the same task as in the preceding study, but all viewed the table on a laptop. Before viewing the table, however, some were assigned to one of two priming activities: a high-level task aimed at activating more abstract thinking (thinking about why they might pursue a health goal), or a low-level task aimed at activating more concrete thinking (thinking about how to pursue the same goal).

Being primed to think more abstractly did seem to help these digital users, with 48% of this group correctly answering the car judgment problem, compared to only 25% of those given the concrete priming activity, and 30% of the control group.

I note that the performance of the control group is substantially below the performance of the digital users in the previous study, although there was no apparent change in the methodology. However, this was not noted or explained in the paper, so I don't know why this was. It does lead me not to put too much weight on this idea that priming can help.

However, the findings do support the view that reading on digital devices does encourage a more concrete style of thinking, reinforcing the idea that we are inclined to process information more shallowly when we read it from a screen.

Of course, this is, as the researchers point out, not an indictment. Sometimes, this is the best way to approach certain tasks. But what it does suggest is that we need to consider what sort of processing is desirable, and modify our strategy accordingly. For example, you may find it helpful to print out material that requires a high level of abstract thinking, particularly if your degree of expertise in the subject means that it carries a high cognitive load.



Kaufman, G., & Flanagan, M. (2016). High-Low Split : Divergent Cognitive Construal Levels Triggered by Digital and Non-digital Platforms. Proceedings of the SIGCHI Conference on Human Factors in Computing Systems, 1–5. doi:10.1145/2858036.2858550 http://dl.acm.org/citation.cfm?doid=2858036.2858550


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Being overweight linked to poorer memory

  • A study of younger adults adds to evidence that higher BMI is associated with poorer cognition, and points to a specific impairment in memory integration.

A small study involving 50 younger adults (18-35; average age 24) has found that those with a higher BMI performed significantly worse on a computerised memory test called the “Treasure Hunt Task”.

The task involved moving food items around complex scenes (e.g., a desert with palm trees), hiding them in various locations, and indicating afterward where and when they had hidden them. The test was designed to disentangle object, location, and temporal order memory, and the ability to integrate those separate bits of information.

Those with higher BMI were poorer at all aspects of this task. There was no difference, however, in reaction times, or time taken at encoding. In other words, they weren't slower, or less careful when they were learning. Analysis of the errors made indicated that the problem was not with spatial memory, but rather with the binding of the various elements into one coherent memory.

The results could suggest that overweight people are less able to vividly relive details of past events. This in turn might make it harder for them to keep track of what they'd eaten, perhaps making overeating more likely.

The 50 participants included 27 with BMI below 25, 24 with BMI 25-30 (overweight), and 8 with BMI over 30 (obese). 72% were female. None were diagnosed diabetics. However, the researchers didn't take other health conditions which often co-occur with obesity, such as hypertension and sleep apnea, into account.

This is a preliminary study only, and further research is needed to validate its findings. However, it's significant in that it adds to growing evidence that the cognitive impairments that accompany obesity are present early in adult life and are not driven by diabetes.

The finding is also consistent with previous research linking obesity with dysfunction of the hippocampus and the frontal lobe.




[4183] Cheke LG, Simons JS, Clayton NS. Higher body mass index is associated with episodic memory deficits in young adults. The Quarterly Journal of Experimental Psychology [Internet]. 2015 :1 - 12. Available from: http://dx.doi.org/10.1080/17470218.2015.1099163


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Concrete thinking may reduce the power of traumatic memories

  • Focusing on concrete details when experiencing a traumatic event may, oddly enough, protect you more from the power of those memories, than if you tried to distance yourself from what you are experiencing.

Can you help protect yourself from the memory of traumatic events? A new study suggests that, by concentrating on concrete details as you live through the event, you can reduce the number of intrusive memories later experienced.

The study, aimed particularly at those who deliberately expose themselves to the risk of PTSD (e.g., emergency workers, military personnel, journalists in conflict zones), involved 50 volunteers who rated their mood before watching several films with traumatic scenes. After the first film, they rated their feelings. For the next four films, half the participants were asked to consider abstract questions, such as why such situations happened. The other half were asked to consider concrete questions, such as what they could see and hear and what needed to be done from that point. Afterward, they gave another rating on their mood. Finally, they were asked to watch a final film in the same way as they had practiced, rating feelings of distress and horror as they had for the first film.

The volunteers were then given a diary to record intrusive memories of anything they had seen in the films for the next week.

Both groups, unsurprisingly, saw their mood decline after the films, but those who had been practicing concrete thinking were less affected, and also experienced less intense feelings of distress and horror when watching the final film. Abstract thinkers experienced nearly twice as many intrusive memories in the following week.

The study follows previous findings that emergency workers who adopted an abstract processing approach showed poorer coping, and that those who processed negative events using abstract thinking experienced a longer period of low mood, compared to those using concrete thinking.

Further study to confirm this finding is of course needed in real-life situations, but this does suggest a strategy that people who regularly experience trauma could try. It is particularly intriguing because, on the face of it, it would seem like quite the wrong strategy. Distancing yourself from the trauma you're experiencing, trying to see it as something less real, seems a more obvious coping strategy. This study suggests it is exactly the wrong thing to do.

It also seems likely that this tendency to use concrete or abstract processing may reflect a more general trait. Self-reported proneness to intrusive memories in everyday life was significantly correlated with intrusive memories of the films. Perhaps we should all think about the way we view the world, and those of us who tend to take a more abstract approach should try paying more attention to concrete details. This is, after all, something I've been recommending in the context of fighting sensory impairment and age-related cognitive decline!

Abstract thinking certainly has its place, but as I've said before, we need flexibility. Effective cognitive management is about tailoring your style of thinking to the task's demands.



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Individuals vary in how they remember events

  • Individuals vary in how vividly they remember the past. A new study links this to differences in brain activity which may reflect a stable trait.
  • The finding also has implications for assessments of age-related cognitive decline.

A study involving 66 healthy young adults (average age 24) has revealed that different individuals have distinct brain connectivity patterns that are associated with different ways of experiencing and remembering the past.

The participants completed an online questionnaire on how well they remember autobiographical events and facts, then had their brains scanned. Brain scans found that those with richly-detailed autobiographical memories had higher mediotemporal lobe connectivity to regions at the back of the brain involved in visual perception, whereas those tending to recall the past in a factual manner showed higher mediotemporal lobe connectivity to prefrontal regions involved in organization and reasoning.

The finding supports the idea that those with superior autobiographical memory have a greater ability or tendency to reinstate rich images and perceptual details, and that this appears to be a stable personality trait.

The finding also raises interesting questions about age-related cognitive decline. Many people first recognize cognitive decline in their increasing difficulty retrieving the details of events. But this may be something that is far more obvious and significant to people who are used to retrieving richly-detailed memories. Those who rely on a factual approach may be less susceptible.


Full text available at http://www.sciencedirect.com/science/article/pii/S0010945215003834



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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.



Full text at http://elifesciences.org/content/4/e10778v2


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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.
Full text at http://dx.plos.org/10.1371/journal.pone.0007486


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 competitivemodel 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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How your brain chunks ‘moments’ into ‘events’

We talk about memory for ‘events’, but how does the brain decide what an event is? How does it decide what is part of an event and what isn’t? A new study suggests that our brain uses categories it creates based on temporal relationships between people, objects, and actions — i.e., items that tend to—or tend not to—pop up near one another at specific times.


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Reactivate if you want to remember

We know sleep helps consolidate memories. Now a new study sheds light on how your sleeping brain decides what’s worth keeping. The study found that when the information that makes up a memory has a high value—associated with, for example, making more money—the memory is more likely to be rehearsed and consolidated during sleep.



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