How the Brain works: Research reports

how the brain works

June 2006

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.
The report appeared in PLoS Biology. Full reference
http://www.eurekalert.org/pub_releases/2006-06/si-cbn060906.htm
Full text available at: http://biology.plosjournals.org/perlserv/?request=get-document&doi=10.1371/journal.pbio.0040207

May 2006

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.
The study was published in the June 1 issue of Neuron. Full reference
http://www.sciencedaily.com/releases/2006/05/060531165250.htm
http://www.eurekalert.org/pub_releases/2006-05/wuso-mpi053006.htm

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.
The report was published in the June issue of Nature Neuroscience. Full reference
http://www.sciencedaily.com/releases/2006/05/060526090336.htm

April 2006

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.
The study was published online April 12 in Nature. Full reference
http://www.yale.edu/opa/newsr/06-04-12-04.all.html

February 2004

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.
The study appeared in the February 6 issue of Cell. Full reference
http://www.eurekalert.org/pub_releases/2004-02/miot-mtd020404.htm

October 2003

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.
The studies appeared in the October 9 issue of Nature. Full reference 2
http://www.eurekalert.org/pub_releases/2003-10/bidm-som100703.htm
http://www.sciencenews.org/20031011/fob4.asp
http://education.guardian.co.uk/higher/research/story/0,9865,1059138,00.html

March 2003

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.
http://www.guardian.co.uk/international/story/0,3604,912940,00.html
http://www.newscientist.com/news/news.jsp?id=ns99993488
http://www.eurekalert.org/pub_releases/2003-03/ns-twf031203.htm

encoding

July 2006

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.
The paper was published in the July edition of Psychological Science. Full reference
http://www.sciencedaily.com/releases/2006/07/060719092800.htm

May 2006

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.
The report appeared in the May 4 issue of Neuron. Full reference
http://www.eurekalert.org/pub_releases/2006-05/cp-tbm042706.htm

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.
The findings were published in the April issue of the Journal of Neuroscience. Full reference
http://origin.www.upenn.edu/pennnews/article.htm?id=963
http://www.eurekalert.org/pub_releases/2006-05/uop-aso053106.htm

February 2006

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.
The study was published online 26 February ahead of print in Nature. Full reference
http://www.nature.com/news/2006/060220/full/060220-19.html
http://www.eurekalert.org/pub_releases/2006-02/uoc--uri022806.htm
http://www.eurekalert.org/pub_releases/2006-02/ucl-ywr022206.htm

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.
The results were published February 7 in the early online edition of the Proceedings of the National Academy of Sciences. Full reference
http://www.eurekalert.org/pub_releases/2006-02/uoc--urp020106.htm

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.
The study was published online 12 February ahead of print in Nature. Full reference
http://www.nature.com/news/2006/060206/full/060206-13.html

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.
The research appeared in two papers in the February 17 issue of Science. Full reference 2
http://www.eurekalert.org/pub_releases/2006-02/hms-rfm022106.htm

September 2005

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.
The study was reported in the September 20 issue of the Proceedings of the National Academy of Sciences. Full reference
Full text is available at: http://tinyurl.com/crnbl
http://www.eurekalert.org/pub_releases/2005-09/uoc--unu090805.htm

May 2004

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.
The research appeared in the May 13 issue of Neuron. Full reference
http://www.eurekalert.org/pub_releases/2004-05/nion-sar051004.htm

February 2004

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, selectingdifferent aspects of the same stimulus image, most likely reflectingdifferent histories, strategies, and expectations residing within individual hippocampal networks.
The findings are reported in the March 2 issue of the Proceedings of the National Academy of Sciences. Full reference
http://www.eurekalert.org/pub_releases/2004-02/wfub-nfo022604.htm

retrieving

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.
The findings were detailed in the December 23 issue of Science. Full reference
http://www.eurekalert.org/pub_releases/2005-12/pu-rdn122205.htm
http://www.eurekalert.org/pub_releases/2005-12/uop-rkw121905.htm

May 2004

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.
The study was published in the May 13 issue of Neuron. Full reference
http://www.eurekalert.org/pub_releases/2004-05/nyu-ssh051204.htm

April 2004

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.
The work was published in the May 7 issue of Science. Full reference
http://news.bbc.co.uk/2/hi/health/3689335.stm

March 2004

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.
The research appeared in the April 2 issue of Cell. Full reference
http://www.eurekalert.org/pub_releases/2004-04/uopm-nii033104.htm

the neural substrate of memory

November 2006

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.
The research is published today in Public Library of Science Biology. Full reference
The full text is available at http://biology.plosjournals.org/perlserv/?request=get-document&doi=10.1371/journal.pbio.0040424
http://www.eurekalert.org/pub_releases/2006-11/wt-tot112406.htm

February 2006

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.
The study was published online 26 February ahead of print in Nature. Full reference
http://www.nature.com/news/2006/060220/full/060220-19.html
http://www.eurekalert.org/pub_releases/2006-02/uoc--uri022806.htm
http://www.eurekalert.org/pub_releases/2006-02/ucl-ywr022206.htm

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.
The results were published February 7 in the early online edition of the Proceedings of the National Academy of Sciences. Full reference
http://www.eurekalert.org/pub_releases/2006-02/uoc--urp020106.htm

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.
The study was published online 12 February ahead of print in Nature. Full reference
http://www.nature.com/news/2006/060206/full/060206-13.html

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.
The research appeared in two papers in the February 17 issue of Science. Full reference 2
http://www.eurekalert.org/pub_releases/2006-02/hms-rfm022106.htm

August 2005

Insight into the processes of 'positive' and 'negative' learners

An intriguing study of the electrical signals emanating from the brain has revealed two types of learners. A brainwave event called an "event-related potential" (ERP) is important in learning; a particular type of ERP called "error-related negativity" (ERN), is associated with activity in the anterior cingulate cortex. This region is activated during demanding cognitive tasks, and ERNs are typically more negative after participants make incorrect responses compared to correct choices. Unexpectedly, studies of this ERN found a difference between "positive" learners, who perform better at choosing the correct response than avoiding the wrong one, and "negative" learners, who learn better to avoid incorrect responses. The negative learners showed larger ERNs, suggesting that "these individuals are more affected by, and therefore learn more from, their errors.” Positive learners had larger ERNs when faced with high-conflict win/win decisions among two good options than during lose/lose decisions among two bad options, whereas negative learners showed the opposite pattern.
The report appeared in the August 18 issue of Neuron. Full reference
http://www.eurekalert.org/pub_releases/2005-08/cp-iit081205.htm

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.
The study was reported in the September 1 issue of Neuron. Full reference
http://www.eurekalert.org/pub_releases/2005-08/cp-tt082505.htm

June 2005

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.
The findings were reported in the June 23 edition of Nature. Full reference
http://www.eurekalert.org/pub_releases/2005-06/uoc--scr062005.htm

May 2005

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.
The findings were presented in the June 1 issue of the Journal of Neuroscience. Full reference
http://www.eurekalert.org/pub_releases/2005-06/nu-bnc060105.htm

April 2005

"Neural cliques" create memories

Typically, brain activity is measured in one or a few neurons at a time. But memory depends on the actions of large sets of neurons. Now a new study has simultaneously recorded the electrical activity of up to 260 individual neurons of the mouse hippocampus in three conditions. Each episode produced different brain activity patterns and identified basic coding units in the hippocampus, “neural cliques”, that respond to the different stimuli. The individual neurons within neural cliques exhibit "collective cospiking" dynamics that allow the neural clique to overcome the response variability of its members and to achieve encoding robustness. These neural cliques provide a plausible neural basis of memory formation.
The study was published in the April 26 issue of the Proceedings of the National Academy of Sciences (USA). Full reference
http://www.eurekalert.org/pub_releases/2005-04/potn-phf041105.htm

Louder neurons form more connections

A study of tiny, see-through zebrafish has provided new insight into how the developing brain chooses which connections to keep. During development, neurons reach out to form many connections, some of which will remain, while others don’t. The study found the decision was based on how “loud” they were — that is, which connections had the most activity compared to other, neighboring connections. The finding could help to explain how early experiences guide brain development.
The study was published in the April 21 issue of Nature Full reference
http://www.eurekalert.org/pub_releases/2005-04/sumc-lnf041805.htm

March 2005

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.
The paper appeared in the March 24 issue of Neuron. Full reference
http://www.eurekalert.org/pub_releases/2005-03/sumc-frv032205.htm

February 2005

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.
The study, available online 12 September 2004, will appear in a forthcoming edition of Intelligence. Full reference
http://www.theaustralian.news.com.au/common/story_page/0,5744,12170249%255E2703,00.html

January 2005

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.
The theory was outlined the in the January issue of Trends in Neuroscience. Full reference
http://www.eurekalert.org/pub_releases/2005-01/nu-ntc011405.htm
http://www.sciencedirect.com/science/journal/01662236

April 2002

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.
The study was reported in April 11 issue of Neuron. Full reference

March 2002

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.
The study was published in the April issue of Nature Neuroscience. Full reference
http://www.eurekalert.org/pub_releases/2002-03/cshl-sef032202.htm
http://news.bbc.co.uk/hi/english/health/newsid_1894000/1894097.stm

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.
The study appeared in the February issue of Nature Neuroscience. Full reference
http://www.eurekalert.org/pub_releases/2002-03/uoh-bcc031202.htm

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).
The report appeared in Cell. Full reference
http://news.bmn.com/news/story?day=020308&story=2
http://news.bbc.co.uk/hi/english/health/newsid_1862000/1862819.stm

January 2002

Individual neurons respond to different aspects of memory

Memories are encoded in patterns of neuronal activation, and these patterns can be widely distributed across the brain. Since recognizing this, we have tended to emphasize the importance of the pattern in storing memory. Does it matter which neurons hold the pattern? Well yes, it appears it does. Technology has reached the point where individual neurons can be identified and their activity monitored. In the latest study, 105 neurons at 57 sites in 26 patients (epileptics undergoing brain surgery to remove those areas of the brain responsible for their seizures) were identified and monitored. It is now clear that neurons are very specialized. For example, researchers identified 16 of the 105 neurons that significantly changed activity with different stages of memory – encoding, storage and retrieval – and found that in 13 of those, changes were observed in only one modality (auditory, six; text, four; objects, three).
The findings appeared in the January issue of Nature Neuroscience. Full reference
http://www.eurekalert.org/pub_releases/2002-01/uow-inr010302.htm

December 2001

Rhythm rather than strength of neural activity may be crucial for memory formation

The strength of the electrical activity between neurons has long been thought to be the critical factor in forming memories, but new research suggests that at least in two critical brain areas, memory may hinge more on the timing than on the strength of neural activity. It seems that, as subjects studied word lists, clusters of neurons in the rhinal cortex and the hippocampus—adjacent brain areas already implicated in memory—fired synchronized electrical bursts that paved the way for remembering those words later. Moreover, the coordination of cell activity in the same two brain regions plummetted for a fraction of a second just after participants remembered a word from the list, possibly signaling an end to a coordinated neural effort. "Memory may emerge when rhinal and hippocampal neurons synchronously oscillate and then desynchronize."
The report is due to appear in the December issue of Nature Neuroscience. Full reference
http://www.sciencenews.org/20011110/fob6.asp
http://news.bmn.com/news/story?day=011105&story=1

November 2001

Pictures show how nerve cells form connections to store memories

Scientists at the University of California, San Diego have produced dramatic images of brain cells forming temporary and permanent connections in response to various stimuli, illustrating for the first time the structural changes between neurons in the brain that, many scientists have long believed, take place when we store short-term and long-term memories.
The report appears in the 30 November issue of Cell. Full reference
http://ucsdnews.ucsd.edu/newsrel/science/mccell.htm

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.
The report appeared in the November 20 issue of the Proceedings of the National Academy of Sciences. Full reference

September 2001

Miniature microscope could monitor activity in individual brain cells

A miniature head-mounted microscope, designed for use on rats, could monitor activity in individual brain cells, says the US team that developed it. The technological breakthrough should, for example, give scientists an unprecedented insight into how memories are formed. Full reference
http://www.newscientist.com/news/news.jsp?id=ns99991353

Manipulating a signaling protein in a developing mouse brain caused radical changes in the cortex and may provide a clue about how the cerebral cortex changes in evolution

Using a newly developed technique, University of Chicago researchers have manipulated one of the signaling proteins in the developing mouse brain and found such manipulations cause radical changes in the cortex. Fibroblast Growth Factor 8 (FGF8), a member of a family of signaling proteins involved in forming other structures in the embryo, is normally found near the front of the developing cortex. Using a new microsurgical technique, the researchers were able to manipulate the amount and position of this signaling protein in the embryo and look for changes in the cortical pattern much later. The researchers increased the amount of the signaling protein in its normal position, decreased it by inserting a gene for a receptor able to soak up the protein, or expressed it in a new position. Each manipulation profoundly affected cortical area pattern. "Most dramatic, when a new source of the signaling protein was generated close to the back of the embryonic cortex, the whole program changed." The generation of a new cortical area by a molecular manipulation has not been seen before and may provide a clue about how the cerebral cortex changes in evolution. One way that evolution seems to generate more functionally complex brains is by adding new areas to the cortex.
The paper appeared In the September 20, 2001 edition of Science Express. Full reference
http://www.eurekalert.org/pub_releases/2001-09/uocm-anm091801.htm