A study involving epilepsy patients who had electrodes implanted into their brain has revealed that memory consolidation during sleep doesn’t simply involve reactivation of the new memories.
A small study has tested the eminent Donald Hebb’s hypothesis that visual imagery results from the reactivation of neural activity associated with viewing images, and that the re-enactment of eye-movement patterns helps both imagery and neural reactivation.
We've all done it: used the wrong name when we know the right one perfectly well. And we all know when it's most likely to happen. But here's a study come to reassure us that it's okay, this is just how we roll.
The study, based on five separate surveys of more than 1,700 respondents, finds that these naming errors (when you call someone you know very well by the wrong name) follow a particular pattern that tells us something about how our memory is organized.
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 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.
August 2009
Analysis of brain scans from 94 people in their 70s who were still "cognitively normal" five years after the scan has revealed that people with higher body mass indexes had smaller brains on average, with the frontal and temporal lobes particularly affected (specifically, in the frontal lobes, anterior cingulate gyrus, hippocampus, and thalamus, in obese people, and in the basal ganglia and corona radiate of the overweight). The brains of the 51 overweight people were, on average, 6% smaller than those of the normal-weight participants, and those of the 14 obese people were 8% smaller. To put it in more comprehensible, and dramatic terms: "The brains of overweight people looked eight years older than the brains of those who were lean, and 16 years older in obese people." However, overall brain volume did not differ between overweight and obese persons. As yet unpublished research by the same researchers indicates that exercise protects these same brain regions: "The most strenuous kind of exercise can save about the same amount of brain tissue that is lost in the obese."
Raji, C.A. et al. 2009. Brain structure and obesity. Human Brain Mapping, Published Online: Aug 6 2009
http://www.newscientist.com/article/mg20327222.400-expanding-waistlines-may-cause-shrinking-brains
May 2009
An imaging study has revealed that daydreaming is associated with an increase in activity in numerous brain regions, especially those regions associated with complex problem-solving. Until now it was thought that the brain's "default network" (which includes the medial prefrontal cortex, the posterior cingulate cortex and the temporoparietal junction) was the only part of the brain active when our minds wander. The new study has found that the "executive network" (including the lateral prefrontal cortex and the dorsal anterior cingulate cortex) is also active. Before this, it was thought that these networks weren’t active at the same time. It may be that mind wandering evokes a unique mental state that allows otherwise opposing networks to work in cooperation. It was also found that greater activation was associated with less awareness on the part of the subject that there mind was wandering.
Christoff, K. et al. 2009. Experience sampling during fMRI reveals default network and executive system contributions to mind wandering. Proceedings of the National Academy of Sciences, 106 (21), 8719-8724.
http://www.eurekalert.org/pub_releases/2009-05/uobc-bpf051109.php
September 2008
Behavioral studies have found eight-year-olds learn primarily from positive feedback, with negative feedback having little effect. Twelve-year-olds, however, are better able to process negative feedback, and use it to learn from their mistakes. Now brain imaging reveals that the brain regions responsible for cognitive control (specifically, the dorsolateral prefrontal cortex and superior parietal cortex, and the pre-supplementary motor area/anterior cingulate cortex) react strongly to positive feedback and scarcely respond at all to negative feedback in children of eight and nine, but the opposite is the case in children of 11 to 13 years, and also in adults.
van Duijvenvoorde, A.C.K. et al. 2008. Evaluating the Negative or Valuing the Positive? Neural Mechanisms Supporting Feedback-Based Learning across Development. The Journal of Neuroscience, 28, 9495-9503.
http://www.eurekalert.org/pub_releases/2008-09/lu-f1y092508.php
http://www.physorg.com/news141554842.html
December 2006
Special elongated nerve cells called spindle neurons, also known as Von Economo neurons (VENs), are found in two parts of the cerebral cortex known to be associated with social behavior, consciousness, and emotion (the anterior cingulate and fronto-insular cortex). They have only been found in humans and great apes, and, recently, whales. Because of this link with social behaviour, and because these brain regions are targeted by frontotemporal dementia, a recent study investigated whether VENs play a role in this type of dementia that causes people to lose inhibition in social situations. Autopsies revealed that among FTD sufferers, the anterior cingulate cortex had a dramatic reduction in the number of VENs compared to controls. In contrast, Alzheimer's patients had only a small and statistically insignificant reduction.
Seeley, W.W. et al. 2006. Early Frontotemporal Dementia Targets Neurons Unique to Apes and Humans. Annals of Neurology, published online ahead of print Decumber 22
http://sciencenow.sciencemag.org/cgi/content/full/2006/1222/1?etoc
http://www.sciencedaily.com/releases/2006/12/061222090935.htm
http://www.eurekalert.org/pub_releases/2006-12/uoc--wih122106.htm
May 2006
Scans of 183 subjects have identified 3 brain areas most consistently active during a variety of cognitive tasks — the dorsal anterior cingulate and the left and right frontal operculum. It’s suggested that these regions coordinate the activities of specialized regions. In a rather lovely analogy, researchers suggested that if the brain in action can be compared to a symphony, with specialized sections required to pitch in at the right time to produce the desired melody, then the regions highlighted by the new study may be likened to conductors. Until now, the function of the opercula has been a mystery; the findings also suggest a rethinking of the role of the cingulate.
Dosenbach, N.U.F. et al. 2006. A core system for the implementation of task sets. Neuron, 50(5), 799-812.
http://www.sciencedaily.com/releases/2006/05/060531165250.htm
http://www.eurekalert.org/pub_releases/2006-05/wuso-mpi053006.php
April 2006
Cognitive impairment in people with AIDS is caused when the HIV virus attacks the brain and can be a complicated syndrome resulting in deficits in mood, behavior, motor coordination and thought processes. While the incidence of severe dementia in people with AIDS has decreased significantly, a greater number of people are living with a milder form of cognitive impairment. A study of 54 participants with AIDS and 23 HIV-negative control subjects has found that cognitive impairment in people with AIDS exists in two forms -- one mild, another severe -- each affecting different areas of the brain. Of the 54 participants with AIDS, 17 demonstrated some level of mental impairment. The mild impairment group only showed problems in the area of psychomotor speed, and demonstrated atrophy in the frontal and anterior cingulate cortices. Those in the severe impairment group showed impairments in memory and visual-spatial processing as well as psychomotor speed, and had more significant atrophy that was located in the caudate and putamen.
The findings were presented April 5 at the American Academy of Neurology 58th Annual Meeting in San Diego.
http://www.eurekalert.org/pub_releases/2006-04/uopm-aci040306.php
February 2006
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.
http://www.eurekalert.org/pub_releases/2006-02/uoc--urp020106.php
November 2005
An imaging study of 15 males aged 26-47 has found that after consuming caffeine, all showed improved reaction times, and increased activity in part of the frontal lobe and in the anterior cingulate cortex. The findings are consistent with earlier research showing caffeine improves attention.
Koppelstätter, F. et al. 2005. Presented at the annual meeting of the Radiological Society of North America in Chicago.
http://www.eurekalert.org/pub_releases/2005-11/rson-cjs112005.php
August 2005
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.
Frank, M.J., Woroch, B.S. & Curran, T. 2005. Error-Related Negativity Predicts Reinforcement Learning and Conflict Biases. Neuron, 47, 495-501.
http://www.eurekalert.org/pub_releases/2005-08/cp-iit081205.php
October 2004
An imaging study has attempted to pinpoint how people form a memory for something that didn't actually happen. The study measured brain activity in people who looked at pictures of objects or imagined other objects they were asked to visualize. Three brain areas (precuneus, right inferior parietal cortex and anterior cingulate) showed greater responses in the study phase to words that would later be falsely remembered as having been presented with photos, compared to words that were not later misremembered as having been presented with photos. Brain activity produced in response to viewed pictures also predicted which pictures would be subsequently remembered. Two brain regions in particular -- the left hippocampus and the left prefrontal cortex -- were activated more strongly for pictures that were later remembered than for pictures that were forgotten. The new findings directly showed that different brain areas are critical for accurate memories for visual objects than for false remembering -- for forming a memory for an imagined object that is later remembered as a perceived object.
Gonsalves, B., Reber, P.J., Gitelman, D.R., Parrish, T.B., Mesulam, M-M. & Paller, K.A. 2004. Neural Evidence That Vivid Imagining Can Lead to False Remembering. Psychological Science, 15 (10), 655-660.
http://www.eurekalert.org/pub_releases/2004-10/nu-nrp101404.php
http://www.northwestern.edu/newscenter/stories/2004/10/kenneth.html
An imaging study of 20 healthy 8- to 30-year-olds has shed new light on the development of working memory. The study found that pre-adolescent children relied most heavily on the prefrontal and parietal regions of the brain during the working memory task; adolescents used those regions plus the anterior cingulate; and in adults, a third area of the brain, the medial temporal lobe, was brought in to support the functions of the other areas. Adults performed best. The results support the view that a person's ability to have voluntary control over behavior improves with age because with development, additional brain processes are used.
http://www.eurekalert.org/pub_releases/2004-10/uopm-dow102104.php
We’re all familiar with that “I know I know it, I just can’t bring it to mind” feeling. Among researchers, this is known as FOK — “feeling of knowing”. It is a common phenomenon, that occurs more frequently as we age. A new imaging study involving a dozen people aged 22 to 32, has investigated the FOK state using pictures of 300 famous and not-so-famous faces. They found that the medial prefrontal cortex showed activity during the FOK state, but not when the subjects either knew or did not know a face. Possibly this reflects a state in which subjects were evaluating the correctness of retrieved information. Additionally, the anterior cingulate area became activated both in the FOK state and when subjects successfully retrieved a name but with some effort. The anterior cingulate area is associated with cognitive conflict processes which allow a person to detect errors in automatic behavior responses. The results suggest that, during a FOK state, the brain may be enlisting additional processes to aid in recalling accurate memories.
http://www.eurekalert.org/pub_releases/2004-10/uoa-cpa102604.php
April 2004
We know that recent memories are stored in the hippocampus, but these memories do not remain there forever. It has been less clear how we retrieve much older memories. Now studies of mice genetically altered to be unable to recall old memories have demonstrated that a part of the cortex called the anterior cingulate is critical for this process. It is suggested that, rather than this structure being the storage site for old memories, the anterior cingulate assembles signals of an old memory from different sites in the brain. Dementia may result from a malfunction in this assembling process, leaving the memory too fragmented to make proper sense. Both ageing and certain aspects of Alzheimer's disease and other dementias are all accompanied by reduced activity in the anterior cingulate.
Frankland, P.W., Bontempi, B., Talton, L.E., Kaczmarek, L. & Silva, A.J. 2004. The Involvement of the Anterior Cingulate Cortex in Remote Contextual Fear Memory. Science, 304, 881-883.
http://news.bbc.co.uk/2/hi/health/3689335.stm
August 2002
An imaging study investigating brain activation when people were asked to answer yes or no to statements about themselves (e.g. 'I forget important things', 'I'm a good friend', 'I have a quick temper'), found consistent activation in the anterior medial prefrontal and posterior cingulate. This is consistent with lesion studies, and suggests that these areas of the cortex are involved in self-reflective thought.
Johnson, S.C., Baxter, L.C., Wilder, L.S., Pipe, J.G., Heiserman, J.E. & Prigatano, G.P. 2002. Neural correlates of self-reflection. Brain, 125 (8), 1808-14.
http://brain.oupjournals.org/cgi/content/abstract/125/8/1808
Because this is such a persistent myth, I thought I should briefly report on this massive study that should hopefully put an end to this myth once and for all (I wish! Myths are not so easily squashed.)
This study used data from 377,000 U.S. high school students, and, agreeing with a previous large study, found that first-borns have a one IQ point advantage over later-born siblings, but while statistically significant, this is a difference of no practical significance.
August 2009
Excessive chronic drinking is known to be associated with deficits in comprehending emotional information, such as recognizing different facial expressions. Now an imaging study of abstinent long-term alcoholics has found that they show decreased and abnormal activity in the amygdala and hippocampus when looking at facial expressions. They also show increased activity in the lateral prefrontal cortex, perhaps in an attempt to compensate for the failure of the limbic areas. The finding is consistent with other studies showing alcoholics invoking additional and sometimes higher-order brain systems to accomplish a relatively simple task at normal levels. The study compared 15 abstinent long-term alcoholics and 15 healthy, nonalcoholic controls, matched on socioeconomic backgrounds, age, education, and IQ.
Marinkovic, K. et al. 2009. Alcoholism and Dampened Temporal Limbic Activation to Emotional Faces. Alcoholism: Clinical and Experimental Research, Published Online: Aug 10 2009
http://www.eurekalert.org/pub_releases/2009-08/ace-edc080509.php
http://www.eurekalert.org/pub_releases/2009-08/bumc-rfa081109.php
June 2009
A study involving 269 patients with mild cognitive impairment provides evidence that a fully automated procedure called Volumetric MRI (that can be done in a clinical setting) can accurately and quickly measure parts of the medial temporal lobe and compare them to expected size. It also found that not only atrophy in the hippocampus but also the amygdala is associated with a greater risk of conversion to Alzheimer’s.
Kovacevic, S. et al. 2009. High-throughput, Fully Automated Volumetry for Prediction of MMSE and CDR Decline in Mild Cognitive Impairment. Alzheimer Disease & Associated Disorders, 23 (2), 139-145.
http://www.eurekalert.org/pub_releases/2009-06/uoc--mba061609.php
December 2008
Another study has found that older adults (average age 70) remember fewer negative images than younger adults (average age 24), and that this has to do with differences in brain activity. When shown negative images, the older participants had reduced interactions between the amygdala and the hippocampus, and increased interactions between the amygdala and the dorsolateral prefrontal cortex. It seems that the older participants were using thinking rather than feeling processes to store these emotional memories, sacrificing information for emotional stability. The findings are consistent with earlier research showing that healthy seniors are able to regulate emotion better than younger people.
St. Jacques, P.L., Dolcos, F. & Cabeza, R. 2009. Effects of Aging on Functional Connectivity of the Amygdala for Subsequent Memory of Negative Pictures: A Network Analysis of Functional Magnetic Resonance Imaging Data. Psychological Science, 20 (1), 74-84.
http://www.eurekalert.org/pub_releases/2008-12/uoaf-aba121608.php
http://www.eurekalert.org/pub_releases/2008-12/dumc-oay121508.php
June 2008
An imaging study of 15 men who smoked more than five cannabis joints daily for more than 10 years has found that, compared with individuals who were not cannabis users, the heavy cannabis users tended to have a smaller hippocampus and amygdala. They also performed significantly worse on verbal learning, but this didn’t correlate with regional brain volumes.
Yücel, M. et al. 2008. Regional Brain Abnormalities Associated With Long-term Heavy Cannabis Use . Archives of General Psychiatry, 65(6), 694-701.
http://www.eurekalert.org/pub_releases/2008-06/usmc-usr061208.php
December 2007
A study of combat-exposed Vietnam War veterans shows that those who suffered injuries to the amygdala or the ventromedial prefrontal cortex were less likely to develop post-traumatic stress disorder than those who suffered damage in other areas or had no head injuries (in fact none of those whose amygdala was damaged developed PTSD). The findings suggest that treatment designed to inhibit the activity of these two areas might provide relief from PTSD.
Koenigs, M. et al. 2007. Focal Brain Damage Protects Against Post-Traumatic Stress Disorder in Combat Veterans. Nature Neuroscience, published on-line December 23
http://www.eurekalert.org/pub_releases/2007-12/nion-sss122107.php
September 2006
An imaging study has revealed that the amygdala and the hippocampus become activated when a person is anticipating a difficult situation (some type of gruesome picture). Moreover, the higher the level of activation during this anticipation, the better the pictures were remembered two weeks later. The study demonstrates how expectancy can affect long-term memory formation, and suggests that the greater our anxiety about a situation, the better we’ll remember that situation. If it’s an unpleasant one, this will only reinforce the anxiety, setting up a vicious cycle. The study has important implications for the treatment of psychological conditions such as post-traumatic stress disorder and social anxiety.
Mackiewicz, K.L., Sarinopoulos, I., Cleven, K.L. & Nitschke, J.B. 2006. The effect of anticipation and the specificity of sex differences for amygdala and hippocampus function in emotional memory. PNAS, 103, 14200-14205.
http://www.eurekalert.org/pub_releases/2006-09/uow-apa090106.php
February 2006
We know emotion can interfere with cognitive processes. Now an imaging study adds to our understanding of how that occurs. Emotional images evoked strong activity in typical emotional processing regions (amygdala and ventrolateral prefrontal cortex) while simultaneously deactivating regions involved in memory processing (dorsolateral prefrontal cortex and lateral parietal cortex). The researchers also found individual differences among the subjects in their response to the images. People who showed greater activity in a brain region associated with the inhibition of response to emotional stimuli rated the emotional distracters as less distracting.
Dolcos, F. & McCarthy, G. 2006. Brain Systems Mediating Cognitive Interference by Emotional Distraction. Journal of Neuroscience, 26, 2072-2079.
http://www.eurekalert.org/pub_releases/2006-02/dumc-he021506.php
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.
http://www.eurekalert.org/pub_releases/2006-02/uoc--urp020106.php
September 2005
It seems that fear memory is more complex than has been thought. A new mouse study has shown that not only the hippocampus and amygdala are involved, but that the prefrontal cortex is also critical. The development of the fear association doesn’t occur immediately after a distressing event, but develops over time. The process, it now seems, depends directly on a protein called NR2B.
Zhao, M-G. et al. 2005. Roles of NMDA NR2B Subtype Receptor in Prefrontal Long-Term Potentiation and Contextual Fear Memory. Neuron, 47, 859-872.
http://www.eurekalert.org/pub_releases/2005-09/uot-sco091505.php
July 2005
A rat study sheds more light on why emotional experiences tend to be better remembered than emotionally neutral events. The study found that emotionally arousing events activated the amygdala, which then increased a specific protein — activity-regulated cytoskeletal protein ("Arc") — in the neurons in the hippocampus. It's thought that Arc helps store these memories by strengthening the synapses.
McIntyre, C.K., Miyashita, T., Setlow, B., Marjon, K.D., Steward, O., Guzowski, J.F. & McGaugh, J.L. 2005. Memory-influencing intra-basolateral amygdala drug infusions modulate expression of Arc protein in the hippocampus. Proceedings of the National Academy of Sciences, 102 (30), 10718-10723.
http://www.eurekalert.org/pub_releases/2005-07/uoc--nih072505.php
February 2005
In the first imaging study to look at retrieval of emotional memories after a long period (one year after encoding), researchers found that people did recall emotional images, both pleasant and unpleasant, better than emotionally-neutral images. This recall was associated with higher activity in both the amygdala and the hippocampus. The synchronicity of activity between these two regions suggested that each region triggers the other, creating a self-reinforcing "memory loop" in which an emotional cue might trigger recall of the event, which then loops back to a re-experiencing of the emotion of the event. The findings suggest why people subject to traumatic events may be trapped in a cycle of emotion and recall that aggravates post-traumatic stress disorder, and may also suggest why therapies in which people relive such memories and reshape perspective to make it less traumatic can help people cope with such memories.
Dolcos, F., LaBar, K.S. & Cabeza, R. 2005. Remembering one year later: Role of the amygdala and the medial temporal lobe memory system in retrieving emotional memories. PNAS, 102 (7), 2626-2631.
http://www.eurekalert.org/pub_releases/2005-03/du-ems030805.php
March 2004
An imaging study has found that words representing arousing events (e.g., “rape”, “slaughter”) activate cells in the amygdala, while nonarousing words (e.g., “sorrow”, “mourning”) activated cells in the prefrontal cortex. The hippocampus was active for both type of words. On average, people remembered more of the arousing words than the others, suggesting stress hormones, released as part of the response to emotionally arousing events, are responsible for enhancing memories of those events.
Kensinger, E.A. & Corkin, S. 2004. Two routes to emotional memory: Distinct neural processes for valence and arousal. PNAS, 101, 3310-3315. Published online before print February 23 2004, 10.1073/pnas.0306408101
http://www.eurekalert.org/pub_releases/2004-03/miot-mlu030104.php
August 2003
Rat studies have now shown that the amygdala supports the formation of new associations by changing nerve cell firing patterns in a different but connected part of the brain. In earlier studies, the researchers had demonstrated that nerve cells in the amygdala and the orbitofrontal cortex changed their firing patterns to reflect new associations between cues and outcomes. In this later study, they examined how changes in neural activity in amygdala might be supporting changes in the orbitofrontal cortex. Rats were first deprived of water, then repeatedly given either desirable drinking water, laced with sugar, or undesirable drinking water, laced with quinine. The associations then learned would show up in the orbitofrontal cortex when the rats smelled the odor cue. The same activation patterns did not however, show up in those rats who had their amygdala chemically lesioned (although these rats still learned to avoid the undesirable drinking water). Specifically, although lesioned rats had neurons in the orbitofrontal cortex that were responsive to the odor cues, they did not have neurons that were responsive in anticipation of the predicted outcome. The responsive neurons were also less associative, more responsive to the identity of the cue rather than the association betwen odor and consequence.
Schoenbaum, G., Setlow, B., Saddoris, M.P. & Gallagher, M. 2003. Encoding Predicted Outcome and Acquired Value in Orbitofrontal Cortex during Cue Sampling Depends upon Input from Basolateral Amygdala. Neuron, 39, 855-867.
http://www.eurekalert.org/pub_releases/2003-08/jhu-kbl082803.php
April 2002
It has long been felt that learning and memory must require physical changes in neurons that increase their responsivity to other neurons, so that they will continue to respond in the long-term even in the absence of external stimuli. Until now, however, noone has been able to actually demonstrate that this long-term potentiation occurs during learning. A new direction has proved to be more successful. Investigation of changes in the amygdala (a part of the brain associated with emotional response) after rats had been trained to fear a sound, found that postsynaptic neurons in the amygdala failed to produce any noticeable increase in electrical current, suggesting they had already been potentiated by their presynaptic partners.
Tsvetkov, E., Carlezon Jr.,W.A., Benes, F.M., Kandel, E.R. & Bolshakov, V.Y. 2002. Fear Conditioning Occludes LTP-Induced Presynaptic Enhancement of Synaptic Transmission in the Cortical Pathway to the Lateral Amygdala. Neuron, 34, 289-300.
May 2001
We choose what to pay attention to, what to remember. We give more weight to some things than others. Our perceptions and memories of events are influenced by our preconceptions, and by our moods. Researchers at Yale and New York University have recently published research indicating that the part of the brain known as the amygdala is responsible for the influence of emotion on perception. This builds on previous research showing that the amygdala is critically involved in computing the emotional significance of events. The amygdala is connected to those brain regions dealing with sensory experiences, and the theory that these connections allow the amygdala to influence early perceptual processing is supported by this research. Dr. Anderson suggests that “the amygdala appears to be critical for the emotional tuning of perceptual experience, allowing perception of emotionally significant events to occur despite inattention.”
Anderson, A.K. & Phelps, E.A. 2001. Lesions of the human amygdala impair enhanced perception of emotionally salient events. Nature, 411, 305-309.
http://www.eurekalert.org/pub_releases/2001-05/NYU-Infr-1605101.php
The number of items a person can hold in short-term memory is strongly correlated with their IQ. But short-term memory has been recently found to vary along another dimension as well: some people remember (‘see’) the items in short-term memory more clearly and precisely than other people. This discovery has lead to the hypothesis that both of these factors should be considered when measuring working memory capacity. But do both these aspects correlate with fluid intelligence?
The ‘resting state’ of the brain is characterized by spontaneous brain activity that has not been understood. Now a new study involving 14 volunteers has found that learning a new task causes measurable changes in that activity, and the degree of change reflects how well subjects have learned to perform the task. The volunteers’ brains were scanned while they were doing nothing, during their learning of a visual task, and afterward, while they did nothing. During the task, part of the visual cortex and frontal-parietal areas involved in the control of spatial attention were particularly active. After learning the task over 5-7 days, during the ‘resting state’ each of these two regions was more likely to be active when the other region wasn't. Subjects who were more successful at the task exhibited a higher degree of this "anti-correlation".
Lewis, C. M., Baldassarre, A., Committeri, G., Romani, G. L., & Corbetta, M. (2009). Learning sculpts the spontaneous activity of the resting human brain. Proceedings of the National Academy of Sciences, 106(41), 17558-17563. doi: 10.1073/pnas.0902455106.
http://www.eurekalert.org/pub_releases/2009-10/wuso-csl100809.php
Research has concentrated on the effects of learning on gray matter, but in a new study involving 24 right-handed volunteers given 6 weeks of training in juggling, white matter was also investigated. It was found that there was not only changes in gray matter in a part of the parietal lobe associated with spatial coordination, but also the myelin in the same region appeared thicker. The gains in both were eroded after four weeks of no juggling. The findings indicate that gray matter and white matter are more interdependent than thought.
Presented at the 15th Annual Meeting of the Organization for Human Brain Mapping held in San Francisco June 18-23.
http://www.the-scientist.com/news/display/55830/
We know circadian rhythm affects learning and memory in that we find it easier to learn at certain times of day than others, but now a study involving Siberian hamsters has revealed that having a functioning circadian system is in itself critical to being able to remember. The finding has implications for disorders such as Down syndrome and Alzheimer's disease. The critical factor appears to be the amount of the neurotransmitter GABA, which acts to inhibit brain activity. The circadian clock controls the daily cycle of sleep and wakefulness by inhibiting different parts of the brain by releasing GABA. It seems that if it’s not working right, if the hippocampus is overly inhibited by too much GABA, then the circuits responsible for memory storage don't function properly. The effect could be fixed by giving a GABA antagonist, which blocks GABA from binding to synapses. Recent mouse studies have also demonstrated that mice with symptoms of Down syndrome and Alzheimer's also show improved learning and memory when given the same GABA antagonist. The findings may also have implications for general age-related cognitive decline, because age brings about a degradation in the circadian system. It’s also worth noting that the hamsters' circadian systems were put out of commission by manipulating the hamsters' exposure to light, in a technique that was compared to "sending them west three time zones." The effect was independent of sleep duration.
Ruby, N.F. et al 2008. Hippocampal-dependent learning requires a functional circadian system. Proceedings of the National Academy of Sciences, 105 (40), 15593-15598.
http://www.eurekalert.org/pub_releases/2008-10/su-ccm100808.php
Gamma waves are fast, high-frequency brainwaves that spike when higher cognitive processes are engaged. Research suggests that lower levels of gamma power might hinder the brain's ability to bind thoughts together. In the first study of the "resting" gamma power in the frontal cortex in young children (16, 24 and 36 months old), it’s been revealed that those with higher language and cognitive abilities had correspondingly higher gamma power than those with poorer language and cognitive scores. Children with better attention and inhibitory control also had higher gamma power. There were no differences in gamma power based on gender or socio-economic status, but children with a family history of language impairments showed lower levels of gamma activity. The finding may enable more accurate pinpointing of a child’s development, enabling earlier, and better targeted, intervention.
Benasich, A.A. et al. 2008. Early cognitive and language skills are linked to resting frontal gamma power across the first 3 years. Behavioral Brain Research, 195 (2), 215-222.
http://www.eurekalert.org/pub_releases/2008-10/ru-teo102108.php
A new mouse study has revealed not only the mechanism for learning deficits resulting from neurofibromatosis type 1, but also something fundamental about learning. It seems that the deficits in learning experienced by mice with an abnormal version of the Nf1 gene stem from an increased release by inhibitory neurons of the inhibitory neurotransmitter GABA. Moreover, the learning deficits can be reversed with treatments that reign GABA levels back in. The study also found show that GABA levels normally swell when mice learn, suggesting that a balance of GABA, a balance between excitatory and inhibitory signals, may be key. Changes in GABA inhibition have also recently been implicated in an animal model of Down's syndrome.
Cui, Y. et al. 2008. Neurofibromin Regulation of ERK Signaling Modulates GABA Release and Learning. Cell, 135 (3), 549-560.
http://www.eurekalert.org/pub_releases/2008-10/cp-sol102408.php
In a truly serendipitous and surprising development, experimental brain surgery intended to suppress an obese man's appetite using the increasingly successful technique of deep-brain stimulation, induced an intense recollection of an event from his distant past. More tests showed his ability to learn was dramatically improved when the current was switched on and his brain stimulated. Scientists are now applying the technique in the first trial of the treatment in 6 patients with Alzheimer's disease. The effect is surprising in that it involves stimulation of the hypothalamus, a critical region for metabolic regulation, but not one that has ever been associated with memory. However, the best contact was in a place close to the fornix, an arched bundle of fibres that carries signals within the limbic system, which is involved in memory and emotions and is situated next to the hypothalamus. Deep brain stimulation has been used for some time to treat Parkinson’s disease and other movement disorders.
Hamani, C. et al. 2008. Memory Enhancement Induced by Hypothalamic/Fornix Deep Brain Stimulation. Annals of Neurology, 63 (1), 119-123.
http://www.independent.co.uk/news/science/scientists-discover-way-to-reverse-loss-of-memory-775586.html
http://www.eurekalert.org/pub_releases/2008-01/w-dbs012408.php
Previous research has shown a large number of brain regions (39) that are consistently active when people prepare for a mental task. It’s been assumed that all these regions work together under the command of one single region. A new study, however, indicates that there are actually two independent networks operating. The cingulo-opercular network (including the dorsal anterior cingulate/medial superior frontal cortex, anterior insula/frontal operculum, and anterior prefrontal cortex) is linked to a "sustain" signal — it turns on at the beginning, hums away constantly during the task, then turns off at the end. In contrast, the frontoparietal network (including the dorsolateral prefrontal cortex and intraparietal sulcus) is active at the start of mental tasks and during the correction of errors. The findings may help efforts to understand the effects of brain injury and develop new strategies to treat such injuries.
Dosenbach, N.U.F. et al. 2007. Distinct brain networks for adaptive and stable task control in humans. Proceedings of the National Academy of Sciences, 104 (26), 11073-11078.
http://www.physorg.com/news101478606.html
New research suggests that the hippocampus makes predictions of what will happen next by automatically recalling an entire sequence of events in response to a single cue, allowing us to anticipate future events and detect when things do not turn out as expected. Rather than reacting to novelty, the hippocampus seems to act as a comparison device, matching up past and present experience.
Kumaran, D. & Maguire, E.A. 2006. An unexpected sequence of events: Mismatch detection in the human hippocampus. PLoS Biol 4(12): e424. DOI: 10.1371/journal.pbio.0040424
The full text is available at http://biology.plosjournals.org/perlserv/?request=get-document&doi=10.1371/journal.pbio.0040424
http://www.eurekalert.org/pub_releases/2006-11/wt-tot112406.php
Synapses — the connections between brain cells — have long been known to be important in information-processing, but the exact nature of their role has not been clear. Are they a crucial part of the processing itself, or simply part of the transport system? Worryingly, research has suggested that synapses drop up to 90% of all incoming signals — an unreliability difficult to reconcile with the fact that brain as a whole is very reliable. A new study has cast new light on synaptic activity. It turns out that synaptic transmission is highly temperature-dependent. Previous studies had studied isolated groups of neurons at room temperature; the present study recorded data at wormer conditions — almost body temperature. And revealed that excitatory and inhibitory synapses, previously thought to always work against each other, in fact act in concert to identify patterns carrying relevant information in an incoming signal. As a result, meaningful patterns are amplified, and stray noise is discarded. This provides the experimental confirmation needed, for the view that synapses act to filter the “noise” and makes the information processing reliable.
Klyachko,V.A. & Stevens, C.F. 2006. Excitatory and Feed-Forward Inhibitory Hippocampal Synapses Work Synergistically as an Adaptive Filter of Natural Spike Trains. PLoS Biology, 4 (7), DOI: 10.1371/journal.pbio.0040207 Full text available at: http://biology.plosjournals.org/perlserv/?request=get-document&doi=10.1371/journal.pbio.0040207
http://www.eurekalert.org/pub_releases/2006-06/si-cbn060906.php
Scans of 183 subjects have identified 3 brain areas most consistently active during a variety of cognitive tasks — the dorsal anterior cingulate and the left and right frontal operculum. It’s suggested that these regions coordinate the activities of specialized regions. In a rather lovely analogy, researchers suggested that if the brain in action can be compared to a symphony, with specialized sections required to pitch in at the right time to produce the desired melody, then the regions highlighted by the new study may be likened to conductors. Until now, the function of the opercula has been a mystery; the findings also suggest a rethinking of the role of the cingulate.
Dosenbach, N.U.F. et al. 2006. A core system for the implementation of task sets. Neuron, 50(5), 799-812.
http://www.sciencedaily.com/releases/2006/05/060531165250.htm
http://www.eurekalert.org/pub_releases/2006-05/wuso-mpi053006.php
A new finding has added to our understanding of how brain cells communicate. A protein called syndapin, previously thought to have no major role in nerve communication, has proven to be the molecule that works with a key protein called dynamin to allow the transmission of messages between nerve cells. The finding has implications for the treatment of many neurological disorders.
Anggono, V. et al. 2006. Syndapin I is the phosphorylation-regulated dynamin I partner in synaptic vesicle endocytosis. Nature Neuroscience, 9, 752 – 760.
http://www.sciencedaily.com/releases/2006/05/060526090336.htm
Although we knew that the release of neurotransmitters at the synapses of neurons causes the voltage inside the neuron to fluctuate continuously — an analog signal — it’s always been thought that the axon was impassable to those fluctuations, and thus that neurons can only communicate with each other through a digital code — that is, by sending out signals whose information is reading in the timing of the pulses. A new study now suggests that the analog signal can indeed travel along the axon, and that the digital signal passed between synapses is influenced by that analog signal. The discovery may lead to a better understanding of disorders such as epilepsy and migraine, both of which involve large changes in the voltage inside neurons.
Shu, Y., Hasenstaub, A., Duque, A., Yu, Y. & McCormick, D.A. 2006. Modulation of intracortical synaptic potentials by presynaptic somatic membrane potential. Nature, advance online publication 12 April 2006.
Previous research has indicated that recognizing a familiar object is accompanied by a reduction in activity in the medial temporal lobe. A new imaging study has confirmed the reduced activity and demonstrated that the degree of reduction is correlated with the degree of familiarity of the object (a face in this instance). The reduction began very rapidly in the recognition process. The researchers suggested that the graded response of medial temporal structures are what allows us to assess how familiar an object is.
Gonsalves, B.D., Curran, T., Norman, K.A. & Wagner, A.D. 2005. Memory Strength and Repetition Suppression: Multimodal Imaging of Medial Temporal Cortical Contributions to Recognition. Neuron, 47, 751–761.
http://www.eurekalert.org/pub_releases/2005-08/cp-tt082505.php
An intriguing study surprises cognitive researchers by showing that individual neurons in the medial temporal lobe are able to recognize specific people and objects. It’s long been thought that concepts such as these require a network of cells, and this doesn’t deny that many cells are involved. However, this new study points to the importance of a single brain cell. The study of 8 epileptic subjects found variable responses from subjects, but within subjects, individuals showed remarkably specific responses to concepts. For example, a single neuron in the left posterior hippocampus of one subject responded to all pictures of actress Jennifer Aniston, and also to Lisa Kudrow, her co-star on the TV hit "Friends", but not to pictures of Jennifer Aniston together with actor Brad Pitt, and not, or only very weakly, to other famous and non-famous faces, landmarks, animals or objects. In another patient, pictures of actress Halle Berry activated a neuron in the right anterior hippocampus, as did a caricature of the actress, images of her in the lead role of the film "Catwoman," and a letter sequence spelling her name. The results suggest an invariant, sparse and explicit code, which might be important in the transformation of complex visual percepts into long-term and more abstract memories.
Quiroga, R.Q., Reddy, L., Kreiman, G., Koch, C & Fried, I. 2005. Invariant visual representation by single neurons in the human brain. Nature, 435, 1102-1107.
http://www.eurekalert.org/pub_releases/2005-06/uoc--scr062005.php
Using a newly released method to analyze functional magnetic resonance imaging, researchers have demonstrated that the interconnections between different parts of the brain are dynamic and not static. Moreover, the brain region that performs the integration of information shifts depending on the task being performed. The study involved two language tasks, in which subjects were asked to read individual words and then make a spelling or rhyming judgment. Imaging showed that the lateral temporal cortex (LTC) was active for the rhyming task, while the intraparietal sulcus (IPS) was active for the spelling task. The inferior frontal gyrus (IFG) and the fusiform gyrus (FG) were engaged by both tasks. However, Dynamic Causal Modeling (the new method for analyzing imaging data) revealed that the network took different configurations depending on the goal of the task, with each task preferentially strengthening the influences converging on the task-specific regions (LTC for rhyming, IPS for spelling). This suggests that task specific regions serve as convergence zones that integrate information from other parts of the brain. Additionally, switching between tasks led to changes in the influence of the IFG on the task-specific regions, suggesting the IFG plays a pivotal role in making task-specific regions more or less sensitive. This is consistent with previous studies showing that the IFG is active in many different language tasks and plays a role in integrating brain regions.
Bitan, T., Booth, J.R., Choy, J., Burman, D.D., Gitelman, D.R. & Mesulam, M-M. 2005. Shifts of Effective Connectivity within a Language Network during Rhyming and Spelling. Journal of Neuroscience, 25, 5397-5403.
http://www.eurekalert.org/pub_releases/2005-06/nu-bnc060105.php
New technology and a small see-through fish called a zebra fish have enabled researchers to watch individual neurons mature. Monitoring the hundreds of neurons in the region of the brain that respond to images, the researchers expected to find that young neurons fire in response to a variety of different images, then refine their role over time so that in the adult fish the neurons only respond to images moving in a certain direction or near the left or right side of the visual field. Instead they found that the neurons fired when they sensed only one type of movement as soon as the neurons were old enough to respond to the images. However, they did take time to establish stable connections. Young neurons send out branches in all directions in the hopes that some branches will connect to other neurons and form synapses that transfer information. As the neuron matures, some of these branches form stable synapses while others recede. This trial-and-error process is what establishes the final interconnected mesh of the brain.
Niell, C.M. &Smith, S.J. 2005. Functional Imaging Reveals Rapid Development of Visual Response Properties in the Zebrafish Tectum. Neuron, 45, 941-951.
http://www.eurekalert.org/pub_releases/2005-03/sumc-frv032205.php
A study of 186 male and 201 female students (aged 18-25) has found that men's brain cells can transmit nerve impulses 4% faster than women's, probably due to the faster increase of white matter in the male brain during adolescence.
Reed, T.E., Vernon, P.A. & Johnson, A.M. 2005. Confirmation of correlation between brain nerve conduction velocity and intelligence level in normal adults. Intelligence, In Press, Corrected Proof, Available online 12 September 2004
http://www.theaustralian.news.com.au/common/story_page/0,5744,12170249%255E2703,00.html
The current view of long-term memory storage is that, at the molecular level, new proteins are manufactured (a process known as translation), and these newly synthesized proteins subsequently stabilize the changes underlying the memory. Thus, every new memory results in a permanent representation in the brain. A new theory of memory storage suggests instead that there is no permanent representation. Rather, memories are copied across many different brain networks. The advantage is that it is a highly flexible system, enabling rapid retrieval even of infrequent elements.
The theory suggests that the brain stores long-term memory by rapidly changing the shape of proteins already present at those synapses activated by learning. The theory explains a number of phenomena that are not properly answered by the existing theory. The theory doesn’t disagree with the view that it is the synapse that is modified in response to learning; the disagreement concerns how that synaptic modification occurs. Current theory says it is brought about by recently synthesized proteins; the new theory suggests that learning leads to a post-synthesis (post-translational) synaptic protein modification that results in changes to the shape, activity and/or location of existing synaptic proteins. It is suggested that long-term memory storage relies on a positive-feedback rehearsal system that continually updates or fine-tunes post-translational modification of previously modified synaptic proteins, thus allowing for the continual modifications of memories.
Routtenberg, A. & Rekart, J.L. 2005. Post-translational protein modification as the substrate for long-lasting memory. Trends in Neurosciences, 28 (1), 12-19.
http://www.eurekalert.org/pub_releases/2005-01/nu-ntc011405.php
http://www.sciencedirect.com/science/journal/01662236
Long-term memories are stored in the brain through strengthening of the connections (synapses) between neurons. Researchers have known for many years that neurons must turn on the synthesis of new proteins for long-term memory storage and synaptic strengthening to occur, but the mechanisms by which neurons accomplish these tasks have remained elusive. Now research has identified a crucial molecular pathway that allows neurons to rapidly boost their production of new proteins. The central component of this pathway, an enzyme called "mitogen-activated protein kinase" (MAPK), effectively provides a molecular switch that triggers long-term memory storage by mobilizing the protein synthesis machinery. The research also reveals that activation of MAPK increased production production of a large number of proteins. Many researchers have thought that only a very limited number of proteins are involved in long-term memory formation.
Kelleher, R.J., Govindarajan, A., Jung, H-Y., Kang, H. & Tonegawa, S. 2004. Translational Control by MAPK Signaling in Long-Term Synaptic Plasticity and Memory. Cell, 116, 467-479.
http://www.eurekalert.org/pub_releases/2004-02/miot-mtd020404.php
Two new studies add to our understanding of the effects of sleep on memory. Both studies involved young adults and procedural (skill) learning, and found temporary declines in performance in particular contexts (a brief description of these studies is given here). On the basis of these studies, researchers identified three stages of memory processing: the first stage of memory — its stabilization — seems to take around six hours. During this period, the memory appears particularly vulnerable to being “lost”. The second stage of memory processing — consolidation — occurs during sleep. The third and final stage is the recall phase, when the memory is once again ready to be accessed and re-edited. (see my article on consolidation for more explanation of the processes of consolidation and re-consolidation) The surprising aspect to this is the time it appears to take for memories to initially stabilize. The studies also confirm the role of sleep in the consolidation process.
Walker, M.P., Brakefield, T., Hobson, J.A. & Stickgold, R. 2003. Dissociable stages of human memory consolidation and reconsolidation. Nature, 425, 616-620.
http://www.eurekalert.org/pub_releases/2003-10/bidm-som100703.php
http://education.guardian.co.uk/higher/research/story/0,9865,1059138,00.html
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.php
It has long been felt that learning and memory must require physical changes in neurons that increase their responsivity to other neurons, so that they will continue to respond in the long-term even in the absence of external stimuli. Until now, however, noone has been able to actually demonstrate that this long-term potentiation occurs during learning. A new direction has proved to be more successful. Investigation of changes in the amygdala (a part of the brain associated with emotional response) after rats had been trained to fear a sound, found that postsynaptic neurons in the amygdala failed to produce any noticeable increase in electrical current, suggesting they had already been potentiated by their presynaptic partners.
Tsvetkov, E., Carlezon Jr.,W.A., Benes, F.M., Kandel, E.R. & Bolshakov, V.Y. 2002. Fear Conditioning Occludes LTP-Induced Presynaptic Enhancement of Synaptic Transmission in the Cortical Pathway to the Lateral Amygdala. Neuron, 34, 289-300.
Memory in fruit flies can be improved by boosting the level of a protein called PKM. The research may provide some answers to the burning question of how particular synapses are chosen. While it is generally agreed that memories are stored as changes in the number and strength of the connections between brain neurons (synapses), it has not been known how the particular synapses involved in a memory or learned skill are selected. It is thought that PKM may be involved in a process that 'tags' synapses during memory formation.
Drier, E.A., Tello. M.K., Cowan, M., Wu, P., Blace, N., Sacktor, T.C. & Yin, J.C.P. 2002.Memory enhancement and formation by atypical PKM activity in Drosophila melanogaster. Nature Neuroscience, 5 (4),316–324.
http://www.eurekalert.org/pub_releases/2002-03/cshl-sef032202.php
http://news.bbc.co.uk/hi/english/health/newsid_1894000/1894097.stm
Experiments with rats have demonstrated that levels of transport molecules for glutamate – chemicals that latch on to and “sweep away” glutamate – increase significantly in the period after the onset of long-term potentiation – the process believed to underlie long-term learning. This suggests that the regulation of glutamate uptake by the transport molecules may be important for maintaining the strength of connections among the neurons. Deficiencies in glutamate transporters have been implicated in neurodegenerative diseases such as amyotrophic lateral sclerosis, or Lou Gherig’s disease.
Levenson, J., Weeber, E., Selcher, J.C., Kategaya, L.S., Sweatt, J.D. & Eskin, A. 2002. Long-term potentiation and contextual fear conditioning increase neuronal glutamate uptake. Nature Neuroscience, 5,155–161.
http://www.eurekalert.org/pub_releases/2002-03/uoh-bcc031202.php
Using mice, scientists have identified a key brain protein involved in retaining memories, which could help explain why some things are remembered and some are not. The protein CREB (cAMP response element binding protein) apparently primes brain cells to retain long-term memories. Neurons in mice engineered to express a chimeric CREB protein were found to need a smaller first stimulus to generate a lasting increase in synaptic strength (long-term potentiation).
Barco, A., Alarcon, J.M. & Kandel, E.R. 2002. Expression of Constitutively Active CREB Protein Facilitates the Late Phase of Long-Term Potentiation by Enhancing Synaptic Capture. Cell, 108 (5), 689-703.
http://news.bbc.co.uk/hi/english/health/newsid_1862000/1862819.stm
Learning happens when a brain cell gets stimulated in a way that reduces its ability to respond to a particular brain messenger called glutamate. In the cerebellum there are very large, strangely shaped brain cells called Purkinje cells that receive more connections than other types of neurons and fire 50 times per second even when you're sleeping. These cells are involved in simple motor learning processes. A recent study provides support for an earlier study that found there are fewer receptors for glutamate on the surface of neurons during long-term synaptic depression, by demonstrating that the other three possible causes for this reduced response to glutamate do not occur.
Linden, D.J. 2001.The expression of cerebellar LTD in culture is not associated with changes in AMPA-receptor kinetics, agonist affinity, or unitary conductance. Proc. Natl. Acad. Sci. USA, 98 (24), 14066-14071.