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

September 2009

New insights into memory without conscious awareness

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

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

http://www.eurekalert.org/pub_releases/2009-09/cp-ycb090309.php

August 2009

Alcoholics show abnormal brain activity when processing facial expressions

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

Study finds autistics better at problem-solving

A study involving 15 autistics and 18 non-autistics, aged 14 to 36 and IQ-matched, has found that while both groups completed patterns in a complex problem-solving test (the widely-used Raven's Standard Progressive Matrices) with equal accuracy, the autistics responded significantly faster, and showed a different pattern of brain activity. Specifically, they showed increased activity in extrastriate areas, and decreased activity in the lateral prefrontal cortex and the medial posterior parietal cortex — suggesting visual processing mechanisms may play a more prominent role in reasoning in autistics. The differences between groups did not appear when participants performed a simpler pattern-matching task.

Soulières, I. et al. 2009. Enhanced visual processing contributes to matrix reasoning in autism. Human Brain Mapping, Published Online June 15.

http://www.eurekalert.org/pub_releases/2009-06/uom-sfa061609.php

May 2009

Brain's problem-solving function at work when we daydream

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

February 2009

Brain activity linked to anticipation revealed

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

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

http://www.eurekalert.org/pub_releases/2009-02/gumc-rcw022509.php

December 2008

Prefrontal cortex activity in poor children like that of stroke victim

An imaging study of 26 normal 9- and 10-year-olds differing only in socioeconomic status has revealed detectable differences in the response of their prefrontal cortex. While not invariant, those from lower socioeconomic levels were more likely to have low frontal lobe response. This is consistent with earlier studies, but is the first to demonstrate the effect when there is no issue of task complexity (the task was very simple; the measure was how fast the child responded to an unexpected novel picture — the response of many from low socioeconomic backgrounds was similar to the response of adults who have had a portion of their frontal lobe destroyed by a stroke). The effect is thought to be due to growing up in cognitively-impoverished and stressful environments, since these have been found to affect the prefrontal cortex in animal studies. Further research is looking into whether these brain differences can be eliminated by training.

Kishiyama, M.M. et al. 2008. Socioeconomic Disparities Affect Prefrontal Function in Children. Journal of Cognitive Neuroscience

http://www.eurekalert.org/pub_releases/2008-12/uoc--esb120208.php

September 2008

Patients who recover well from head injury 'work harder' to perform at same level as healthy people

People who make a full recovery from head injury often report "mental fatigue" and feeling "not quite the same" – even though they scored well on standard cognitive tests. Now brain imaging reveals that even with recovered head injury patients performing as well as matched controls on a series of working memory tests, their brains were working harder — specifically, showing more activity in regions of the prefrontal cortex and posterior cortices. All the patients had diffuse axonal injury, the most common consequence of head injuries resulting from motor vehicle accidents, falls, combat-related blast injuries, and other situations where the brain is rattled violently inside the skull causing widespread disconnection of brain cells.

Turner, G.R. & Levine, B. 2008. Augmented neural activity during executive control processing following diffuse axonal injury. Neurology, 71, 812-818.

http://www.eurekalert.org/pub_releases/2008-09/bcfg-pwr090308.php

April 2008

Intelligence and rhythmic accuracy go hand in hand

And in another perspective on the nature of intelligence, a new study has demonstrated a correlation between general intelligence and the ability to tap out a simple regular rhythm. The correlation between high intelligence and a good ability to keep time, was also linked to a high volume of white matter in the parts of the frontal lobes involved in problem solving, planning and managing time. The finding suggests that the long-established correlation of general intelligence with the mean and variability of reaction time in elementary cognitive tasks, as well as with performance on temporal judgment and discrimination tasks, is a bottom-up connection, stemming from connectivity in the prefrontal regions.

Ullén, F. et al. 2008. Intelligence and variability in a simple timing task share neural substrates in the prefrontal white matter. The Journal of Neuroscience, 28(16), 4238-4243.

http://www.eurekalert.org/pub_releases/2008-04/ki-iar041608.php

August 2007

Maturity brings richer memories

New research suggests adults can remember more contextual details than children, and that this is related to the development of the prefrontal cortex. While in a MRI scanner, 49 volunteers aged eight to 24 were shown pictures of 250 common scenes and told they would be tested on their memory of these scenes. In both children and adults, correct recognition of a scene was associated with higher activation in several areas of the prefrontal cortex and the medial temporal lobe when they were studying the pictures. However, the older the volunteers, the more frequently their correct answers were enriched with contextual detail. These more detailed memories correlated with more intense activation in a specific region of the PFC. A number of studies have suggested that the PFC develops later than other brain regions.

The report appeared in the August 5 advance online edition of Nature Neuroscience.

http://www.eurekalert.org/pub_releases/2007-08/miot-msm080107.php

June 2007

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

Previous research has shown a large number of brain regions (39) that are consistently active when people prepare for a mental task. It’s been assumed that all these regions work together under the command of one single region. A new study, however, indicates that there are actually two independent networks operating. The cingulo-opercular network (including the dorsal anterior cingulate/medial superior frontal cortex, anterior insula/frontal operculum, and anterior prefrontal cortex) is linked to a "sustain" signal — it turns on at the beginning, hums away constantly during the task, then turns off at 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://news.wustl.edu/news/Pages/9639.aspx

March 2007

Prefrontal cortex loses neurons during adolescence

A rat study has found that adolescents lose neurons in the ventral prefrontal cortex in adolescence, with females losing about 13% more neurons than males. Human studies have found gradual reductions in the volume of gray matter in the prefrontal cortex from adolescence to adulthood, but this finding that neurons are actually dying is new, and indicates that the brain reorganizes in a very fundamental way in adolescence. The number of neurons in the dorsal prefrontal cortex didn’t change, although the number of glial cells increased there (while remaining stable in the ventral area). The finding could have implications for understanding disorders that often arise in late adolescence, such as schizophrenia and depression, and why addictions that start in adolescence are harder to overcome than those that begin in adulthood.

Markham, J.A., Morris, J.R. & Juraska, J.M. 2007. Neuron number decreases in the rat ventral, but not dorsal, medial prefrontal cortex between adolescence and adulthood. Neuroscience, 144 (3), 961-968.

http://www.sciencedaily.com/releases/2007/03/070314093257.htm

Disentangling attention

A new study provides more evidence that the ability to deliberately focus your attention is physically separate in the brain from the part that helps you filter out distraction. The study trained monkeys to take attention tests on a video screen in return for a treat of apple juice. When the monkeys voluntarily concentrated (‘top-down’ attention), the prefrontal cortex was active, but when something distracting grabbed their attention (‘bottom-up’ attention), the parietal cortex became active. The electrical activity in these two areas vibrated in synchrony as they signaled each other, but top-down attention involved synchrony that was stronger in the lower-frequencies and bottom-up attention involved higher frequencies. These findings may help us develop treatments for attention disorders.

Buschman, T.J. & Miller, E.K. 2007. Top-Down Versus Bottom-Up Control of Attention in the Prefrontal and Posterior Parietal Cortices. Science, 315 (5820), 1860-1862.

February 2007

Common gene version optimizes thinking but carries a risk

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

Meyer-Lindenberg,A. et al. 2007. Genetic evidence implicating DARPP-32 in human frontostriatal structure, function, and cognition. Journal of Clinical Investigation, 117 (3), 672-682.

http://www.sciencedaily.com/releases/2007/02/070208230059.htm
http://www.eurekalert.org/pub_releases/2007-02/niom-cgv020707.php

January 2007

Neural bottleneck found that thwarts multi-tasking

An imaging study has revealed just why we can’t do two things at once. The bottleneck appears to occur at the lateral frontal and prefrontal cortex and the superior frontal cortex. Both areas are known to play a critical role in cognitive control. These brain regions responded to tasks irrespective of the senses involved, and could be seen to 'queue' neural activity — that is, a response to the second task was postponed until the response to the first was completed. Such queuing occurred when two tasks were presented within 300 milliseconds of each other, but not when the time gap was longer.

Dux, P.E. et al. 2006. Isolation of a Central Bottleneck of Information Processing with Time-Resolved fMRI. Neuron, 52, 1109-1120.

http://www.eurekalert.org/pub_releases/2007-01/vu-nbf011807.php

November 2006

Hormone replacement therapy may improve visual memory of postmenopausal women

A study of 10 postmenopausal women (aged 50-60) found that those taking combined estrogen-progestin hormone therapy for four weeks showed significantly increased activity in the prefrontal cortex when engaged in a visual matching task, compared with those on placebo.

Smith, Y.R. et al. 2006. Impact of Combined Estradiol and Norethindrone Therapy on Visuospatial Working Memory Assessed by Functional Magnetic Resonance Imaging. The Journal of Clinical Endocrinology & Metabolism, 91 (11), 4476-4481.

http://www.eurekalert.org/pub_releases/2006-11/uomh-hrt111606.php

July 2006

Brain Imaging Identifies Best Memorization Strategies

Why do some people remember things better than others? An imaging study has revealed that the brain regions activated when learning vary depending on the strategy adopted. The study involved 29 right-handed, healthy young adults, ages 18-31, all of whom had normal or corrected-to-normal vision and reported no significant neurological history. Participants were given interacting object pair images (such as a turkey seated atop a horse and a banana positioned in the back of a dump truck) and told to study them in anticipation of a memory test. Earlier studies had indicated that while individuals use a variety of strategies to help them memorize new information, the following four strategies were the main strategies:

1) A visual inspection strategy in which participants carefully studied the visual appearance of objects.

2) A verbal elaboration strategy in which individuals constructed sentences about the objects to remember them.

3) A mental imagery strategy in which participants formed interactive mental images of the objects.

4) A memory retrieval strategy in which they thought about the meaning of the objects and/or personal memories associated with the objects.

Both visual inspection and verbal elaboration resulted in improved recall. Imaging revealed that people who often used verbal elaboration had greater activity in a network of regions that included prefrontal regions associated with controlled verbal processing compared to people who used this strategy less frequently. People who often used a visual inspection strategy had greater activity in a network of regions that included an extrastriate region associated with object processing compared to people who used this strategy less frequently.

Kirchhoff, B.A. & Buckner, R.L. 2006. Functional-Anatomic Correlates of Individual Differences in Memory. Neuron, 51, 263-274.

http://www.sciencedaily.com/releases/2006/08/060809082610.htm

May 2006

Planning is goal-, not action-, oriented

Studies in which monkeys were asked to perform a complex task involving several discrete steps have revealed that the brain's "executive" center, in the lateral prefrontal cortex, plans behaviors not by specifying movements required for given actions, but rather the events that will result from those actions.

Mushiake, H. et al. 2006. Activity in the Lateral Prefrontal Cortex Reflects Multiple Steps of Future Events in Action Plans. Neuron, 50, 631–641.

http://www.eurekalert.org/pub_releases/2006-05/cp-tbe051106.php

January 2006

Morning grogginess worse for cognition than sleep deprivation

People who awaken after eight hours of sound sleep have more impaired thinking and memory skills than they do after being deprived of sleep for more than 24 hours. The impairment is worst in the first three minutes, and the most severe effects have generally dissipated by ten minutes, but measurable effects can last up to two hours. This is consistent with reports indicating that cortical areas like the prefrontal cortex take longer to come “online” after sleep than other parts of the brain. The findings have implications for medical, safety and transportation workers who are often called upon to perform critical tasks immediately after waking, as well as for anyone abruptly woken to face an emergency situation.

Wertz, A.T., Ronda, J.M., Czeisler, C.A. & Wright, K.P.Jr. 2006. Effects of Sleep Inertia on Cognition. Journal of the American Medical Association, 295,163-164.

http://www.eurekalert.org/pub_releases/2006-01/uoca-mgm121905.php

Fitness counteracts cognitive decline from hormone-replacement therapy

A study of 54 postmenopausal women (aged 58 to 80) suggests that being physically fit offsets cognitive declines attributed to long-term hormone-replacement therapy. It was found that gray matter in four regions (left and right prefrontal cortex, left parahippocampal gyrus and left subgenual cortex) was progressively reduced with longer hormone treatment, with the decline beginning after more than 10 years of treatment. Therapy shorter than 10 years was associated with increased tissue volume. Higher fitness scores were also associated with greater tissue volume. Those undergoing long-term hormone therapy had more modest declines in tissue loss if their fitness level was high. Higher fitness levels were also associated with greater prefrontal white matter regions and in the genu of the corpus callosum. The findings need to be replicated with a larger sample, but are in line with animal studies finding that estrogen and exercise have similar effects: both stimulate brain-derived neurotrophic factor.

Erickson, K.I., Colcombe, S.J., Elavsky, S., McAuley, E., Korol, D., Scalf, P.E. & Kramer, A.F. 2006. Interactive effects of fitness and hormone treatment on brain health in postmenopausal women. Neurobiology of Aging, In Press, Corrected Proof, Available online 6 January 2006

http://www.eurekalert.org/pub_releases/2006-01/uoia-fcc012406.php

September 2005

Memory of fear more complex than supposed

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

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

June 2005

How sleep improves memory

While previous research has been conflicting, it does now seem clear that sleep consolidates learning of motor skills in particular. A new imaging study involving 12 young adults taught a sequence of skilled finger movements has found a dramatic shift in activity pattern when doing the task in those who were allowed to sleep during the 12 hour period before testing. Increased activity was found in the right primary motor cortex, medial prefrontal lobe, hippocampus and left cerebellum — this is assumed to support faster and more accurate motor output. Decreased activity was found in the parietal cortices, the left insular cortex, temporal pole and fronto-polar region — these are assumed to reflect less anxiety and a reduced need for conscious spatial monitoring. It’s suggested that this is one reason why infants need so much sleep — motor skill learning is a high priority at this age. The findings may also have implications for stroke patients and others who have suffered brain injuries.

Walker, M.P., Stickgold, R., Alsop, D., Gaab, N. & Schlaug, G. 2005. Sleep-dependent motor memory plasticity in the human brain.Neuroscience, 133 (4) , 911-917.

http://www.eurekalert.org/pub_releases/2005-06/bidm-ssh062805.php

March 2005

Primitive brain learns faster than the "thinking" part of our brain

A study of monkeys has revealed that a primitive region of the brain known as the basal ganglia learns rules first, then “trains” the prefrontal cortex, which learns more slowly. The findings turn our thinking about how rules are learned on its head — it has been assumed that the smarter areas of our brain work things out; instead it seems that primitive brain structures might be driving even our most high-level learning.

Pasupathy, A. &Miller, E.K. 2005. Different time courses of learning-related activity in the prefrontal cortex and striatum. Nature, 433, 873-876.

http://news.mit.edu/2005/basalganglia

February 2005

How the brain creates false memories

An imaging study has shed new light on how false memories are formed. The study involved participants watching series of 50 photographic slides that told a story. A little later, the subjects were shown what they thought was the same sequence of slides but in fact containing a misleading item and differing in small ways from the original. Two days later, the subjects’ memories were tested. It was found that, during the original encoding (the 1^st set of slides), activity in the hippocampus and perirhinal cortex was greater for true than for false memories, while during the misinformation phase (2^nd set), the activity there was greater for false memories. In other regions, such as the prefrontal cortex, activity for false memories tended to be greater during the original event. Activity in the prefrontal cortex may be correlated to encoding the source, or context, of the memory. Thus, weak prefrontal cortex activity during the misinformation phase indicates that the details of the second experience were poorly placed in a learning context, and as a result more easily embedded in the context of the first event, creating false memories.

Okado, Y. & Stark, C.E.L. 2005. Neural activity during encoding predicts false memories created by misinformation. Learning & Memory, 12, 3-11.

http://www.eurekalert.org/pub_releases/2005-02/cshl-htb012805.php

October 2004

How false memories are formed

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

Development of working memory with age

An imaging study of 20 healthy 8- to 30-year-olds has shed new light on the development of working memory. The study found that pre-adolescent children relied most heavily on the prefrontal cortex 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

September 2004

New technique sheds light on autobiographical memory

A new technique for studying autobiographical memory has revealed new findings about autobiographical memory, and may prove useful in studying age-related cognitive impairment. Previous inconsistencies between controlled laboratory studies of memory (typically, subjects are asked to remember items they have previously seen in the laboratory, such as words presented on a computer screen) and studies of autobiographical memory have seemed to indicate that the brain may function differently in the two processes. However, such differences might instead reflect how the memories are measured. In an effort to provide greater control over the autobiographical memories, volunteer subjects were given cameras and instructed to take pictures of campus scenes. The subjects were also instructed to remember the taking of each picture as an individual event, noting the physical conditions and their psychological state, such as their mood and associations with the subject of the images. The subjects were then shown a selection of campus photos they had not taken. While their brains were scanned, they were then shown a mix of their own photos with those they had not taken, and asked to indicate whether each photo was new, seen earlier in the lab, or one they had taken themselves. The researchers found that recalling the autobiographical memories activated many of the same brain areas as laboratory memories (the medial temporal lobe and the prefrontal cortex); however, they also activated brain areas associated with "self-referential processing" (processing information about one's self), and regions associated with retrieval of visual and spatial information, as well as showing a higher level of activity in the recollection areas in the hippocampus.

The report appeared in the November issue of the Journal of Cognitive Neuroscience.

http://www.eurekalert.org/pub_releases/2004-09/du-blm092904.php

March 2004

Different brain regions for arousing and non-arousing words

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

January 2004

More evidence for active forgetting

In an imaging study involving 24 people aged 19 to 31, participants were given pairs of words and told to remember some of the matched pairs but forget others. Trying to shut out memory appeared more demanding than remembering, in that some areas of the brain were significantly more when trying to suppress memory. Both the prefrontal cortex and the hippocampus were active. Those whose prefrontal cortex and hippocampus were most active during this time were most successful at suppressing memory.

Anderson, M.C., Ochsner, K.N., Kuhl, B., Cooper, J., Robertson, E., Gabrieli, S.W., Glover, G.H. & Gabrieli, J.D.E. 2004. Neural Systems Underlying the Suppression of Unwanted Memories. Science, 303 (5655), 232-235.

http://www.eurekalert.org/pub_releases/2004-01/su-rrb010604.php

August 2002

How emotions interfere with staying focused

In a new imaging study, Duke University researchers have shown how emotional stimuli and "attentional functions" like driving move in parallel streams through the brain before being integrated in a specific part of the brain's prefrontal cortex (the anterior cingulate, which is located between the right and left halves). Emotional stimuli are thus more likely than simple distractions to interfere with a person's efforts to focus on a task such as driving. These findings may help us understand the neural dynamics underlying emotional distractibility on attentional tasks in affective disorders.

Yamasaki, H., LaBar, K.S. & McCarthy, G. Dissociable prefrontal brain systems for attention and emotion. Proc. Natl. Acad. Sci. USA, 99(17), 11447-51.

http://www.pnas.org/content/99/17/11447.abstract

December 2001

Age-related changes in brain dopamine may underpin the normal cognitive problems of aging

A new model suggests why and how many cognitive abilities decline with age, and offers hope for prevention. Research in the past few years has clarified and refined our ideas about the ways in which cognitive abilities decline with age, and one of these ways is in a reduced ability to recall the context of memories. Thus, for example, an older person is less likely to be able to remember where she has heard something. According to this new model, context processing is involved in many cognitive functions — including some once thought to be independent — and therefore a reduction in the ability to remember contextual information can have wide-reaching implications for many aspects of cognition. The model suggests that context processing occurs in the prefrontal cortex and requires a certain level of the brain chemical dopamine. It may be that in normal aging, dopamine levels become low or erratic. Changes in dopamine have also been implicated in Alzheimer’s, as well as other brain-based diseases.

Braver, T.S., Barch, D.M., Keys, B.A., Carter, C.S., Cohen, J.D., Kaye, J.A., Janowsky, J.S., Taylor, S.F., Yesavage, J.A., Mumenthaler, M.S., Jagust, W.J., & Reed, B.R. 2001. Context Processing in Older Adults: Evidence for a Theory Relating Cognitive Control to Neurobiology in Healthy Aging. Journal of Experimental Psychology –General, 130(4)

http://www.eurekalert.org/pub_releases/2001-12/apa-ocf121701.php

November 2001

Physical brain changes with advancing age

Many of the cognitive deficits associated with advancing age are related to functions of the prefrontal cortex such as working memory, decision-making, planning and judgement. Postmortem examination of 20 brains ranging in age from 25 to 83 years, confirm that prefrontal regions may be particularly sensitive to the effects of aging. It also appears that white matter decreases at a faster rate than grey matter with age.

Kigar, D.L., Walter, A.L., Stoner-Beresh, H.J. & Witelson, S.F. 2001. Age and volume of the human prefrontal cortex: a postmortem study. Paper presented to the annual Society for Neuroscience meeting in San Diego, US.

October 2001

Role of prefrontal cortical regions in goal-directed behaviour

Goal-directed behaviour depends on keeping relevant information in mind (working memory) and irrelevant information out of mind (behavioural inhibition or interference resolution). Prefrontal cortex is essential for both working memory and for interference resolution, but it is unknown whether these two mental abilities are mediated by common or distinct prefrontal regions. An imaging study found there was a high degree of overlap between the regions activated by load and interference, while no region was activated exclusively by interference. The findings suggest that, within the circuitry engaged by this task, some regions are more critically involved in the resolution of interference whereas others are more involved in the resolution of an increase in load.

Bunge, S.A., Ochsner, K.N., Desmond, J.E., Glover, G.H. & Gabrieli J.D.E. (2001). Prefrontal regions involved in keeping information in and out of mind. Brain, 124 (10), 2074-2086.

http://brain.oupjournals.org/cgi/content/abstract/124/10/2074

Left prefrontal cortex

January 2009

Switchboard in the brain helps us learn and remember at the same time

It’s very common that we are required to both process new information while simultaneously recalling old information, as in conversation we are paying attention to what the other person is saying while preparing our own reply. A new study confirms what has been theorised: that there is a bottleneck in our memory system preventing us from doing both simultaneously. Moreover, the study provides evidence that a specific region in the left prefrontal cortex can resolve the bottleneck, possibly by allowing rapid switching between learning and remembering. This is supported by earlier findings that patients with damage to this area have problems in rapidly adapting to new situations and tend to persevere in old rules. The same region is also affected in older adults.

Huijbers, W., Pennartz, C.M., Cabeza, R. & Daselaar, S.M. 2009. When learning and remembering compete: A functional MRI study. PLoS Biology, 7(1), e1000011. doi:10.1371/ journal.pbio.1000011

http://www.eurekalert.org/pub_releases/2009-01/plos-sit010909.php

January 2003

Learning a sequence with explicit knowledge of that sequence involves same

Imaging studies have found that sequence learning accompanied with awareness of the sequence activates entirely different brain regions than learning without awareness of the sequence. It has not been clear to what extent these two forms of learning (declarative vs procedural) are independent. A new imaging study devised a situation where subjects were simultaneously learning different sequences under implicit or explicit instructions, in order to establish whether, as many have thought, declarative learning prevents learning in procedural memory systems. It was found that procedural learning activated the left prefrontal cortex, left inferior parietal cortex, and right putamen. These same regions were also active during declarative learning. It appears that, in a well-controlled situation where procedural and declarative learning are occurring simultaneously, the same neural network for procedural learning is active whether that learning is or is not accompanied by declarative knowledge. Declarative learning, however, activates many additional brain regions.

Willingham, D.B., Salidis, J. & Gabrieli, J.D.E. 2003. Direct Comparison of Neural Systems Mediating Conscious and Unconscious Skill Learning. Journal of Neurophysiology, 88, 1451-1460.

November 2001

Differential effects of encoding strategy on brain activity patterns

Encoding and recognition of unfamiliar faces in young adults were examined using PET imaging to determine whether different encoding strategies would lead to differences in brain activity. It was found that encoding activated a primarily ventral system including bilateral temporal and fusiform regions and left prefrontal cortices, whereas recognition activated a primarily dorsal set of regions including right prefrontal and parietal areas. The type of encoding strategy produced different brain activity patterns. There was no effect of encoding strategy on brain activity during recognition. The left inferior prefrontal cortex was engaged during encoding regardless of strategy.

Bernstein, L.J., Beig, S., Siegenthaler, A.L. & Grady, C.L. 2002. The effect of encoding strategy on the neural correlates of memory for faces. Neuropsychologia, 40 (1), 86 - 98.

Medial prefrontal cortex

May 2009

Brain's problem-solving function at work when we daydream

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

February 2009

Brain hub links music and autobiographical memory

We all know that songs from our youth can evoke strong autobiographical memories. Now a new study explains why. Brain scans of students listening to excerpts of 30 different popular tunes found that a student recognized on average about 17 of the 30 excerpts, and of these, about 13 were moderately or strongly associated with an autobiographical memory. The strength of that memory was reflected in the amount of activity in the upper (dorsal) part of the medial prefrontal cortex, a region critically involved in integrating sensory information with self-knowledge and the retrieval of autobiographical information. Moreover, mapping the tones of each excerpt showed that the brain was tracking these tonal progressions in the same region as it was experiencing the memories: in the dorsal part of the medial prefrontal cortex, and the regions immediately adjacent to it. Again, the stronger the autobiographical memory, the greater the tracking activity. The finding explains why memory for autobiographically important music lingers in Alzheimer’s sufferers — the area is one of the last to be affected.

Janata, P. 2009. The Neural Architecture of Music-Evoked Autobiographical Memories. Cerebral Cortex, Advance Access published on February 24.

http://www.eurekalert.org/pub_releases/2009-02/uoc--sfb021809.php

May 2008

Brain region involved in false memories identified

We’re all susceptible to false memories, but brain damage can produce false memories beyond the normal level. The pathological production of false memories is known as confabulation, and because the patients who suffer this have showed damage to various parts of the brain, the cause has been unclear until now. But a new study of 50 patients has found the common element: all those who confabulated shared damage to the inferior medial prefrontal cortex.

Turner, M.S. et al. 2008. Confabulation: Damage to a specific inferior medial prefrontal system. Cortex, 44 (6), 637-648.

http://www.eurekalert.org/pub_releases/2008-05/e-wym052808.php

March 2007

Social memory localized

An imaging study has identified the medial prefrontal cortex as being the key structure in remembering social information (involving people and their interactions) from a picture. Previous studies have implicated this region with thinking about one’s self and others. This finding reveals that the region is involved not only in processing social information, but also storing it. The finding may help us understand disorders which affect social and relational skills, such as schizophrenia and autism.

Harvey, P.O., Fossati, P. & Lepage, M. 2007. Modulation of memory formation by stimulus content: specific role of the medial prefrontal cortex in the successful encoding of social pictures. Journal of Cognitive Neuroscience, 19, 351-362.

http://www.eurekalert.org/pub_releases/2007-03/c-tfo033007.php

May 2005

How the brain handles sarcasm

A study involving people with prefrontal lobe damage, people with posterior-lobe damage and healthy controls, found that those with prefrontal damage were impaired in comprehending sarcasm, whereas the people in the other two groups had no such problem. Within the prefrontal group, people with damage in the right ventromedial area had the most trouble in comprehending sarcasm. The researchers suggest that the frontal lobes process the context, identifying the contradiction between the literal meaning and the social/emotional context, while the ventromedial prefrontal cortex integrates the literal meaning with the social/emotional knowledge of the situation and previous situations.

Shamay-Tsoory, S.G., Tomer, R. & Aharon-Peretz, J. 2005. The Neuroanatomical Basis of Understanding Sarcasm and Its Relationship to Social Cognition. Neuropsychology, 19 (3)

http://www.eurekalert.org/pub_releases/2005-05/apa-tao051705.php

October 2004

Can't place a name to the face you just saw?

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

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

September 2009

Healthy older brains not significantly smaller than younger brains

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

Burgmans, S. et al. 2009. The Prevalence of Cortical Gray Matter Atrophy May Be Overestimated In the Healthy Aging Brain. Neuropsychology, 23 (5), 541-550.

http://www.eurekalert.org/pub_releases/2009-09/apa-hob090309.php

June 2009

Perception affected by mood

An imaging study has revealed that when people were shown a composite image with a face surrounded by "place" images, such as a house, and asked to identify the gender of the face, those in whom a bad mood had been induced didn’t process the places in the background. However, those in a good mood took in both the focal and background images. These differences in perception were coupled with differences in activity in the parahippocampal place area. Increasing the amount of information is of course not necessarily a good thing, as it may result in more distraction.

Schmitz, T.W., De Rosa, E. & Anderson, A.K. 2009. Opposing Influences of Affective State Valence on Visual Cortical Encoding. Journal of Neuroscience, 29 (22), 7199-7207.

http://www.eurekalert.org/pub_releases/2009-06/uot-pww060309.php

January 2006

Fitness counteracts cognitive decline from hormone-replacement therapy

A study of 54 postmenopausal women (aged 58 to 80) suggests that being physically fit offsets cognitive declines attributed to long-term hormone-replacement therapy. It was found that gray matter in four regions (left and right prefrontal cortex, left parahippocampal gyrus and left subgenual cortex) was progressively reduced with longer hormone treatment, with the decline beginning after more than 10 years of treatment. Therapy shorter than 10 years was associated with increased tissue volume. Higher fitness scores were also associated with greater tissue volume. Those undergoing long-term hormone therapy had more modest declines in tissue loss if their fitness level was high. Higher fitness levels were also associated with greater prefrontal white matter regions and in the genu of the corpus callosum. The findings need to be replicated with a larger sample, but are in line with animal studies finding that estrogen and exercise have similar effects: both stimulate brain-derived neurotrophic factor.

Erickson, K.I., Colcombe, S.J., Elavsky, S., McAuley, E., Korol, D., Scalf, P.E. & Kramer, A.F. 2006. Interactive effects of fitness and hormone treatment on brain health in postmenopausal women. Neurobiology of Aging, In Press, Corrected Proof, Available online 6 January 2006

http://www.eurekalert.org/pub_releases/2006-01/uoia-fcc012406.php

September 2003

More learned about how spatial navigation works in humans

Researchers monitored signals from individual brain cells as patients played a computer game in which they drove around a virtual town in a taxi, searching for passengers who appeared in random locations and delivering them to their destinations. Previous research has found specific cells in the brains of rodents that respond to “place”, but until now we haven’t known whether humans have such specific cells. This study identifies place cells (primarily found in the hippocampus), as well as “view” cells (responsive to landmarks; found mainly in the parahippocampal region) and “goal” cells (responsive to goals, found throughout the frontal and temporal lobes). Some cells respond to combinations of place, view and goal — for example, cells that responded to viewing an object only when that object was a goal.

Ekstrom, A.D., Kahana, M.J., Caplan, J.B., Fields, T.A., Isham, E.A., Newman, E.L. & Fried, I. 2003. Cellular networks underlying human spatial navigation.Nature, 425 (6954), 184-7.

http://www.eurekalert.org/pub_releases/2003-09/uoc--vgu091003.php

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

December 2009

Nerve-cell transplants help brain-damaged rats recover lost ability to learn

After destroying neurons in the subiculum of 48 adult rats, some were given hippocampal cells taken from newborn transgenic mice. On spatial memory tests two months later, the rats given cell transplants performed as well as rats which had not had their subiculums damaged; however, those without transplants had significantly impaired performance. The new cells were found to have mainly settled in the dentate gyrus, where they appeared to promote the secretion of two types of growth factors, namely BDNF and basic fibroblast growth factor (bFGF).

Rekha, J. et al. 2009. Transplantation of hippocampal cell lines restore spatial learning in rats with ventral subicular lesions. Behavioral Neuroscience, 123(6), 1197-1217.

http://www.eurekalert.org/pub_releases/2009-12/apa-nth120909.php

January 2009

Baby neurons time-stamp new memories

Since its discovery ten years, adult neurogenesis has been a fruitful area of research, but although we know it’s important for learning and memory, we’re still a little vague on how. Now a new computational model suggests that immature cells are very excitable, easily provoked into firing, while older neurons are more discriminating. The dentate gyrus is designed to separate new memories into separate events (pattern separation), but the indiscriminate excitability of newborn neurons means they link events and memories that happen around the same time (pattern integration) instead. As the brain cells mature, they settle down and join established neural circuits, taking on their proper role, but clusters of neurons that "grew up" around the same time still retain the memories forged in their youth. Which is why independent events that have nothing in common but the fact that they occurred at the same time are connected in our minds: baby neurons have ‘time-stamped’ them.

Aimone, J.B., Wiles, J. & Gage, F.H. 2009. Computational Influence of Adult Neurogenesis on Memory Encoding. Neuron, 61 (2), 187-202.

http://www.the-scientist.com/blog/display/55385/
http://www.eurekalert.org/pub_releases/2009-01/si-nbc012209.php

December 2008

Blood sugar linked to normal cognitive aging

Following research showing that decreasing brain function in the area of the hippocampus called the dentate gyrus is a main contributor of normal age-related cognitive decline, an imaging study has been investigating the cause of this decreasing function by looking at measures that typically change during aging, like rising blood sugar, body mass index, cholesterol and insulin levels. The study of 240 community-based nondemented elders (average age 80 years), of whom 60 had type 2 diabetes, found that decreasing activity in the dentate gyrus only correlated with levels of blood glucose. The same association was also found in aging rhesus monkeys and in mice. The finding suggests that maintaining blood sugar levels, even in the absence of diabetes, could help maintain aspects of cognitive health. It also suggests that one reason why physical exercise benefits memory may be its effect on lowering glucose levels.

Wu, W. et al. 2008. The brain in the age of old: The hippocampal formation is targeted differentially by diseases of late life. Annals of Neurology, 64 (6), 698-706.

http://www.eurekalert.org/pub_releases/2008-12/cumc-rac121508.php

August 2008

New brain cells are essential for learning

It was only a short time ago that it was accepted wisdom that new neurons were only created during childhood and that being an adult meant facing the gradual death, without replacement, of those neurons. Then, nearly a decade ago, it was discovered that adult brains could create new brain cells, albeit in a very limited way. However, it still hasn’t been clear how important adult neurogenesis is for learning and memory. Now a mouse study makes it clear that in one of the two regions in which neurogenesis takes place, it really is necessary. The study is the first to simultaneously study the two brain regions that produce new neurons, the subventricular zone and the dentate gyrus. Continual cell death was observed in the olfactory bulb, suggesting that newly born neurons (from the subventricular zone) are necessary to take their place. Neurons in the dentate gyrus, however, did not die regularly. However, when neurogenesis was knocked out in the olfactory bulb, no deficits occurred in smell memory, while the same action in the dentate gyrus did result in problems with spatial memory. The findings perhaps open up more questions than they answer — such as how odor memory is maintained when neurons in the olfactory bulb are being continuously replaced.

Imayoshi, I. et al. 2008. Roles of continuous neurogenesis in the structural and functional integrity of the adult forebrain.  Nature Neuroscience, Published online: 31 August 2008; doi:10.1038/nn.2185

http://www.the-scientist.com/blog/display/54993/
http://www.newscientist.com/channel/being-human/dn14630-new-brain-cells-are-essential-for-learning.html

February 2008

REM sleep deprivation reduces neurogenesis

And in another sleep study, rats deprived of REM sleep for four days showed reduced cell proliferation in the dentate gyrus of the hippocampus, where most adult neurogenesis takes place. The finding indicates that REM sleep is important for brain plasticity.

Guzman-Marin, R. et al. 2008. Rapid Eye Movement Sleep Deprivation Contributes to Reduction of Neurogenesis in the Hippocampal Dentate Gyrus of the Adult Rat. SLEEP, 31(2), 167-175.

http://www.eurekalert.org/pub_releases/2008-02/aaos-fdo012808.php

May 2007

Natural compound and exercise boost memory in mice

The flavanol epicatechin, found in blueberries, tea, grapes, and cocoa, has been found to enhance memory in mice. Moreover, this effect increased when mice also exercised regularly. The combination of exercise and a diet with epicatechin also promoted structural and functional changes in the dentate gyrus.

Praag, H. et al. 2007. Plant-Derived Flavanol (–)Epicatechin Enhances Angiogenesis and Retention of Spatial Memory in Mice. Journal of Neuroscience, 27, 5869-5878.

http://www.eurekalert.org/pub_releases/2007-05/sfn-nca052907.php

October 2005

Wnt signaling vital for adult neurogenesis

Neurogenesis (the birth of new neurons) only occurs in adult brains in two areas: the lateral ventricle, and the dentate gyrus (in the hippocampus). New neurons are spawned from the division of stem cells — but how do they decide whether to remain a stem cell, turn into a neuron, or a support cell (an astrocyte or oligodendrocyte)? A new study has pinpointed the protein that provides a vital chemical signal that helps this decision in the hippocampus. When Wnt3 proteins were blocked in the brains of adult mice, neurogenesis decreased dramatically; when additional Wnt3 was introduced, neurogenesis increased. Wnt3 molecules are secreted by astrocytes.

Lie, D-C., Colamarino, S.A., Song, H-J., Désiré, L., Mira, H., Consiglio, A., Lein, E.S., Jessberger, S., Lansford, H., Dearie, A.R. & Gage, F.H. 2005. Wnt signalling regulates adult hippocampal neurogenesis. Nature, 437, 1370-1375.

http://www.eurekalert.org/pub_releases/2005-10/si-wsc102405.php

July 2004

Social status influences brain structure

A rat study has found that dominant rats have more new nerve cells in the hippocampus than their subordinates, suggesting that social hierarchies can influence brain structure. Seven colonies of 6 rats (4 male and 2 female) established their pecking order within three days, and were tested two weeks later. The dominant males had some 30% more neurons in their dentate gyrus than both the subordinate rats and controls. The increase seems to be because the new cells constantly being born in this area of the brain (most of which usually die within a week) were surviving longer. Hippocampal neurons have already been shown to be responsive to negative factors such as stress, and positive factors such as exercise and environmental enrichment. The increase in neurons was maintained when the rats were removed from the social setting.

Kozorovitskiy, Y. & Gould, E.J. 2004. Dominance Hierarchy Influences Adult Neurogenesis in the Dentate Gyrus. The Journal of Neuroscience,24 (30), 6755-6759.

http://www.nature.com/news/2004/040802/full/040802-18.html

January 2003

More details about how memories are formed in the hippocampus

We know how important the hippocampus is in forming memories, but now, using newly developed imaging techniques, researchers have managed to observe how activity patterns within specific substructures of the hippocampus change during learning. The study identified areas within the hippocampus (the cornu ammonis and the dentate gyrus) as highly active during encoding of face-name pairs. This activity decreased as the associations were learned. A different area of the hippocampus (the subiculum) was active primarily during the retrieval of the face-name associations. Activity in the subiculum also decreased as retrieval became more practiced.

Zeineh, M.M., Engel, S.A., Thompson, P.M. & Bookheimer, S.Y. 2003. Dynamics of the Hippocampus During Encoding and Retrieval of Face-Name Pairs, Science, 299, 577-580.

http://www.eurekalert.org/pub_releases/2003-01/uoc--som012303.php

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

December 2009

The importance of retrieval cues

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

Cohn, M., Moscovitch, M., Lahat, A., & McAndrews, M. P. (2009). Recollection versus strength as the primary determinant of hippocampal engagement at retrieval. Proceedings of the National Academy of Sciences, 106(52), 22451-22455. doi: 10.1073/pnas.0908651106.

http://www.eurekalert.org/pub_releases/2009-12/uot-dik120709.php

Children’s PTSD symptoms linked to poor hippocampus function

An imaging study comparing brain activity during a verbal memory task of 16 10- to 17-year-olds who had PTSD symptoms with a control group of 11 young people, has found that while hippocampal activity was similar in both groups when the word list was presented, those with PTSD symptoms made more errors on the recall part of the test and showed less hippocampus activity than control subjects doing the same task. Additionally, those with the worst hippocampus function were also most likely to experience a specific set of PTSD symptoms — "avoidance and numbing", including difficulty remembering the trauma, feeling cut off from others and lack of emotion. The research helps explain why traumatized children behave as they do and could improve treatments.

Carrion, V. G., Haas, B. W., Garrett, A., Song, S., & Reiss, A. L. (2009). Reduced Hippocampal Activity in Youth with Posttraumatic Stress Symptoms: An fMRI Study. J. Pediatr. Psychol., jsp112. doi: 10.1093/jpepsy/jsp112.

http://www.eurekalert.org/pub_releases/2009-12/sumc-bis120309.php

Higher levels of leptin associated with lower risk of dementia

A new study has showed that higher levels of leptin—a hormone involved in fat metabolism and appetite—is linked to reduced risk of Alzheimer's disease. The study used data from the large long-running Framingham Heart Study, and found that higher leptin levels were not only associated with a dose-related lower incidence of dementia and Alzheimer’s, but also with higher total cerebral brain volume. The findings are consistent with recent evidence that leptin improves memory function through direct effects on the hippocampus. The strength of the association was striking (an Alzheimer’s risk of 25% for those with the lowest levels of leptin compared to 6% for those with the highest levels), and if confirmed will emphasize the role of lifestyle in preventing and treating Alzheimer’s.

Lieb, W., Beiser, A. S., Vasan, R. S., Tan, Z. S., Au, R., Harris, T. B., et al. (2009). Association of Plasma Leptin Levels With Incident Alzheimer Disease and MRI Measures of Brain Aging. JAMA, 302(23), 2565-2572. doi: 10.1001/jama.2009.1836.

http://www.eurekalert.org/pub_releases/2009-12/jaaj-hlo121009.php
http://www.eurekalert.org/pub_releases/2009-12/bumc-rfh121009.php

October 2009

High protein diet shrinks brain in Alzheimer’s mice

A study using genetically engineered mice has tested the effects of four diets for their effects on Alzheimer’s pathology: a regular diet, a high fat/low carbohydrate custom diet, a high protein/low carb version, or a high carbohydrate/low fat option. Unexpectedly, mice fed the high protein/low carbohydrate diet had brains 5% lighter that all the others, and regions of their hippocampus were less developed. Mice on the high fat diet had higher levels of amyloid-beta protein, although no effect on plaque burden was detected.

Franciosi, S., Gama Sosa, M., English, D., Oler, E., Oung, T., Janssen, W., et al. (2009). Novel cerebrovascular pathology in mice fed a high cholesterol diet. Molecular Neurodegeneration, 4(1), 42. doi: 10.1186/1750-1326-4-42.
Full text available at http://www.molecularneurodegeneration.com/content/4/1/40

http://www.eurekalert.org/pub_releases/2009-10/bc-arf101909.php

Why smells can be so memorable

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

The study appeared online on November 5 in Current Biology.

http://www.physorg.com/news176649240.html

Why sleep deprivation causes cognitive impairment, and how to fix it

A mouse study has found a molecular pathway in the brain that is the cause of cognitive impairment due to sleep deprivation, and points to a way of preventing the cognitive deficits caused by sleep deprivation. The study showed that mice deprived of sleep had increased levels of the enzyme phosphodiesterase 4 (PDE4) and reduced levels of cAMP, crucial in forming new synaptic connections in the hippocampus. Treatment with phosphodiesterase inhibitors rescued the sleep deprivation-induced deficits in cAMP signaling, synaptic plasticity and hippocampus-dependent memory, counteracting some of the memory consequences of sleep deprivation.

Vecsey, C. G., Baillie, G. S., Jaganath, D., Havekes, R., Daniels, A., Wimmer, M., et al. (2009). Sleep deprivation impairs cAMP signalling in the hippocampus. Nature, 461(7267), 1122-1125. doi: 10.1038/nature08488.

http://www.eurekalert.org/pub_releases/2009-10/uop-fsp102609.php

September 2009

Concepts are born in the hippocampus

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

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

http://www.newscientist.com/article/dn17862-concepts-are-born-in-the-hippocampus
http://www.eurekalert.org/pub_releases/2009-09/cp-hwk091709.php

How sleep consolidates memory

A rat study provides clear evidence that "sharp wave ripples", brainwaves that occur in the hippocampus when it is "off-line", most often during stage four sleep, are responsible for consolidating memory and transferring the learned information from the hippocampus to the neocortex, where long-term memories are stored. The study found that when these waves were eliminated during sleep, the rats were less able to remember a spatial navigation task.

Girardeau, G. et al. 2009. Selective suppression of hippocampal ripples impairs spatial memory. Nature Neuroscience, 12 (10), 1222-1223.

http://www.eurekalert.org/pub_releases/2009-09/ru-deo091509.php

New insights into memory without conscious awareness

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

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

http://www.eurekalert.org/pub_releases/2009-09/cp-ycb090309.php

Healthy older brains not significantly smaller than younger brains

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

Burgmans, S. et al. 2009. The Prevalence of Cortical Gray Matter Atrophy May Be Overestimated In the Healthy Aging Brain. Neuropsychology, 23 (5), 541-550.

http://www.eurekalert.org/pub_releases/2009-09/apa-hob090309.php

August 2009

Overweight and obese elderly have smaller brains

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

Alcoholics show abnormal brain activity when processing facial expressions

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

Memories practiced throughout the day, not just while sleeping

It is known that a certain amount of replaying of experiences occurs in the hippocampus immediately afterwards, but it has been thought that this is confined to the immediate past, while the replaying that occurs during sleep and is thought to be part of the memory consolidation process, ranges far more widely. Now a new rat study indicates that the replaying that occurs while the animal is awake is more extensive than thought, and more accurate than that which occurs during sleep. Data from the neurons indicated that the events being replayed (repeatedly) were from 20 to 30 minutes earlier, and involved different settings, indicating the replay wasn’t dependent on incoming sensory cues. It’s suggested that the less-accurate replays seen during sleep are more aimed at making connections, rather than consolidating the actual experience. The waking replays occurred during pauses in activity, perhaps suggesting the importance of making pauses for reflection during your day!

Karlsson, M.P. & Frank, L.M. 2009. Awake replay of remote experiences in the hippocampus. Nature Neuroscience, 12, 913–918.

http://www.eurekalert.org/pub_releases/2009-06/uoc--mmb061109.php

Measuring brain atrophy in patients with mild cognitive impairment

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

May 2009

New insight into how information is encoded in the hippocampus

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

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

http://www.eurekalert.org/pub_releases/2009-05/ciot-csr052909.php

Meditation may increase gray matter

Adding to the increasing evidence for the cognitive benefits of meditation, a new imaging study of 22 experienced meditators and 22 controls has revealed that meditators showed significantly larger volumes of the right hippocampus and the right orbitofrontal cortex, and to a lesser extent the right thalamus and the left inferior temporal gyrus. There were no regions where controls had significantly more gray matter than meditators. These areas of the brain are all closely linked to emotion, and may explain meditators' improved ability in regulating their emotions.

Luders, E. et al. 2009. The underlying anatomical correlates of long-term meditation: Larger hippocampal and frontal volumes of gray matter. NeuroImage, 45 (3), 672-678.

http://www.eurekalert.org/pub_releases/2009-05/uoc--htb051209.php

April 2009

Carriers of Alzheimer's gene show different brain activity as young adults

Possession of the ApoE4 gene variant associated with Alzheimer’s risk is found in about a quarter of the population, and has been shown to be associated with differences in the hippocampus in middle-aged and elderly healthy carriers. Now a new study of 36 younger adults (20-35) has revealed that differences in brain activity patterns between carriers and non-carriers are also evident at this stage, not only when performing a memory task, but even when the brain was at rest. Carriers of the gene had more brain activity in the hippocampus during the memory task, and more activity in the default mode network during rest. The findings support a theory that the brain's memory function may gradually wear itself out in those who go on to develop Alzheimer's.

Filippini, N. et al. 2009. Distinct patterns of brain activity in young carriers of the APOE-ε4 allele. Proceedings of the National Academy of Sciences, 106, 7209-7214.

http://www.eurekalert.org/pub_releases/2009-04/icl-yaa040609.php

How the brain translates memory into action

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

Bast, T. et al. 2009. From Rapid Place Learning to Behavioral Performance: A Key Role for the Intermediate Hippocampus. PLoS Biology, 7(4), e1000089. doi:10.1371/journal.pbio.1000089

http://www.eurekalert.org/pub_releases/2009-04/plos-nwd041709.php

March 2009

Shrinking in hippocampus precedes Alzheimer's

An imaging study of 64 Alzheimer's patients, 44 people with mild cognitive impairment, and 34 people with no memory or thinking problems, has found that those with smaller hippocampal volumes and higher rates of shrinkage were two to four times as likely to develop dementia over the study period (average 18 months) as those with larger volumes and a slower rate of atrophy. During that time, 23 of the people with MCI developed Alzheimer's, and three of the healthy participants.

Henneman, W.J.P. et al. 2009. Hippocampal atrophy rates in Alzheimer disease: Added value over whole brain volume measures. Neurology, 72, 999-1007.

http://www.eurekalert.org/pub_releases/2009-03/aaon-sih031009.php

February 2009

Physical fitness improves memory in seniors

A study of 165 older adults (59-81) has found a significant association between physical fitness and performance on certain spatial memory tests. Fitness was also strongly correlated with hippocampus size. Although rodent studies have shown that exercise increases hippocampus size and spatial memory, this is the first study to show that in humans. The findings provide more evidence for the benefits of physical exercise in preventing memory loss in older adults.

Erickson, K.I. et al.  2009. Aerobic fitness is associated with hippocampal volume in elderly humans. Hippocampus, Published online 2 January

http://www.eurekalert.org/pub_releases/2009-02/uoia-pfi022409.php

December 2008

Aging brains allow negative memories to fade

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

October 2008

Why it’s so hard to disrupt your routine

New research has added to our understanding of why we find it so hard to break a routine or overcome bad habits. The problem lies in the competition between the striatum and the hippocampus. The striatum is involved with habits and routines, for example, it records cues or landmarks that lead to a familiar destination. It’s the striatum that enables you to drive familiar routes without much conscious awareness. If you’re travelling an unfamiliar route however, you need the hippocampus, which is much ‘smarter’.  The mouse study found that when the striatum was disrupted, the mice had trouble navigating using landmarks, but they were actually better at spatial learning. When the hippocampus was disrupted, the converse was true. This may help us understand, and treat, certain mental illnesses in which patients have destructive, habit-like patterns of behavior or thought. Obsessive-compulsive disorder, Tourette syndrome, and drug addiction all involve abnormal function of the striatum. Cognitive-behavioral therapy may be thought of as trying to learn to use one of these systems to overcome and, ultimately, to re-train the other.

Lee, A.S. et al. 2008. A double dissociation revealing bidirectional competition between striatum and hippocampus during learning. Proceedings of the National Academy of Sciences, 105 (44), 17163-17168.

http://www.eurekalert.org/pub_releases/2008-10/yu-ce102008.php

Occasional memory loss tied to lower brain volume

A study of 503 seniors (aged 50-85) with no dementia found that 453 of them (90%) reported having occasional memory problems such as having trouble thinking of the right word or forgetting things that happened in the last day or two, or thinking problems such as having trouble concentrating or thinking more slowly than they used to. Such problems have been attributed to white matter lesions, which are very common in older adults, but all of the participants in the study had white matter lesions in their brains, and the amount of lesions was not tied to occasional memory problems. However it was found that those who reported having such problems had a smaller hippocampus than those who had no cognitive problems. This was most noteworthy in subjects with good objective cognitive performance.

van Norden, A.G.W. et al. 2008. Subjective cognitive failures and hippocampal volume in elderly with white matter lesions. Neurology, 71, 1152-1159.

http://www.eurekalert.org/pub_releases/2008-10/aaon-oml093008.php

Drinking alcohol associated with smaller brain volume

It is estimated that brain volume decreases by 1.9% per decade, accompanied by an increase in white matter lesions. Because moderate alcohol consumption has been associated with a lower risk of cardiovascular disease, it’s been thought that small amounts of alcohol might also reduce age-related declines in brain volume, although it’s known that large amounts of alcohol will reduce brain volume. However, a large, long-running study, has now found that, even at low levels of alcohol consumption, brain volume was negatively affected. Moreover, although men were more likely to be heavier drinkers, the association between drinking and brain volume was stronger in women.

Paul, C.A. et al. 2008. Association of Alcohol Consumption With Brain Volume in the Framingham Study. Archives of Neurology, 65(10), 1363-1367.

http://www.eurekalert.org/pub_releases/2008-10/jaaj-daa100908.php

August 2008

Encoding isn’t solely in the hippocampus

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

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

http://www.sciencedaily.com/releases/2008/08/080828220519.htm
http://www.eurekalert.org/pub_releases/2008-08/uoc--mts082808.php

June 2008

Long-term cannabis users may have structural brain abnormalities

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

How Ritalin works to focus attention

Ritalin has been widely used for decades to treat attention deficit hyperactivity disorder (ADHD), but until now the mechanism of how it works hasn’t been well understood. Now a rat study has found that Ritalin, in low doses, fine-tunes the functioning of neurons in the prefrontal cortex, and has little effect elsewhere in the brain. It appears that Ritalin dramatically increases the sensitivity of neurons in the prefrontal cortex to signals coming from the hippocampus. However, in higher doses, prefrontal neurons stopped responding to incoming information, impairing cognition. Low doses also reinforced coordinated activity of neurons, and weakened activity that wasn't well coordinated. All of this suggests that Ritalin strengthens dominant and important signals within the prefrontal cortex, while lessening weaker signals that may act as distractors.

Devilbiss, D.M.  & Berridge, C.W. 2008. Cognition-Enhancing Doses of Methylphenidate Preferentially Increase Prefrontal Cortex Neuronal Responsiveness. Biological Psychiatry, Available online 30 June 2008

http://www.eurekalert.org/pub_releases/2008-06/uow-suh062408.php

March 2008

Short-term stress can affect learning and memory

We know that long-lasting, severe stress can impair cell communication in the hippocampus. Now rodent studies have demonstrated that the same outcome can happen with short-term stress. But rather than involving the familiar stress hormone cortisol, acute stress activated corticotropin releasing hormones, which led to the rapid disintegration of dendritic spines in the hippocampus, thus limiting the ability of synapses to collect and store memories.

Chen, Y. et al. 2008. Rapid Loss of Dendritic Spines after Stress Involves Derangement of Spine Dynamics by Corticotropin-Releasing Hormone. Journal of Neuroscience, 28, 2903-2911.

http://www.eurekalert.org/pub_releases/2008-03/uoc--ssc031008.php

Injection of human umbilical cord blood helps aging brain

A rat study has found that a single intravenous injection of human umbilical cord blood mononuclear cells in aged rats significantly improved the microenvironment of the aged hippocampus and rejuvenated the aged neural stem/progenitor cells. The increase in neurogenesis seemed to be due to a decrease in inflammation. The results raise the possibility of cell therapy to rejuvenate the aged brain.

Bachstetter, A.D. et al. 2008. Peripheral injection of human umbilical cord blood stimulates neurogenesis in the aged rat brain. BMC Neuroscience, 9, 22.

http://www.physorg.com/news124384387.html

February 2008

Stress hormone impacts memory, learning in diabetic rodents

A rodent study sheds light on why diabetes can impair cognitive function. The study found that increased levels of a stress hormone (called cortisol in humans) in diabetic rats impaired synaptic plasticity and reduced neurogenesis in the hippocampus. When levels returned to normal, the hippocampus recovered. Cortisol production is controlled by the hypothalamic-pituitary axis (HPA). People with poorly controlled diabetes often have an overactive HPA axis and excessive cortisol.

Stranahan, A.M et al. 2008. Diabetes impairs hippocampal function through glucocorticoid-mediated effects on new and mature neurons. Nature Neuroscience, 11, 309–317.

http://www.eurekalert.org/pub_releases/2008-02/nioa-shi021508.php

October 2007

Mouse study points to new therapy for Fragile X sufferers

A mouse study has found evidence that fragile X mutation produces a highly selective impairment to long-term potentiation in hippocampal cells, and that adding brain-derived neurotrophic factor (BNDF) proteins to the hippocampus restored it.

Lauterborn, J.C. et al. 2007. Brain-Derived Neurotrophic Factor Rescues Synaptic Plasticity in a Mouse Model of Fragile X Syndrome. Journal of Neuroscience, 27 (40), 10685-10694.

http://www.eurekalert.org/pub_releases/2007-10/uoc--urr100507.php

Adult neurogenesis confirmed in primates

A study with marmosets has confirmed that the rate at which new neural cells form in the hippocampus (neurogenesis) begins to decline soon after reaching adulthood. This is the first study to confirm the finding from rodent studies in primates, and confirms that findings from rodent studies regarding ways of enhancing adult neurogenesis can be applied to primates.

Leuner, B., Kozorovitskiy, Y., Gross, C.G. & Gould, E. 2007. Diminished adult neurogenesis in the marmoset brain precedes old age. Proceedings of the National Academy of Sciences, 104 (43), 17169-17173.

http://www.eurekalert.org/pub_releases/2007-10/pu-bcg101207.php

March 2007

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

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

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

http://www.sciencedaily.com/releases/2007/03/070329092022.htm
http://www.eurekalert.org/pub_releases/2007-03/cumc-nrs032807.php

February 2007

Odor can help memory, in some circumstances

A study in which students played a computer version of a common memory game in which you turn over pairs of cards to find each one's match found that those who played in a rose-scented room and were later exposed to the same scent during slow-wave sleep, remembered the locations of the cards significantly better than people who didn't have that experience (97% vs 86%). Those exposed to the odor during REM sleep, however, saw no memory boost. Imaging revealed the hippocampus was activated when the odor was presented during slow-wave sleep. Having the smell available throughout sleep wouldn’t help, however, because we adapt to smells very quickly. Being exposed to the smell when being tested didn’t help either. Nor did experiencing the odor during slow-wave sleep help when the memory task involved a different type of memory — learning a finger-tapping sequence — probably because procedural memory doesn’t depend on the hippocampus.

Rasch, B., Büchel, C., Gais, S. & Born, J. 2007. Odor Cues During Slow-Wave Sleep Prompt Declarative Memory Consolidation. Science, 315 (5817), 1426-1429.

http://www.physorg.com/news92647884.html
http://www.nature.com/news/2007/070305/full/070305-10.html

January 2007

How we predict the future

A brain imaging study has revealed those regions involved in imagining future events are much the same as those regions involved in remembering past events, suggesting the brain apparently predicts the course of future events by imagining them taking place much like similar past ones. This is also consistent with observations from amnesic patients and very young children — that the capacity to predict the future depends on being able to remember the past. One set of regions that was more active while envisioning the future than while recollecting the past has been implicated in imagined (simulated) bodily movements, suggesting that we place future scenarios in well known visual–spatial contexts.

Szpunar, K.K., Watson, J.M. & McDermott, K.B. 2007. Neural substrates of envisioning the future. Proceedings of the National Academy of Sciences USA, 104, 642-647.

http://www.sciam.com/article.cfm?chanId=sa003&articleId=CFEBFD00-E7F2-99DF-3E7DCD24612A6C36
http://news.bbc.co.uk/2/hi/health/6216913.stm
http://www.sciencedaily.com/releases/2007/01/070102092224.htm

The finding is supported by another study, demonstrating that amnesic patients with primary damage to the hippocampus were markedly impaired at imagining new experiences in response to short verbal cues that outlined a range of simple commonplace scenarios. The patients were unable to visualize the whole experience in their mind's eye, seeing instead just a collection of separate images.

Hassabis, D., Kumaran, D., Vann, S.D. & Maguire, E.A. 2007. Patients with hippocampal amnesia cannot imagine new experiences. Proceedings of the National Academy of Sciences USA, 104 (5), 1726-1731.
Full text available at http://tinyurl.com/2jwpn3

http://www.eurekalert.org/pub_releases/2007-01/wt-pwa011107.php

Sleep deprivation affects neurogenesis

A rat study has found that rats deprived of sleep for 72 hours had higher levels of the stress hormone corticosterone, and produced significantly fewer new brain cells in a particular region of the hippocampus. Preventing corticosterone levels from rising also prevented the reduction in neurogenesis.

Mirescu, C., Peters, J.D., Noiman, L. & Gould, E. 2006. Sleep deprivation inhibits adult neurogenesis in the hippocampus by elevating glucocorticoids. Proceedings of the National Academy of Science, 103 (50), 19170-19175.

http://news.bbc.co.uk/2/hi/health/6347043.stm

December 2006

More on how memories are consolidated during sleep

A new study sheds more light on how memory is consolidated during sleep. Using a new technique, the research confirms that new information is transferred between the hippocampus and the cerebral cortex, and, unexpectedly, provides evidence suggesting that the cerebral cortex actively controls this transfer.

Hahn, T., Sakmann, B. & Mehta, M.R. 2006. Phase-locking of hippocampal interneurons' membrane potential to neocortical up-down states. Nature Neuroscience, 9, 1359-1361.

http://www.eurekalert.org/pub_releases/2006-12/m-lds120506.htm

Still more on how memories are consolidated during sleep

In research following up an earlier study in which rats were shown to form complex memories for sequences of events experienced while they were awake, and that these memories were replayed while they slept, it has been shown that these replayed memories do contain the visual images that were present during the running experience. By showing that the brain is replaying memory events in the visual cortex and in the hippocampus at the same time, the finding suggests that this process may contribute to or reflect the result of the memory consolidation process.

Ji, D. & Wilson, M.A. 2006. Coordinated memory replay in the visual cortex and hippocampus during sleep. Nature Neuroscience, 10, 100-107.

http://www.eurekalert.org/pub_releases/2006-12/miot-mtr121806.htm

Why neurogenesis is so much less in older brains

A rat study has revealed that the aging brain produces progressively fewer new nerve cells in the hippocampus (neurogenesis) not because there are fewer of the immature cells (neural stem cells) that can give rise to new neurons, but because they divide much less often. In young rats, around a quarter of the neural stem cells were actively dividing, but only 8% of cells in middle-aged rats and 4% in old rats were. This suggests a new approach to improving learning and memory function in the elderly.

Hattiangady, B. & Shetty, A.K. 2006. Aging does not alter the number or phenotype of putative stem/progenitor cells in the neurogenic region of the hippocampus. Neurobiology of Aging, In Press, Corrected Proof, Available online 7 November 2006.

http://www.eurekalert.org/pub_releases/2006-12/dumc-sca121806.htm

November 2006

Rote learning may improve verbal memory in seniors

A study involving 24 older adults (aged 55—70) has found that six weeks of intensive rote learning (memorizing a newspaper article or poem of 500 words every week) resulted in measurable changes in N-acetylaspartate, creatine and choline, three metabolites in the brain that are related to memory performance and neural cell health, in the left posterior hippocampus — but only after a six-week rest period, at which time the participants also showed improvements in their verbal and episodic memory, and also only in one of the two learning groups. The group that didn’t show any change were said to have low compliance with the memorization task.

McNulty, J. et al. The Identification of Neurometabolic Sequelae Post-learning Using Proton Magnetic Resonance Spectroscopy. Presented November 26 at the annual meeting of the Radiological Society of North America (RSNA).

http://www.eurekalert.org/pub_releases/2006-11/rson-rli112206.php

How the brain detects novelty

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

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

http://www.eurekalert.org/pub_releases/2006-11/wt-tot112406.php

October 2006

Repeated common infections may lead to memory deficits over a lifetime

A mouse study suggests that over the lifetime of an individual, a picornavirus-related infection could have a permanent effect on memory late in life. Picornaviruses are the most common infectious viral agents in humans. They include rhinoviruses, enteroviruses, encephalitis, myocarditis, meningitis, and those that cause foot-and-mouth disease, polio and hepatitis A. Generally individuals contract two or three enterovirus and/or rhinovirus infections each year. In the study, mice infected with an encephalomyelitis virus (comparable to the human poliovirus) had difficulty learning to navigate a maze designed to test various components of spatial memory. The degree of memory impairment was directly correlated to the number of dead brain cells in the hippocampus. "Our findings suggest that picornavirus infections throughout the lifetime of an individual may chip away at the cognitive reserve, increasing the likelihood of detectable cognitive impairment as the individual ages. We hypothesize that mild memory and cognitive impairments of unknown etiology may, in fact, be due to accumulative loss of hippocampus function caused by repeated infection with common and widespread neurovirulent picornaviruses."

Buenz, E.J., Rodriguez, M. & Howe, C.L. 2006. Disrupted spatial memory is a consequence of picornavirus infection. Neurobiology of Disease, 24 (2), 266-273.

http://www.eurekalert.org/pub_releases/2006-10/mc-mcs101706.php

'Memory gene' identified

Analysis of the human genome has revealed a gene associated with memory performance. The gene is called Kibra, and is expressed in the hippocampus. According to brain scans, people with the version of the gene related to poorer memory potential had to tax their brains harder to remember the same amount of information.

Papassotiropoulos, A. 2006. Common Kibra Alleles Are Associated with Human Memory Performance. Science, 314 (5798), 475-478.

http://www.eurekalert.org/pub_releases/2006-10/ttgr-rti101906.php

Why moderate drinking may boost memory

Another study has come out suggesting moderate amounts of alcohol are good for the brain, and explaining why. The rat study found that low levels of alcohol increased the expression of a particular receptor, NR1, on the surface of neurons in the hippocampus. Increasing the number of NR1 receptors in a different group of rats resulted in a memory boost similar to that seen in the rats given low doses of alcohol. There were no toxic effects of low-level alcohol consumption (1—2 drinks a day) on the brain, but a higher dose of alcohol did damage neurons.

The findings were presented at the Society for Neuroscience's annual meeting on October 14-18 in Atlanta, Georgia.

http://www.sciencedaily.com/releases/2006/10/061025171322.htm
http://www.eurekalert.org/pub_releases/2006-10/osu-mdm102506.php

Chemo drugs for treating breast cancer may cause changes in cognitive function

A study involving female mice confirms the existence of "chemobrain", finding mild to moderate learning and memory deficits in mice receiving methotrexate and 5-fluorouracil (5FU), two drugs widely used in women to prevent recurrence of breast cancer. The deficits extended only to those types of memory that involve the hippocampus or the frontal lobes (spatial memory and working memory, in this instance). The study only looked at short-term effects (2—4 weeks).

Winocur, G., Vardy, J., Binns, M.A., Kerr, L. & Tannock, I. 2006. The effects of the anti-cancer drugs, methotrexate and 5-fluorouracil, on cognitive function in mice. Pharmacology, Biochemistry and Behavior, 85 (1), 66-75.

http://www.eurekalert.org/pub_releases/2006-10/b-cdf102706.php

September 2006

Anticipation strengthens memory

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

August 2006

Childhood sleep apnea linked to brain damage, lower IQ

It’s long been known that sleep apnea, characterized by fragmented sleep, interrupted breathing and oxygen deprivation, harms children's learning ability and school performance. Now a new study involving 19 children with severe obstructive sleep apnea has identified damage in the hippocampus and the right frontal cortex, and linked that to observable deficits in performance on cognitive tests. Children with OSA had an average IQ of 85 compared to 101 in matched controls. They also performed worse on standardized tests measuring executive functions, such as verbal working memory (8 versus 15) and word fluency (9.7 versus 12). Obstructive sleep apnea affects 2% of children in the United States, but it is unclear how many of these suffer from severe apnea.

Springer, M.V., McIntosh, A.R., Winocur, G. & Grady, C.L. 2005. The Relation Between Brain Activity During Memory Tasks and Years of Education in Young and Older adults. Neuropsychology and Aging, 19 (2)

http://www.eurekalert.org/pub_releases/2006-08/jhmi-csa081506.php

February 2006

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

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

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

http://www.eurekalert.org/pub_releases/2006-02/uoc--urp020106.php

September 2005

Memory of fear more complex than supposed

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

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

How trauma triggers long-lasting memories in the brain

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

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

June 2005

How sleep improves memory

While previous research has been conflicting, it does now seem clear that sleep consolidates learning of motor skills in particular. A new imaging study involving 12 young adults taught a sequence of skilled finger movements has found a dramatic shift in activity pattern when doing the task in those who were allowed to sleep during the 12 hour period before testing. Increased activity was found in the right primary motor cortex, medial prefrontal lobe, hippocampus and left cerebellum — this is assumed to support faster and more accurate motor output. Decreased activity was found in the parietal cortices, the left insular cortex, temporal pole and fronto-polar region — these are assumed to reflect less anxiety and a reduced need for conscious spatial monitoring. It’s suggested that this is one reason why infants need so much sleep — motor skill learning is a high priority at this age. The findings may also have implications for stroke patients and others who have suffered brain injuries.

Walker, M.P., Stickgold, R., Alsop, D., Gaab, N. & Schlaug, G. 2005. Sleep-dependent motor memory plasticity in the human brain.Neuroscience, 133 (4) , 911-917.

http://www.eurekalert.org/pub_releases/2005-06/bidm-ssh062805.php

February 2005

Why traumatic memories have the power they do

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

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

May 2004

Hippocampus and subiculum both critical for short-term memory

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

Deadwyler, S.A. & Hampson, R.E. 2004. Differential but Complementary Mnemonic Functions of the Hippocampus and Subiculum. Neuron, 42 (3), 465-476.

http://www.eurekalert.org/pub_releases/2004-05/wfub-nrs050604.php

March 2004

Different brain regions for arousing and non-arousing words

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

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, selecting different aspects of the same stimulus image, most likely reflecting different histories, strategies, and expectations residing within individual hippocampal networks.

Hampson, R.E., Pons, T.P., Stanford, T.R. & Deadwyler, S.A. 2004. Categorization in the monkey hippocampus: A possible mechanism for encoding information into memory. PNAS, 101, 3184-3189. Published online before print as 10.1073/pnas.0400162101

http://www.eurekalert.org/pub_releases/2004-02/wfub-nfo022604.php

January 2004

Now definite? Memories are consolidated during sleep

Researchers of a new study claim that their research finally settles the question of whether or not sleep consolidates new memories. The study involved detailed recording of specific learning- and memory- related areas (hippocampus and forebrain) in the brains of rats. The rats were exposed to four kinds of novel objects. Analysis of brain signals before, during, and after this experience, revealed "reverberations" of distinctive brain wave patterns across all the areas being monitored for up to 48 hours after the novel experience. This pattern was much more prevalent in slow-wave sleep than in REM sleep. Previous studies by the same researchers have found that the activation of genes that affect memory consolidation occurs during REM sleep, not slow-wave sleep. It is proposed that both stages of sleep are important for memory consolidation. Previous studies have tended to focus solely on the hippocampus, and have observed brain activity for a much shorter period.

Ribeiro, S., Gervasoni, D., Soares, E.S., Zhou, Y., Lin, S-C., Pantoja, J., Lavine, M. & Nicolelis, M.A.L. 2004. Long-Lasting Novelty-Induced Neuronal Reverberation during Slow-Wave Sleep in Multiple Forebrain Areas. PLoS Biol 2(1): e24 DOI:10.1371/journal.pbio.0020024.

http://www.eurekalert.org/pub_releases/2004-01/dumc-etm011304.php
http://www.eurekalert.org/pub_releases/2004-01/plos-brd011204.php

Exercise may counteract bad effect of high-fat diet on memory

An animal study has investigated the interaction of diet and exercise on synaptic plasticity (an important factor in learning performance). A diet high in fat reduced levels of brain-derived neurotrophic factor (BDNF) in the hippocampus, and impaired performance on spatial learning tasks, but both of these consequences were prevented in those animals with access to voluntary wheel-running. Exercise appeared to interact with the same molecular systems disrupted by the high-fat diet.

Molteni, R., Wu, A., Vaynman, S., Ying, Z., Barnard, R.J. & Gómez-Pinilla, F. 2004. Exercise reverses the harmful effects of consumption of a high-fat diet on synaptic and behavioral plasticity associated to the action of brain-derived neurotrophic factor. Neuroscience, 123 (2), 429-440.

Forgetting may sometimes be an active process

New evidence suggests that forgetting may not simply be the passive phenomenon it has always been thought. Rather than simply a failure to properly encode or consolidate memories, forgetting may also be an active process — a deliberate action to erase unwanted memories. The recent study involved seeing the effect of a memory-blocking drug called APV on slices of brain tissue taken from the hippocampus of rats. APV blocks receptors for the neurotransmitter NMDA, which mediates the strengthening of synapses. While, as expected, NMDA activity was reduced in the treated hippocampal neurons, it was also found that “sharp waves” doubled in magnitude. This type of electrical activity is little understood, but it is known that such waves occur when an animal is alert but not actively exploring its environment or receiving sensory input, and they do not occur when brain activity associated with memory processing is occurring. Thus, the fact that a drug known to block memory, enhances sharp waves, is suggestive. The researchers speculate that sharp waves might work by reversing long-term potentiation — the mechanism by which synapses are thought to be strengthened — and that their function is to erase some of the information that was encoded during the active phase.

More evidence for active forgetting

In an imaging study involving 24 people aged 19 to 31, participants were given pairs of words and told to remember some of the matched pairs but forget others. Trying to shut out memory appeared more demanding than remembering, in that some areas of the brain were significantly more when trying to suppress memory. Both the prefrontal cortex and the hippocampus were active. Those whose prefrontal cortex and hippocampus were most active during this time were most successful at suppressing memory.

Anderson, M.C., Ochsner, K.N., Kuhl, B., Cooper, J., Robertson, E., Gabrieli, S.W., Glover, G.H. & Gabrieli, J.D.E. 2004. Neural Systems Underlying the Suppression of Unwanted Memories. Science, 303 (5655), 232-235.

http://www.eurekalert.org/pub_releases/2004-01/su-rrb010604.php

Gene essential for development of normal brain connections discovered

After birth, learning and experience change the architecture of the brain dramatically. The structure of individual neurons, or nerve cells, changes during learning to accommodate new connections between neurons. Neuroscientists believe these structural changes are initiated when neurons are activated, causing calcium ions to flow into cells and alter the activity of genes. Now the first gene, CREST, known to mediate these changes in the structure of neurons in response to calcium, has been discovered. In the study, it was found that mice lacking this gene didn’t develop normally in response to sensory experience, and their brains, while normal at birth, later showed far less interconnectivity between neurons. The gene produces a protein that, in adult humans, is produced in the hippocampus. It is therefore speculated that the protein may be necessary for learning and memory storage. The discovery of this gene may have implications for certain types of learning disorders in humans.

Aizawa, H., Hu, S-C., Bobb, K., Balakrishnan, K., Ince, G., Gurevich, I., Cowan, M. & Ghosh, A. 2004. Dendrite Development Regulated by CREST, a Calcium-Regulated Transcriptional Activator. Science, 303 (5655), 197-202.

http://www.eurekalert.org/pub_releases/2004-01/uoc--gef010804.php

Brain protein affecting learning and memory discovered

A significant new brain protein has been identified. Cypin is found throughout the body, but in the brain it now appears that it regulates neuron branching in the hippocampus. Such branching is thought to increase when learning occurs, and a reduction in branching is associated with certain neurological diseases. Discovery of this protein opens the possibility of new drug therapies for treating neurological disorders, and perhaps even memory-enhancing drugs.

Akum, B.F., Chen, M., Gunderson, S.I., Riefler, G.M., Scerri-Hansen, M.M. & Firestein, B.L. 2004. Cypin regulates dendrite patterning in hippocampal neurons by promoting microtubule assembly. Nature Neuroscience, 7(2), 145-152.

http://www.eurekalert.org/pub_releases/2004-01/rtsu-rsd011204.php
http://news.independent.co.uk/world/science_medical/story.jsp?story=482567

September 2003

More learned about how spatial navigation works in humans

Researchers monitored signals from individual brain cells as patients played a computer game in which they drove around a virtual town in a taxi, searching for passengers who appeared in random locations and delivering them to their destinations. Previous research has found specific cells in the brains of rodents that respond to “place”, but until now we haven’t known whether humans have such specific cells. This study identifies place cells (primarily found in the hippocampus), as well as “view” cells (responsive to landmarks; found mainly in the parahippocampal region) and “goal” cells (responsive to goals, found throughout the frontal and temporal lobes). Some cells respond to combinations of place, view and goal — for example, cells that responded to viewing an object only when that object was a goal.

Ekstrom, A.D., Kahana, M.J., Caplan, J.B., Fields, T.A., Isham, E.A., Newman, E.L. & Fried, I. 2003. Cellular networks underlying human spatial navigation.Nature, 425 (6954), 184-7.

http://www.eurekalert.org/pub_releases/2003-09/uoc--vgu091003.php

June 2003

Another step in understanding how memories are formed

The electrical activity of individual neurons in the brains of two adult rhesus monkeys was monitored while the monkeys played a memory-based video game in which an image pops up on the computer screen with four targets—white dots—superimposed on it. The monkeys’ task was to learn which target on which image was associated with a reward (a drop of their favorite fruit juice). Dramatic changes in the activity of some hippocampal neurons, which the scientists called "changing cells", paralleled their learning, indicating that these neurons are involved in the initial formation of new associative memories. In some of the cells, activity continued after the animal had learned the association, suggesting that these cells may participate in the eventual storage of the associations in long-term memory.

Wirth, S., Yanike, M., Frank, L.M., Smith, A.C., Brown, E.N. & Suzuki, W.A. 2003. Single Neurons in the Monkey Hippocampus and Learning of New Associations. Science, 300, 1578-1581.

http://www.eurekalert.org/pub_releases/2003-06/nyu-fir060503.php
http://tinyurl.com/ftob

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.php

February 2003

Another step in understanding how sleep affects memory

The value of sleep for memory takes a further step in being understood in new rodent research, which found that, as the rodents slept, the thalamus at the base of their brains originated bursts of electrical activity (“sleep spindles”), which were then detected in the somatosensory neocortex. Some 50 msec later, the hippocampus responded with a pulse of electricity (a “ripple”). "This neocortical-hippocampal dialogue may provide a selection mechanism for the time-compressed replay of information learned during the day." It’s suggested that the ripple is the hippocampus sending back neat, compact waves of memory to the neocortex where they are filed away for future reference. Most of this activity took place during slow wave sleep, the stage which makes up the majority of the sleep cycle.

Sirota, A., Csicsvari, J., Buhl, D. & Buzsáki, G. 2003. Communication between neocortex and hippocampus during sleep in rodents. Proc. Natl. Acad. Sci. USA, 100 (4), 2065-2069.

January 2003

Gene linked to poor episodic memory

Brain derived neurotrophic factor (BDNF) plays a key role in neuron growth and survival and, it now appears, memory. We inherit two copies of the BDNF gene - one from each parent - in either of two versions. Slightly more than a third inherit at least one copy of a version nicknamed "met," which the researchers have now linked to poorer memory. Those who inherit the “met” gene appear significantly worse at remembering events that have happened to them, probably as a result of the gene’s effect on hippocampal function. Most notably, those who had two copies of the “met” gene scored only 40% on a test of episodic (event) memory, while those who had two copies of the other version scored 70%. Other types of memory did not appear to be affected. It is speculated that having the “met” gene might also increase the risk of disorders such as Alzheimer’s and Parkinsons.

Egan, M.F., Kojima, M., Callicott, J.H., Goldberg, T.E., Kolachana, B.S., Bertolino, A., Zaitsev, E., Gold, B., Goldman, D., Dean, M., Lu, B. & Weinberger, D.R. 2003. The BDNF val66met Polymorphism Affects Activity-Dependent Secretion of BDNF and Human Memory and Hippocampal Function. Cell, 112, 257-269.

http://www.nih.gov/news/pr/jan2003/nimh-23.htm
http://www.eurekalert.org/pub_releases/2003-01/niom-hga012203.php
http://news.bbc.co.uk/1/hi/health/2687267.stm

More details about how memories are formed in the hippocampus

We know how important the hippocampus is in forming memories, but now, using newly developed imaging techniques, researchers have managed to observe how activity patterns within specific substructures of the hippocampus change during learning. The study identified areas within the hippocampus (the cornu ammonis and the dentate gyrus) as highly active during encoding of face-name pairs. This activity decreased as the associations were learned. A different area of the hippocampus (the subiculum) was active primarily during the retrieval of the face-name associations. Activity in the subiculum also decreased as retrieval became more practiced.

Zeineh, M.M., Engel, S.A., Thompson, P.M. & Bookheimer, S.Y. 2003. Dynamics of the Hippocampus During Encoding and Retrieval of Face-Name Pairs, Science, 299, 577-580.

http://www.eurekalert.org/pub_releases/2003-01/uoc--som012303.php

May 2002

Brain region involved in recalling memories from smell identified

We all know the power of smell in triggering the recall of memories. New research has found the specific area of the brain involved in this process - a section of the hippocampus called CA3. The hippocampus has long been known to play a crucial part in forming new memories. It appears that the CA3 region of the hippocampus is crucial for recalling memories from partial representations of the original stimulus.

Nakazawa, K., Quirk, M.C., Chitwood, R.A., Watanabe, M., Yeckel, M.F., Sun, L.D., Kato, A., Carr, C.A., Johnston, D., Wilson, M.A. & Tonegawa, S. 2002. Requirement for Hippocampal CA3 NMDA Receptors in Associative Memory Recall. Science 297, 211-218.

http://www.eurekalert.org/pub_releases/2002-05/bcom-tr052902.php
http://news.bbc.co.uk/hi/english/health/newsid_2017000/2017321.stm

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."

Fell, J., Klaver, P., Lehnertz, K., Grunwald, T., Schaller, C., Elger, C.E. & Fernández, G. 2001. Human memory formation is accompanied by rhinal-hippocampal coupling and decoupling. Nature Neuroscience 4(12), 1259-1264.

http://www.sciencenews.org/20011110/fob6.asp

New study contradicts earlier finding of new brain cell growth in the adult primate neocortex

A very exciting finding a couple of years ago, was that adult monkeys were found to be able to create new neurons in the neocortex, the most recently evolved part of the brain. However a new study, using the most sophisticated cell analysis techniques available to analyze thousands of cells in the neocortex, has found that those neurons that appear to be new are in fact two separate cells, usually one “old” neuron and one newly created cell of a different type, such as a glial cell — although new neurons were indeed found in the hippocampus and the olfactory bulb (both older parts of the brain).

Kornack, D.R. & Rakic, P. 2001. Cell Proliferation Without Neurogenesis in Adult Primate Neocortex. Science, 294 (5549), 2127-2130.

http://www.eurekalert.org/pub_releases/2001-12/uorm-std120601.php