News reports of research into memory January 2004

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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.
The researchers published their findings on Jan. 19, 2004, in the online Public Library of Science. Full reference
http://www.eurekalert.org/pub_releases/2004-01/dumc-etm011304.php
http://www.eurekalert.org/pub_releases/2004-01/plos-brd011204.php
http://www.plosbiology.org/plosonline/?request=get-document&doi=10.1371/journal.pbio.0020037
Full text: http://www.plosbiology.org/plosonline/?request=get-document&doi=10.1371%2Fjournal.pbio.0020024

Sleep helps insight

A new German study provides evidence for what we all suspected — “sleeping on” a problem can really work. In the study, participants were given a mathematical puzzle to solve; a puzzle which could be solved by trial-by-trial learning, or almost immediately if participants grasped the hidden rule. After training in the trial-by-trial learning, some of the participants were allowed to sleep through the night, while others were prevented from sleeping. When they returned to the problem eight hours later, those that had slept were twice as likely to realize the rule. Another group that trained in the morning, and were then tested later that day, were also slower at finding the rule, suggesting that the slowness was not solely due to fatigue. Sleep did not, however, help participants who had not had the initial training. It is suggested that sleep can act to restructure new memory representations.
The study was published on 22 January in Nature. Full reference
http://www.sciam.com/article.cfm?chanID=sa003&articleID=000088CE-E9DC-100E-A9DC83414B7F0000
http://www.sfgate.com/cgi-bin/article.cgi?file=/news/archive/2004/01/21/national0259EST0431.DTL
http://www.nature.com/nsu/040119/040119-10.html

Training improves working memory capacity

Working memory capacity has traditionally been thought to be constant. Recent studies, however, suggest that working memory can be improved by training. In this recent imaging study, it was found that adults who practiced working memory tasks for 5 weeks showed increased brain activity in the middle frontal gyrus and superior and inferior parietal cortices. These changes could be evidence of training-induced plasticity in the neural systems that underlie working memory.
The study was reported online on 14 December 2003 in Nature Neuroscience. Full reference
http://www.nature.com/cgi-taf/DynaPage.taf?file=/neuro/journal/v7/n1/abs/nn1165.html

International survey finds Ecstasy use affects long-term memory

An international web-based survey of Ecstasy users and non-drug users found that those who regularly took ecstasy suffered from mainly long-term memory difficulties, and that they were 23% more likely to report problems with remembering things than non-users (14% more likely compared to those who had never taken Ecstasy, but had taken other drugs). Those who regularly used cannabis reported up to 20% more memory problems than non-users, and their memory problems mainly involved short-term memory. The Ecstasy users also made 21% more errors on the questionnaire form than non-ecstasy users and 29% more mistakes than people who did not take drugs at all. The study involved 763 people, from which 81 'typical' ecstasy users who had taken the drug at least ten times were selected for closer investigation. There were no significant differences between genders.
Results of the study are published in the December edition of the Journal of Psychopharmacology. Full reference
http://www.eurekalert.org/pub_releases/2004-01/uonu-eam011304.php

Risk for lowered cognitive performance greater in people at high risk for stroke

A new large-scale study supports earlier suggestions that those with a high risk for stroke within 10 years are also at risk for lowered cognitive function and show a pattern of deficits similar to that seen in mild vascular cognitive impairment. It is speculated that the reason may lie in structural and functional changes in the brain that do not rise to the level of clinical detection, and this is supported by a recent brain imaging study showing that abnormal brain atrophy is related both to higher risk of stroke and poorer cognitive ability. The probability of experiencing stroke within 10 years was calculated using weighted combinations of age, systolic blood-pressure, presence of diabetes, cigarette smoking, history of cardiovascular disease, treatment for hypertension and atrial fibrillation.
Thefindings were published in the February issue of Stroke, and online before print on January 15. Full reference
http://www.eurekalert.org/pub_releases/2004-01/ama-rfl010804.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.
The study appeared in Neuroscience. Full reference
http://journals.bmn.com/jsearch/search/record?uid=NSC.bmn09190_03064522_v0123i02_03007425&rendertype=abstract

Knowledge-based IQ test predicts work performance as well as school

A meta-analysis of 127 studies supports the view that the Miller Analogies Test (MAT) — a knowledge-based test used for admissions decisions into U.S. graduate schools as well as in hiring and promotion decisions in the workplace since 1926 — is predictive of performance in both the academic and workplace environments. Specifically, MAT was a valid predictor of seven of the eight measures of graduate student performance, five of the six school-to-work transition performance criteria, and all four of the work performance criteria. MAT is assumed to measure “g”, the oft-debated “general intelligence” factor.
The study was published in the January issue of the Journal of Personality and Social Psychology. Full reference
Full text available at http://www.apa.org/journals/psp/press_releases/january_2004/psp861148.pdf
http://www.apa.org/releases/success.html

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. http://gateways.bmn.com/neuroscience/news?uid=NEWS.040114-1

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.
The study appeared in the January 9 issue of Science. Full reference
http://www.eurekalert.org/pub_releases/2004-01/su-rrb010604.php

Gene may be key to evolution of larger human brain

Researchers have now identified a gene that appears to have played a significant role in the expansion of the human brain's cerebral cortex. The gene is called the Abnormal Spindle-Like Microcephaly Associated (ASPM) gene, and dysfunction in this gene is linked to human microcephaly — a severe reduction in the size of the cerebral cortex. Comparison of the gene sequence in humans with that of 6 other primates (progressively less related to humans) revealed that the ASPM gene showed clear evidence of changes accelerated by evolutionary pressure in the lineage leading to humans, and the acceleration was most prominent in recent human evolution after humans diverged from chimpanzees (our closest primate relative) some five million years ago. A massive population-wide genetic change in the gene seems to have occurred in the human lineage every 300,000 to 400,000 years since then, with the last such change occurring between 200,000 and 500,000 years ago. Such strong evidence of evolutionary change is most unusual. No such change was found when other (non-primate) mammals were investigated.
An advance access article was published on January 13, in Human Molecular Genetics. Full reference
http://www.eurekalert.org/pub_releases/2004-01/hhmi-gmb011204.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.
The paper featured on the cover of the January 9 issue of Science. Full reference
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.
The paper was published online 18 January, and appeared in the February issue of Nature Neuroscience. Full reference
http://www.eurekalert.org/pub_releases/2004-01/rtsu-rsd011204.php
http://news.independent.co.uk/world/science_medical/story.jsp?story=482567

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