News reports of research into memory August 2008

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August 2008

Decline of mental skills in years before death

A long-running study of 288 people with no dementia, who were followed from age 70 to death, has found that there was substantialacceleration in cognitive decline many years prior to death. Time of onset and rate of terminal decline varied considerably across cognitive abilities, with verbal ability beginning its terminal decline 6.6 years prior to death, spatial ability 7.8 years before death, and perceptual speed 14.8 years before death. With verbal ability, it appeared that the decline was not due to age only, but due to health issues.
The study is published in the August 27 issue of Neurology. Full reference
http://www.eurekalert.org/pub_releases/2008-08/aaon-ewd081908.php

Pre-school exercises can prevent dyslexia

A study comparing 107 children with either parent dyslexic and a control group of children without a hereditary predisposition to dyslexia has found that half the children with a dyslexic parent found learning to read more challenging than children in the control group. The predictors of reading and writing difficulties were evident primarily in two contexts: as a delayed ability to perceive and mentally process the subtleties of speech sound, and as a sluggishness in naming familiar, visually presented objects. The difficulties children experience when learning to read can be significantly reduced through training, and the CoE in Learning and Motivation Research has developed computer game-like learning environments to aid preventive training, and made them available on the internet free of charge. It’s recommended that the child start these exercises before school, if possible. The exercises and tools are all available at www.lukimat.fi.
The results were presented at the Academy of Finland's science breakfast on 21 August.
http://www.eurekalert.org/pub_releases/2008-08/aof-pae082708.php

Why it's hard to hear in a crowded room

New research helps explain why it’s difficult for those with impaired hearing to hear conversation involving several different people, particularly in a busy setting such as a restaurant or at a party. It appears that as you attend to a continuous auditory stream (such as one person speaking from one location), your attention gets refined and improved over time. However, if that person gets changing location, or if you have to focus on more than one speaker, then degradation occurs as attention gets switched and begins the process of building up performance again. It’s speculated that the same sort of attentional selectivity may occur with objects in a complex visual scene (think of “Where’s Wally”).
The findings were published online August 21 in the Proceedings of the National Academy of Sciences. Full reference
http://www.eurekalert.org/pub_releases/2008-08/bu-mta082108.php

One sleepless night increases dopamine

A study has found that sleep deprivation increases the level of the hormone dopamine in two brain structures: the striatum, which is involved in motivation and reward, and the thalamus, which is involved in alertness. The rise in dopamine following sleep deprivation may promote wakefulness to compensate for sleep loss. However, since the amount of dopamine correlated with feelings of fatigue and impaired performance on cognitive tasks, it appears that the adaptation is not sufficient to overcome the cognitive deterioration induced by sleep deprivation and may even contribute to it. Amphetamines increase dopamine levels.
The research appeared in the August 20 issue of The Journal of Neuroscience. Full reference
http://www.eurekalert.org/pub_releases/2008-08/sfn-osn081808.php

Sleep selectively preserves emotional memories

It’s now generally accepted that sleep plays an important role in consolidating procedural (skill) memories, but the position regarding other types of memory has been less clear. A new study has found that sleep had an effect on emotional aspects of a memory. The study involved showing 88 students neutral scenes (such as a car parked on a street in front of shops) or negative scenes (a badly crashed car parked on a similar street). They were then tested for their memories of both the central objects in the pictures and the backgrounds in the scenes, either after 12 daytime hours, or 12 night-time hours, or 30 minutes after viewing the images, in either the morning or evening. Those tested after 12 daytime hours largely forgot the entire negative scene, forgetting both the central objects and the backgrounds equally. But those tested after a night’s sleep remembered the emotional item (e.g., the smashed car) as well as those who were tested only 30 minutes later. Their memory of the neutral background was however, as bad as the daytime group. The findings are consistent with the view that the individual components of emotional memory become 'unbound' during sleep, enabling the brain to selectively preserve only that information it considers important.
The study was reported in the August issue of Psychological Science. Full reference
http://www.physorg.com/news137908693.html
http://www.eurekalert.org/pub_releases/2008-08/bidm-sft081308.php

Hot flashes underreported and linked to forgetfulness

In the first study to explore the relationship between objectively measured hot flashes in menopausal women and memory performance, it’s been found that women dramatically underreport the number of hot flashes they experience (by about 43%), and that, with a clear measure of hot flashes, an association between number of hot flashes and poor verbal memory is evident. There was no relationship between the number of hot flashes women thought they had and memory performance. The average number of objective hot flashes was 19.5 per day. Unsurprisingly, poor sleep also predicted poorer memory, but it was also affected by the number of hot flashes during the night when a woman was sleeping. The researchers recommend treating women for their vasomotor symptoms.
An extended interview as MP3 audio file is at https://blackboard.uic.edu/bbcswebdav/institution/web/news/podcasts/PdCst47-June16%2708-Maki.mp3
The study is published online and will appear in the September/October issue of Menopause. Full reference
http://www.eurekalert.org/pub_releases/2008-06/uoia-hfu061608.php

B-vitamin deficiency may cause vascular cognitive impairment

A new mouse study helps clarify the association between homocysteine, folate & B12, and cognitive impairment. The study found that mice fed a diet deficient in folate and vitamins B12 and B6 demonstrated significant deficits in spatial learning and memory compared with normal mice, developed plasma homocysteine concentrations that were seven-fold higher, and showed smaller capillary length and density in blood vessels in the hippocampus. Homocysteine is produced by the breakdown of a dietary protein called methionine; B-vitamins are required to convert homocysteine back to methionine. A third group of mice were fed a diet enriched with methionine. These mice showed similar, but less pronounced effects. The findings indicate that increased levels of homocysteine, produced by low intake of folate and B vitamins, impairs cognition through microvascular changes.
The findings appeared in the August 26 issue of Proceedings of the National Academy of Sciences. Full reference
Full text is available at http://www.pnas.org/content/105/34/12474.abstract
http://www.physorg.com/news139574626.html

Eating fish may prevent memory loss and stroke in old age

A large study involving 3,660 people age 65 and older over five years, has found that those who ate broiled or baked tuna and other fish high in omega-3 fatty acids three times or more per week had a nearly 26% lower risk of having silent brain infarcts that can cause dementia and stroke, compared to people who did not eat fish regularly. One serving a week reduced risk by 13%. Regular fish consumption was also associated with fewer changes in white matter. Types of fish that contain high levels of DHA and EPA nutrients include salmon, mackerel, herring, sardines, and anchovies. Eating fried fish was not protective. Silent brain infarcts are only detected by brain scans, and are found in about 20% of otherwise healthy elderly people.

However, in the same journal, another study reports findings that in a double-blind, placebo-controlled, study of 302 healthy older adults, 26 weeks of EPA-DHA supplements had no effect on cognitive performance. Of course, if the effect of fish oil is primarily on preserving brain health, it may well be (indeed is likely) that the study was too short to impact cognitive performance. It is also possible that supplements are not as effective as whole foods — many studies have found that it is much more effective to receive needed vitamins and minerals through nutrition rather than supplementation. Reference

The studies were published in the August 5 issue of Neurology. Full reference
http://www.eurekalert.org/pub_releases/2008-08/aaon-efm072908.php

Feed TBI patients early and well

Analysis of the results of 797 comatose brain trauma patients treated at 21 trauma centers in New York over six years has found that patients who did not get fed within five or seven days were two-fold and four-fold more likely to die in the two week period following initial trauma. The amount of nutrition in the first 5 days was related to death; every 10-kcal/kg decrease in caloric intake was associated with a 30–40% increase in mortality rates. The findings overturn current guidelines for TBI patient care, pointing to the importance of aggressive early nutrition.
The report appeared in the July issue of the Journal of Neurosurgery. Full reference
http://www.sciencentral.com/articles/view.php3?article_id=218393144

A new perspective on forgetting

A new mathematical model may shed light on forgetting. The model has found that "free-lunch learning" (the way in which forgotten material is called back to mind when we relearn some part of it — as when a few words in a foreign language we learned at school brings back many other words) occurs when forgetting was induced by random fluctuations in the strength of synaptic connections (‘synaptic drift'). But when forgetting is induced by progressive decay in synaptic strength (which is how forgetting has traditionally been thought of), then "negative free-lunch learning" (where relearning parts of forgotten associations decreases the recall of associated knowledge) occurs. This suggests that forgetting occurs because of random drift rather than a decay in the strength of synaptic connections.
Details were published August 22 in the open-access journal PLoS Computational Biology. Full reference
Full text available at http://dx.plos.org/10.1371/journal.pcbi.1000143
http://www.eurekalert.org/pub_releases/2008-08/plos-rpn082108.php

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.
The study appeared online August 31 in Nature Neuroscience. Full reference
http://www.the-scientist.com/blog/display/54993/
http://www.newscientist.com/channel/being-human/dn14630-new-brain-cells-are-essential-for-learning.html

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.
The research was published in the August 28 issue of Neuron. Full reference
http://www.sciencedaily.com/releases/2008/08/080828220519.htm
http://www.eurekalert.org/pub_releases/2008-08/uoc--mts082808.php