News reports of research into memory September 2005

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September 2005

Memory loss in older adults due to distractions, not inability to focus

We know that older adults often have short-term memory problems, and this has been linked to problems with attention. An imaging study now provides evidence that these short-term memory problems are associated with an inability to filter out surrounding distractions, rather than problems with focusing attention. It’s been suggested that an inability to ignore distracting information may indeed be at the heart of many of the cognitive problems that accompany aging. It should be noted that this is not an inevitable effect of age — in the study, 6 of the 16 older adults involved had no problems with short-term memory or attention.
The report appeared online on September 11 in Nature Neuroscience. Full reference
http://www.eurekalert.org/pub_releases/2005-09/uoc--mli090805.php

More evidence for value of folate for aging brains

Confirming a growing body of evidence, a study of 50-85 year old Boston-area men (members of the ongoing Normative Aging Study) found that men who obtained more folate in their diets showed significantly less of a decline in verbal fluency skills over the course of three years than did men with lower dietary folate intake. High folate levels also appeared protective against declines in spatial copying. The effects of folate were independent of its impact on homocysteine, which turned out to be more strongly associated with tests of memory. Folate is a B vitamin found particularly in leafy green vegetables and citrus fruit.
The study was reported in the American Journal of Clinical Nutrition. Full reference
http://www.eurekalert.org/pub_releases/2005-09/tu-lgv092205.php

Preventing high levels of homocysteine may protect against age-related cognitive impairment

Previous studies have found a link between high levels of homocysteine and poor cognitive performance, but it has been difficult to work out just what the association is, in view of confounding factors such as cardiovascular risk factors and levels of folate, B12, and B6, all of which play a role in high levels of homocysteine. A new analysis has disentangled these factors, and has found that, in people over 60 (but not those under 60), higher levels of homocysteine are independently associated with lower levels of cognitive performance. Similarly, higher levels of vitamin B12 are associated with higher levels of cognitive performance. The researchers suggest vitamins B12, B6, and folate taken before 60 could help protect against later cognitive impairment.
The report appeared in the August 17 issue of the American Journal of Epidemiology. Full reference
http://www.eurekalert.org/pub_releases/2005-09/bu-atp092705.php

High blood pressure has stronger effect on cognitive function in African-Americans

Analysis of a large longitudinal study (the Maine-Syracuse Longitudinal Study 1976—2002) has found significant associations of high blood pressure to lower cognitive performance in the areas of abstract reasoning, psychomotor skills and visual organization skills. This association, moreover, was significantly greater for African-Americans, although it should be noted that there were only 147 African-Americans among the 1,563 participants. The effect was independent of age.
The report appeared in the September/October issue of Psychosomatic Medicine. Full reference
http://www.eurekalert.org/pub_releases/2005-09/cfta-hbp092205.php

Smoking seems to increase brain damage in alcoholics

Another study has come out indicating that alcoholics who smoke are at greater risk of brain damage. The imaging study compared brain volume in recovered alcoholics and light drinkers. The study found no difference between smokers and non-smokers among the light drinkers, but among the alcoholics, the more severe the tobacco habit, the more brain volume had been lost.
The study was published in the August issue of Alcoholism: Clinical and Experimental Research. Full reference
http://www.eurekalert.org/pub_releases/2005-09/uoc--sst092805.php

Key neural system at risk from fetal alcohol exposure

A study of pregnant rhesus monkeys has found that prenatal exposure to alcohol has pronounced effects on the development and function later in life of the brain's dopamine system. Dopamine is a key chemical messenger in the brain. The study indicates there is no safe dose, nor safe time to drink, for pregnant women. The monkeys consumed the equivalent of one to two drinks a day. Abnormalities in dopamine functioning can contribute to addiction, memory, attention and problem solving, and more pronounced conditions such as schizophrenia. The nature of the damage is significantly different depending on the timing of the alcohol exposure.
The report appeared in the September 15 issue of Alcoholism: Clinical and Experimental Research. Full reference
http://www.eurekalert.org/pub_releases/2005-09/uow-kns091305.php

Prenatal exposure to marine toxin causes lasting damage

A rat study has found that a single dose of the naturally occurring marine toxin domoic acid caused subtle but permanent cognitive damage in rats exposed to the chemical before birth. The effect occurred at levels below those generally deemed safe, and suggest that the toxin might negatively affect unborn children at levels that do not cause symptoms in expectant mothers. It was already known that toxic doses of domoic acid can damage the hippocampus.
The findings will appear in a forthcoming special issue of Neurotoxicology and Teratology. Full reference
http://www.eurekalert.org/pub_releases/2005-09/dumc-pet090605.php

A friendly reminder for HIV patients

Treating HIV requires patients to rigorously follow a medication schedule; more than most diseases, the virus easily develops a resistance to the drugs if not taken reliably. Moreover, HIV can cause brain damage, making it more difficult for some patients to remember. A device known as Jerry (more formally, the Disease Management Assistance System) flashes a light and verbally tells the patient the exact dosage and medication to take at the correct time. Of the 58 patients in a recent study, those with Jerry took their medication 80% of the time, while those without did so only 65% of the time. The difference was only significant for those with memory impairment: of the 31 memory-impaired patients, those using Jerry had a 77% adherence rate, while those without Jerry had a 57% adherence rate.
The study was published in the September 15 issue of Clinical Infectious Diseases. Full reference
http://www.journals.uchicago.edu/CID/journal/rapid.html
http://www.eurekalert.org/pub_releases/2005-09/jhmi-afr091305.php

Concrete evidence of the 'memory code'

I’m always talking about the “memory code”, and its existence is central to theories of memory, but now, for the first time, researchers have found concrete evidence of it. The coding system was discovered during an investigation into how the primary auditory cortex responds to different sounds. Rats were trained with various tones; it was found that the more important the tone, the greater the area of auditory cortex that became tuned to it — in other words, more neurons were involved in storing the information.
The study was reported in the September 20 issue of the Proceedings of the National Academy of Sciences. Full reference
Full text is available at: http://tinyurl.com/crnbl
http://www.eurekalert.org/pub_releases/2005-09/uoc--unu090805.php

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.
The paper was published in the September15 issue of Neuron. Full reference
http://www.eurekalert.org/pub_releases/2005-09/uot-sco091505.php

Human brains still evolving

Two genes active in the brain — Microcephalin and ASPM — have now been sequenced. Both regulate brain size. The sequencing has revealed a distinctive mutation in both genes, both of which change the protein the gene codes for. For the Microcephalin gene, the mutation is now in the brains of about 70% of humans, and half of this group carry completely identical versions of the gene, suggesting the mutation arose recently (between 60,000 and 14,000 years ago) and spread quickly through the human species due to selection pressure, rather than accumulating random changes through neutral genetic drift. The new variant of ASPM appeared in humans even more recently — somewhere between 14,000 and 500 years ago — and is already present in about a quarter of people alive today.
The reports appeared in the September 9 issue of Science. Full reference 2
http://www.newscientist.com/article.ns?id=dn7974
http://www.sciencentral.com/articles/view.htm3?article_id=218392658