News reports of research into memory April 2004

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April 2004

Even moderate iron deficiency affects cognitive performance

A new study involving 149 young women (aged 18 to 35, average age 21), has found that iron supplementation significantly improved attention, short-term and long-term memory, and performance on cognitive tasks in those who were deficient in iron, even if not classified as anemic. On the baseline test, women who were iron deficient but not anemic completed the tasks in the same amount of time as iron sufficient women of the same age, but they performed significantly worse. Women who were anemic both performed significantly worse and took longer, with length of time increasing with degree of anemia. However, 16 weeks of iron supplementation markedly improved both scores and time to complete the task.
While iron deficiency was once presumed to exert most of its deleterious effects only if it had reached the level of anemia, it has more recently become recognized that many organs show negative changes in functioning before there is any drop in iron hemoglobin concentration. Iron deficiency is thought to occur in 9 – 11% of women of reproductive age and 25% of pregnant women. In non-industrialized countries, the prevalence of anemia is over 40% in non-pregnant women and over 50% for pregnant women and children aged five to 14.
The study was presented at Experimental Biology 2004, in the American Society of Nutritional Sciences' scientific program. Reference
http://www.eurekalert.org/pub_releases/2004-04/foas-mid040404.php

How we retrieve distant memories

We know that recent memories are stored in the hippocampus, but these memories do not remain there forever. It has been less clear how we retrieve much older memories. Now studies of mice genetically altered to be unable to recall old memories have demonstrated that a part of the cortex called the anterior cingulate is critical for this process. It is suggested that, rather than this structure being the storage site for old memories, the anterior cingulate assembles signals of an old memory from different sites in the brain. Dementia may result from a malfunction in this assembling process, leaving the memory too fragmented to make proper sense. Both ageing and certain aspects of Alzheimer's disease and other dementias are all accompanied by reduced activity in the anterior cingulate.
The work was published in the May 7 issue of Science. Full reference
http://news.bbc.co.uk/2/hi/health/3689335.stm

Why working memory capacity is so limited

There’s an old parlor game whereby someone brings into a room a tray covered with a number of different small objects, which they show to the people in the room for one minute, before whisking it away again. The participants are then required to write down as many objects as they can remember. For those who perform badly at this type of thing, some consolation from researchers: it’s not (entirely) your fault. We do actually have a very limited storage capacity for visual short-term memory.
Now visual short-term memory is of course vital for a number of functions, and reflecting this, there is an extensive network of brain structures supporting this type of memory. However, a new imaging study suggests that the limited storage capacity is due mainly to just one of these regions: the posterior parietal cortex. An interesting distinction can be made here between registering information and actually “holding it in mind”. Activity in the posterior parietal cortex strongly correlated with the number of objects the subjects were able to remember, but only if the participants were asked to remember. In contrast, regions of the visual cortex in the occipital lobe responded differently to the number of objects even when participants were not asked to remember what they had seen.
The research was published in the April 15 edition of Nature. Full reference
http://www.eurekalert.org/pub_releases/2004-04/vu-slo040704.php
http://tinyurl.com/2jzwe (Telegraph article)

Brain signal predicts working memory capacity

Our visual short-term memory may have an extremely limited capacity, but some people do have a greater capacity than others. A new study reveals that an individual's capacity for such visual working memory can be predicted by his or her brainwaves. In the study, participants briefly viewed a picture containing colored squares, followed by a one-second delay, and then a test picture. They pressed buttons to indicate whether the test picture was identical to -- or differed by one color -- from the one seen earlier. The more squares a subject could correctly identify having just seen, the greater his/her visual working memory capacity, and the higher the spike of corresponding brain activity – up to a point. Neural activity of subjects with poorer working memory scores leveled off early, showing little or no increase when the number of squares to remember increased from 2 to 4, while those with high capacity showed large increases. Subjects averaged 2.8 squares.
The study appeared in the April 15 issue of Nature. Full reference
http://www.eurekalert.org/pub_releases/2004-04/niom-bsp041604.php
http://tinyurl.com/2jzwe (Telegraph article)

Brain region involved in insight localized

An imaging study has revealed a unique neural signature of those “Aha!” moments of sudden insight. Participants were given word problems which can be solved quickly with or without insight, and asked to press a button to indicate whether they had solved the problem using insight, which they had been told leads to an Aha! experience characterized by suddenness and obviousness. While several regions in the cerebral cortex showed about the same heightened activity for both insight and noninsight-derived solutions, only an area known as the anterior Superior Temporal Gyrus in the right hemisphere showed a robust insight effect. The researchers also found that 0.3 seconds before the subjects indicated solutions achieved through insight, there was a burst of neural activity of one particular type: high-frequency (gamma band) activity that is often thought to reflect complex cognitive processing. This supports the view that the insight process involves integration of distantly related information.
The report appeared in the Open Access journal PLoS Biology. Full reference
Full text available at http://www.plosbiology.org/plosonline/?request=get-document&doi=10.1371/journal.pbio.0020097
http://www.eurekalert.org/pub_releases/2004-04/plos-itb040604.php

Low vitamin B12 compounding factor with Alzheimer's gene

A long-term multidisciplinary project following older people living in Stockholm (average age nearly 83 years) suggests that B12 and folate supplements may particularly benefit those who carry a gene variant that predisposes them to Alzheimer’s. Those who carry the є4 allele version of the apolipoprotein E gene (perhaps 15% of the population) have a greater risk of developing Alzheimer’s disease (On present information, it appears that around a quarter of those who carry one copy of the allele will develop Alzheimer’s, while in those who carry two copies, nearly half will do so.) Carriers of the є4 allele have a smaller hippocampus. Reduced vitamin B12 and folate levels have also been, independently, linked with diminished memory and increased risk for Alzheimer's. Perhaps 10% of adults aged 75 years and older have low B12 or folate. A test of episodic memory found that, among carriers of the є4 ApoE allele, people with normal B12 levels recalled a greater number of words. Those with the high-risk genotype plus low B12 levels were most disadvantaged when participants had just two seconds to encode words.
The finding was published in the April issue of Neuropsychology. Full reference
Full text available at http://www.apa.org/releases/cognitivesupport_article.pdf
http://www.sciencedaily.com/releases/2004/04/040405085355.htm
http://www.postgradmed.com/issues/2001/07_01/dharmarajan.htm
http://www.eurekalert.org/pub_releases/2004-04/apa-lvb033004.php

Alzheimer's drug improves cognition in MS patients

An estimated 50% of multiple sclerosis patients suffer some degree of cognitive impairment. A pilot study suggests that donepezil, a drug widely used for treating dementia in Alzheimer's patients, may improve memory and cognition in MS patients who are mild to moderately cognitively impaired. The trial involved 69 MS patients. Over 65% of those given donepezil showed cognitive improvement, compared to 32% of those receiving a placebo.
The study was presented by Laura Krupp at the American Academy of Neurology 56th Annual Meeting in San Francisco, Calif., on April 27.
http://www.eurekalert.org/pub_releases/2004-04/aaon-adi042004.php

Brain damage found among heavy social drinkers

Almost all knowledge about brain damage due to chronic alcohol consumption has been gathered from alcoholics, generally toward the end of an institutionalized treatment program or many months into abstinence. A new study however, uses magnetic resonance technology to examine brain damage in heavy drinkers who are not in treatment and function relatively well in the community. The study found that frontal white matter NAA – generally considered to be a marker of neuronal damage – was lower in heavy drinkers than light drinkers, and was associated with lower executive and working memory functions. Some of the behaviors that could be associated with the metabolite changes include the inability to apply consequences from past actions, difficulties with abstract concepts of time and money, difficulties with storing and retrieving information, and frequently needing external motivators.
The study appeared in the April issue of Alcoholism: Clinical & Experimental Research. Full reference
http://www.eurekalert.org/pub_releases/2004-04/ace-sab040704.php

Lower temperatures improve outcomes after bypass surgery

One of the possible adverse effects of cardiac bypass surgery is cognitive decline. Researchers have found that patients who were allowed an additional 10 to 12 minutes to return to normal body temperature after surgery scored almost one-third better on standard tests of cognition six weeks after surgery. (In order to protect the brain and other organs from damage while the heart is stopped during surgery, physicians cool a patient's blood as it passes through a heart-lung machine. However, toward the end of the operation, this blood needs to be rewarmed.)
The results were presented by Hilary Grocott on April 26 at the annual scientific sessions of the Society of Cardiovascular Anesthesiologists.
http://www.eurekalert.org/pub_releases/2004-04/dumc-lti042004.php

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