News reports of research into memory August 2004

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August 2004

Tests for working memory capacity more limited than thought

The so-called “magic number 7” has been a useful mnemonic for working memory capacity — how many items you can hold in your working memory at one time — but we’ve known for some time that it isn’t quite as it was originally thought. Apart from the fact that the “7” is an average, and that the idea of an “item” is awfully vague as far as informational content is concerned, we have known for some time that what is really important is how long it takes for you to say the words. Thus, Chinese can hold on average 9 items, because the words used in the test are short and simple to pronounce, whereas the Welsh can hold only 5 on average, because of the length and complexity of their words. (note: it’s not because we actually say these words out loud). Similarly, the finding that deaf users of American Sign Language have an average of only 5 items was thought to be because signs take longer to utter. However, new research casts doubt on this theory. The researchers were trying to devise a sign-language test that would be comparable to a hearing language test. To their surprise they found that even when signs were faster to pronounce than spoken language, signers recalled only five items. Also, hearing individuals who were fluent in American Sign Language scored differently when asked to recall spoken lists in order, versus when they recalled signed lists (seven heard items remembered, five signed items remembered). Up until this time, the predominant idea was that the number found by this test was a good measure of overall cognitive capacity, but this assumption must now be in doubt. It's suggested that a test requiring recall of items, but not in temporal order, is a better measure of cognitive capacity. The results have important implications for standardized tests, which often employ ordered-list retention as a measure of a person's mental aptitude.
The report appeared as the cover story of the 15 August issue of Nature Neuroscience. Full reference
http://www.eurekalert.org/pub_releases/2004-08/uor-stm083104.php

More support for the benefits of blueberries

Several recent studies have provided evidence for the benefits of blueberries in preventing age-related cognitive decline. Consistent with this, and with the linking of cholesterol levels and age-related cognitive decline, is a new study suggesting a compound in blueberries may lower cholesterol as effectively as a commercial drug, with the potential for fewer side effects. The compound pterostilbene is an antioxidant that is similar to resveratrol, an antioxidant identified in grapes and red wine that is also believed to lower cholesterol. Pterostilbene has also been implicated in helping fight cancer, as well as having anti-diabetic properties.
The findings were presented on August 23 at the 228^th national meeting of the American Chemical Society.
http://www.eurekalert.org/pub_releases/2004-08/acs-cs_1081604.php

Estrogen effect on memory influenced by stress

The question of whether estrogen helps memory and cognition in women has proven surprisingly difficult to answer, with studies giving conflicting results. Now it seems the answer to that confusion is: it depends. And one of the things it depends on may be the level of stress the woman is experiencing. A rat study has found that the performance of female rats in a water maze was affected by the interaction of hormone level (whether the rat was estrous or proestrous) with water temperature (a source of physical stress). Those rats with high hormone levels did better when the water was warm, while those with low hormone levels did better when the water was cold. The researchers suggest both timing and duration of stress might be factors in determining the effect of hormones on cognition.
The report appeared in the August issue of Behavioral Neuroscience. Full reference
http://www.eurekalert.org/pub_releases/2004-08/uoia-sss082704.php

Dyslexics have less gray matter in the brain's language centers

A new imaging study involving people with a family history of dyslexia confirms earlier research suggesting dyslexics have a significant reduction of gray matter in centers associated with language processing. The study lends credence to earlier studies that suggested intensive reading therapy activates parts of the brain needed for decoding words.
The finding was published in the August 24 issue of Neurology. Full reference

Growing up in a chaotic home may impair child's cognitive development

An association between disorganized, noisy and cramped homes and lower childhood intelligence has been observed before, but the reasons for the association have never been clear. Now a study of some 8000 3- and 4-year-old twins has perhaps disentangled the variables, and has found that chaos had an influence on cognitive skills independent of socioeconomic status. The findings also suggest that when the environment is more stressful, intelligence is more likely to be constrained by genes.
The report appeared in the September-October issue of Intelligence. Full reference
http://www.newscientist.com/news/news.jsp?id=ns99996323

Effect of prematurity on brain worse for boys

A comparison of the brain volumes of 65 8-year-olds born prematurely to 31 children born full-term has found significantly smaller areas in the cerebral cortex, especially in parts responsible for reading, language, emotion and behavior. However, significant gender differences were found. Only the preterm boys showed significant reductions in white matter volume. Only the preterm girls showed a positive correlation between gray matter volume and cognitive outcome. The study suggests that the gender of the preterm child affects the way in which the developing brain is affected, and also suggests that boys are more negatively affected by prematurity. Previous studies have indicated more adverse cognitive outcomes for preterm boys than preterm girls. This latest study suggests that an approach to stimulate white matter growth in preterm boys would be promising.
The report appeared in the August issue of the Journal of Pediatrics. Full reference
http://www.msnbc.msn.com/id/5648757/

New radiation therapy of brain tumors in children spares cognitive functions

The second phase of a clinical trial for ependymoma (a malignant brain tumor that occurs predominately in children) suggests a radiation therapy technique called conformal radiation therapy (CRT) allows young patients to enjoy normal development of their cognitive functions. About 75% of the 88 children treated for ependymoma with CRT did not experience progression of their cancer after three years, and their cognitive development was not significantly impaired by radiation therapy. Although radiation treatment is more effective than chemotherapy for brain tumors, physicians have been reluctant to use it because of fears of impairing cognitive development in young children.
This research is published in the August issue of the Journal of Clinical Oncology. Full reference
http://www.eurekalert.org/pub_releases/2004-08/sjcr-3io080504.php

New hope for children with fetal alcohol syndrome

A study of 415 people diagnosed with either fetal alcohol syndrome (FAS) or fetal alcohol effect (FAE) found two factors greatly increased the chances of escaping the negative experiences common to those with such problems - being diagnosed early in life and being raised in a stable and nurturing environment. These findings offer hope in a situation that many have regarded as hopeless.
The report appeared in the Aug. 12 edition of the Journal of Developmental and Behavioral Pediatrics . Full reference
http://www.eurekalert.org/pub_releases/2004-08/uow-nhf081004.php

Possible benefits of alcohol in reducing cognitive decline

Another report from the Whitehall Study database. This one adds to the, still controversial, research linking moderate wine consumption with health and longevity. Of those who reported drinking alcohol in the past year, those who consumed at least one drink in the past week were significantly less likely to have poor cognitive function than those who did not. These benefits appeared even at levels of alcohol consumption that most sensible observers would consider excessive, and emphasizes once again that correlation is not causation. It seems likely that this association at least partly reflects other factors, and indeed, the correlation was reduced when social position was taken account of. It may also reflect the possible effect of alcohol in reducing risk of cardiovascular disease.
http://www.telegraph.co.uk/news/main.jhtml?xml=/news/2004/08/01/nalco01.xml

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