News reports of research into memory May 2004

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May 2004

Diabetics at significantly higher risk for Alzheimer's disease

New findings from the Religious Orders Study add to research suggesting a link between diabetes mellitus and an increased risk of developing Alzheimer's disease. Some aspects of cognitive function appear to be affected differently than others, in particular perceptual speed declined significantly faster in those with diabetes.
The study appeared in the May issue of the Archives of Neurology. Full reference
http://www.eurekalert.org/pub_releases/2004-05/rpsl-das051204.php

Confirmation: boys have more literacy problems than girls

Previous research has suggested the reason that reading disabilities are more common among boys is that teachers simply tend to recognize the problem in boys more often. It is sometimes thought that boys are more disruptive, so the teachers pay more attention to them. However, new research investigating four previous large-scale studies of reading in children (2 New Zealand and 2 U.K.), involving a total of some 9,800 children, seems to make it clear that boys really do have more reading difficulties than girls. Across all the studies, about 20% of the boys had reading disabilities compared with about 11% of the girls. The studies used representative samples of children, not simply children already known to be having learning difficulties - a weakness of some previous research.
The study was reported in the April 28 issue of the Journal of the American Medical Association. Full reference
http://www.eurekalert.org/pub_releases/2004-05/uow-rrf051304.php

Impact of iron deficiency in infancy continues into adolescence

A new study has found that teens who suffered iron deficiency as infants are likely to score lower on cognitive and motor tests, even if that iron deficiency was identified and treated in infancy. The study followed 191 children. Those who were diagnosed with severe, chronic iron deficiency when they were 12-23 months old and were treated with iron supplements, lagged behind their peers in both motor and mental measures. The difference, moreover, actually increased over time. The iron-deficient infants scored about six points lower on cognitive tests at age 1-2 years, and 11 points lower at age 15-18 years. The gap was even more pronounced for children of families with low socioeconomic status, lower stimulation in the home or mothers lower in IQ. For children with good iron status, family conditions did not seem to affect their cognitive test scores. The researcher stressed that the children were not generally malnourished. Moreover, it must be emphasized that these children received treatment for their iron deficiency, yet still showed continuing ill effects, pointing to the need to prevent the deficiency occurring in the first place.
The study was presented at the Pediatric Academic Societies' annual meeting on May 3 in San Francisco. Reference
http://www.eurekalert.org/pub_releases/2004-05/uom-iis050404.php

American Academy of Pediatrics information on iron intake for infants: http://aappolicy.aappublications.org/cgi/content/full/pediatrics;104/1/119

More on effects of sleep loss and fatigue on memory and learning

Just to confirm what we all know (I hope): a study of medical residents from five U.S. academic health centers has found that sleep loss and fatigue affect learning, job performance and personal relationships. Specifically, residents reported adverse effects on their abilities to learn, either in short-term or long-term memory of material; on their motivation to learn; and on their higher-order thinking skills (cognitive abilities and complex thinking).
The research paper appears in a special theme issue on medical residents in the May issue of Academic Medicine.
Full reference
http://www.eurekalert.org/pub_releases/2004-05/cwru-mrr050404.php

Memories of crime stories influenced by racial stereotypes

The influence of stereotypes on memory, a well-established phenomenon, has been demonstrated anew in a study concerning people's memory of news photographs. In the study, 163 college students (of whom 147 were White) examined one of four types of news stories, all about a hypothetical Black man. Two of the stories were not about crime, the third dealt with non-violent crime, while the fourth focused on violent crime. All four stories included an identical photograph of the same man. Afterwards, participants reconstructed the photograph by selecting from a series of facial features presented on a computer screen. It was found that selected features didn’t differ from the actual photograph in the non-crime conditions, but for the crime stories, more pronounced African-American features tended to be selected, particularly so for the story concerning violent crime. Participants appeared largely unaware of their associations of violent crime with the physical characteristics of African-Americans.
The study was reported in the March issue of the Journal of Communication. Full reference
http://www.eurekalert.org/pub_releases/2004-05/ps-rmo050504.php

Confirmation that a memory code is held in many different regions

Mapping of brain activity patterns has cast new light on how our memories integrate sights, smells, tastes, and sounds. Previous research has shown that the visual and auditory brain regions are activated during memories of pictures and sounds. A new imaging study investigated taste and smell. Volunteers were presented with random combinations of an odor and the image of an object and asked to imagine a link or story that associated the two. They were then presented with a series of both previously seen images and new images and asked to recall whether they were viewing new or old images. It was found that the region involved in processing smells, the piriform cortex, was activated when participants saw objects previously associated with odors. On questioning, participants said they recalled the story linking image and smell, but had not tried to summon up the smell itself. These findings confirm models of memory recall in which the sensory-specific components of a memory are preserved in the sensory-related brain regions, and the hippocampus draws on those components to reconstruct a sensory-rich memory (as opposed to the complete memory being stored in one place). This allows memories to be recalled from one sensory cue.
The research was reported in the May 27 issue of Neuron. Full reference
http://www.eurekalert.org/pub_releases/2004-05/cp-hoh052104.php
http://www.eurekalert.org/pub_releases/2004-05/ucl-ros052404.php

Role of hippocampus in long term memory

The role of the hippocampus in the formation of new memories has been well-documented, and we know that the hippocampus is involved in transferring immediate or short-term memories into long-term memories. However, its specific contribution to the representation of very well-learned information is not well understood. Now a study has recorded the activity of individual hippocampal neurons as monkeys retrieved information from memory, demonstrating significantly different response when the stimuli were well-learned, compared to novel stimuli. This differentiated response in the hippocampus provides strong evidence for a memory signal specific for well-learned information, and suggests a way for well-learned information to be incorporated into everyday memories.
The study was published in the May 13 issue of Neuron. Full reference
http://www.eurekalert.org/pub_releases/2004-05/nyu-ssh051204.php

Seeing the formation of a memory

An optical imaging technique has enabled researchers to visualize changes in nerve connections. The study used genetically modified fruit flies, whose neuronal connections become fluorescent during synaptic transmission. The flies were conditioned to associate a brief puff of an odor with a shock. Using a high-powered microscope to watch the fluorescent signals in flies' brains as they learned, the researchers discovered that a specific set of neurons (projection neurons), had a greater number of active connections with other neurons after the conditioning experiment. These newly active connections appeared within 3 minutes after the experiment, suggesting that the synapses which became active after the learning took place were already formed but remained "silent" until they were needed to represent the new memory. The new synaptic activity disappeared by 7 minutes after the experiment, but the flies continued to avoid the odor they associated with the shock. The study suggests that the earliest representation of a new memory occurs by rapid changes – "like flipping a switch" – in the number of neuronal connections that respond to the odor, rather than by formation of new connections or by an increase in the number of neurons that represent an odor. The fact that the flies continued to show a learned response even after the new synaptic activity waned suggests that other memory traces found at higher levels in the brain took over to encode the memory for a longer period of time.
The research appeared in the May 13 issue of Neuron. Full reference
http://www.eurekalert.org/pub_releases/2004-05/nion-sar051004.php

Hippocampus and subiculum both critical for short-term memory

A new animal study has revealed that the hippocampus shares its involvement in short-term memory with an adjacent brain region, the subiculum. Both regions act together to establish and retrieve short-term memories. The process involves each region acting at different times, with the other region shutting off while the other is active. The shortest memories (10-15s) were found to be controlled almost exclusively by the subiculum. After 15s, the hippocampus took over. It was also found that the hippocampus appeared to respond in a way influenced by previous experiences, allowing it to anticipate future events on the basis of past outcomes. This is an advantage but can also cause errors.
The research was reported in the May 13 issue of Neuron. Full reference
http://www.eurekalert.org/pub_releases/2004-05/wfub-nrs050604.php

Small world networks key to memory

A computer model may reveal an important aspect of working memory. The key, researchers say, is that the neurons form a "small world" network. In such a network, regardless of its size, any two points within them are always linked by only a small number of steps. Working memory may rely on the same property.
http://www.newscientist.com/news/news.jsp?id=ns99995012

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