News reports of research into memory April 2006

Age-related vision problems may be associated with cognitive impairment

Age-related macular degeneration (AMD) develops when the macula, the portion of the eye that allows people to see in detail, deteriorates. An investigation into the relationship between vision problems and cognitive impairment in 2,946 patients has been carried out by The Age-Related Eye Disease Study (AREDS) Research Group. Tests were carried out every year for four years. Those who had more severe AMD had poorer average scores on cognitive tests, an association that remained even after researchers considered other factors, including age, sex, race, education, smoking, diabetes, use of cholesterol-lowering medications and high blood pressure. Average scores also decreased as vision decreased. It’s possible that there is a biological reason for the association; it is also possible that visual impairment reduces a person’s capacity to develop and maintain relationships and to participate in stimulating activities.
The study appeared in the April issue of Archives of Ophthalmology. Full reference
http://www.eurekalert.org/pub_releases/2006-04/jaaj-avp040606.php

AIDS-related cognitive impairment exists in two separate forms

Cognitive impairment in people with AIDS is caused when the HIV virus attacks the brain and can be a complicated syndrome resulting in deficits in mood, behavior, motor coordination and thought processes. While the incidence of severe dementia in people with AIDS has decreased significantly, a greater number of people are living with a milder form of cognitive impairment. A study of 54 participants with AIDS and 23 HIV-negative control subjects has found that cognitive impairment in people with AIDS exists in two forms -- one mild, another severe -- each affecting different areas of the brain. Of the 54 participants with AIDS, 17 demonstrated some level of mental impairment. The mild impairment group only showed problems in the area of psychomotor speed, and demonstrated atrophy in the frontal and anterior cingulate cortices. Those in the severe impairment group showed impairments in memory and visual-spatial processing as well as psychomotor speed, and had more significant atrophy that was located in the caudate and putamen.
The findings were presented April 5 at the American Academy of Neurology 58th Annual Meeting in San Diego.
http://www.eurekalert.org/pub_releases/2006-04/uopm-aci040306.php

More on why older adults are more distractible

A number of recent studies have made it clear that as we age, we find it harder to block out unwanted distractions. A new study used a new brain imaging technique known as EROS to determine whether this is due to faster sensory memory decay or to inefficient filtering of irrelevant sensory information. The study involved 16 young and 16 older participants who read a book of their choice while distracting tones played in the background. The volume of the tones was adjusted so that all the participants heard them at the same level, and the tones were emitted in groups of fives. The young participants showed brain activity in the auditory cortex in response to the first tone in each sequence only, but the older adults' brains responded to all five. The finding supports the view that the growing difficulty at blocking out distractions is due to inefficient filtering of irrelevant sensory information , not faster sensory memory decay.
This research was published in the April issue of the Journal of Cognitive Neuroscience and featured in Scientific American Mind, April/May 2006. Full reference
http://www.sciencentral.com/articles/view.htm3?article_id=218392783

Prenatal exposure to urban air pollutants affects cognitive development

A study of 183 three-year-old children of non-smoking African-American and Dominican women residing in New York City has found that exposure during pregnancy to combustion-related urban air pollutants (specifically, polycyclic aromatic hydrocarbons) was linked to significantly lower scores on mental development tests and more than double the risk of developmental delay at age three.
The study was published onlineon April 24 in Environmental Health Perspectives. Full reference
Full text is available at http://www.ehponline.org/members/2006/9084/9084.pdf
http://www.eurekalert.org/pub_releases/2006-04/cums-iue042506.php

Neurogenesis not the sole cause of enriched environment effects

The creation of new neurons in the hippocampus (adult neurogenesis) and improved cognitive function have been repeatedly found in tandem with a more stimulating environment, and it’s been assumed that the improvement in cognitive function has resulted from the neurogenesis. However, a new study has produced the startling finding that if neurogenesis is prevented, an enriched environment still produces improved spatial memory skills and less anxiety in mice. This doesn't mean adult neurogenesis plays no role, but it does indicate that neurogenesis is not the whole story.
The findings were published online 30 April in Nature Neuroscience. Full reference
http://sciencenow.sciencemag.org/cgi/content/full/2006/503/1?etoc

Specific brain region for reading

Although a number of imaging studies have provided support for the idea that there’s a specific area of the brain that enables us to read efficiently by allowing us to process the visual image of entire words, the question is still debated — partly because the same area also seems to be involved in the recognition of other objects and partly because damage in this region has never been confined to this region alone. Now the experience of an epileptic requiring removal of a small area next to the so-called visual word-form area (VWFA) in the left occipito-temporal cortex has provided evidence of the region's importance for reading. After the operation, the patient’s ability to comprehend words was dramatically slower, and the results were consistent with him reading letter by letter. A brain scan confirmed that the VWFA no longer lit up when words were read, perhaps because the surgery severed its connection to other parts of the brain.
The case study was reported in the 20 April issue of Neuron. Full reference
http://sciencenow.sciencemag.org/cgi/content/full/2006/419/2?etoc
http://www.sciam.com/article.cfm?chanID=sa003&articleID=000D3A4E-A8D1-1446-9A6283414B7F0000

Fast language learners have more white matter in auditory region

An imaging study has found that fast language learners have more white matter in a region of the brain that’s critical for processing sound. The study involved 65 French adults in their twenties, who were asked to distinguish two closely related sounds (the French 'da' sound from the Hindi 'da' sound). There was considerable variation in people’s ability to learn to tell these sounds apart — the fastest could do it within 8 minutes; the slowest were still guessing randomly after 20 minutes. The 11 fastest and 10 slowest learners were then given brain scans, revealing that the fastest learners had, on average, 70% more white matter in the left Heschl's gyrus than the slowest learners, as well as a greater asymmetry in the parietal lobe (the left being bigger than the right).
The findings were published online ahead of print on April 7 in Cerebral Cortex. Full reference
http://www.newscientist.com/article.ns?id=dn8964&print=true

New understanding of how neurons communicate

Although we knew that the release of neurotransmitters at the synapses of neurons causes the voltage inside the neuron to fluctuate continuously — an analog signal — it’s always been thought that the axon was impassable to those fluctuations, and thus that neurons can only communicate with each other through a digital code — that is, by sending out signals whose information is reading in the timing of the pulses. A new study now suggests that the analog signal can indeed travel along the axon, and that the digital signal passed between synapses is influenced by that analog signal. The discovery may lead to a better understanding of disorders such as epilepsy and migraine, both of which involve large changes in the voltage inside neurons.
The study was published online April 12 in Nature. Full reference
http://www.yale.edu/opa/newsr/06-04-12-04.all.html

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