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News reports of research into memory October 2001

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October 2001

A comparison of memory performance in recent users of the drug Ecstasy, ex-users, and those who have never taken the drug, indicates Ecstasy may cause permanent damage to cognitive function. It appears that ecstasy damages mechanisms associated with serotonin, particularly in an area of the brain linked to memory.
The study was published in The Archives of General Psychiatry. Full reference
http://tinyurl.com/ix9f

A recent study uses EEG readings to investigate gender differences in the emerging connectivity of neural networks associated with phonological processing, verbal fluency, higher-level thinking and word retrieval (skills needed for beginning reading), in preschoolers. The study confirms different patterns of growth in building connections between boys and girls. These differences point to the different advantages each gender brings to learning to read. Boys favor vocabulary sub-skills needed for comprehension while girls favor fluency and phonic sub-skills needed for the mechanics of reading.
The findings were presented at Genomes and Hormones: An Integrative Approach to Gender Differences in Physiology, an American Physiological Society (APS) conference held October 17-20 in Pittsburgh. Reference http://www.eurekalert.org/pub_releases/2001-10/aps-gad101701.php

We have long known that learning can occur without attention. A recent study demonstrates learning that occurs without attention, without awareness and without any task relevance. Subjects were repeatedly presented with a background motion signal so weak that its direction was not visible; the invisible motion was an irrelevant background to the central task that engaged the subject's attention. Despite being below the threshold of visibility and being irrelevant to the central task, the repetitive exposure improved performance specifically for the direction of the exposed motion when tested in a subsequent suprathreshold test. These results suggest that a frequently presented feature sensitizes the visual system merely owing to its frequency, not its relevance or salience.
The report appeared in the 25 October issue of Nature. Full reference
http://www.nature.com/nsu/011025/011025-12.html
http://tinyurl.com/ix98

While the formation of new memories is reasonably well understood, exactly how memories are stored is still a mystery. A recent study points to the significance of protein synthesis in that part of brain cells called dendrites. Dendrites are long structures that extend out from the cell body. Cell bodies store the genetic code (the DNA) so a message, mRNA, which is made from the DNA, moves from the cell body to dendrites. Neuronal dendrites are known to pick up and convey information in the form of electrical pulses, but they could also store information by synthesizing proteins from mRNA templates.
The report was published in the Proceedings of the National Academy of Science on October 23. Full reference
http://www.eurekalert.org/pub_releases/2001-10/uopm-pip102201.php

A recent study that compared episodic memory (for events) and implicit memory (for facts) concluded that the two hemispheres of the brain work together to help us remember events, while facts are processed in one hemisphere alone. It seems that people whose brains' halves work together more actively (people with left-handedness in their families - although not necessarily left-handed themselves) remember events better than they remember facts. These findings also help explain why children don't remember events until about age 4, when the fibers connecting the hemispheres fully develop.
This research was reported in the October issue of Neuropsychology. Full text of the article is available at http://www.apa.org/journals/neu.html Full reference

http://www.apa.org/releases/leftymemory.html

An imaging study that sheds light on the gain in performance observed during the day after learning a new task. Following training in a motor skill, certain brain areas appear to be reactivated during REM sleep, resulting in an optimization of the network that subtends the subject's visuo–motor response.
The report appeared in the October issue of Neuroscience. Full reference
http://tinyurl.com/ix9b

Imaging studies continue apace! Having established that that part of the brain known as the fusiform gyrus is important in picture naming, a new study further refines our understanding by studying the cerebral blood flow (CBF) changes in response to a picture naming task that varied on two dimensions: familiarity (or difficulty: hard vs easy) and category (tools vs animals). Results show that although familiarity effects are present in the frontal and left lateral posterior temporal cortex, they are absent from the fusiform gyrus. The authors conclude that the fusiform gyrus processes information relating to an object's structure, rather than its meaning. The blood flows suggest that it is the left posterior middle temporal gyrus that is involved in representing the object's meaning.
The report appeared in Neuropsychologia. Full reference

Another imaging study. This one provides evidence that the bilateral fronto-polar prefrontal cortices are involved in learning rules governing category membership. This supports the role of this region in reasoning and problem-solving.
The report appeared in the November issue of Cerebral Cortex. Full reference
http://cercor.oupjournals.org/cgi/content/abstract/11/11/1040

Goal-directed behaviour depends on keeping relevant information in mind (working memory) and irrelevant information out of mind (behavioural inhibition or interference resolution). Prefrontal cortex is essential for both working memory and for interference resolution, but it is unknown whether these two mental abilities are mediated by common or distinct prefrontal regions. An imaging study found there was a high degree of overlap between the regions activated by load and interference, while no region was activated exclusively by interference. The findings suggest that, within the circuitry engaged by this task, some regions are more critically involved in the resolution of interference whereas others are more involved in the resolution of an increase in load.
The report appeared in the October issue of Brain. Full reference
http://brain.oupjournals.org/cgi/content/abstract/124/10/2074

An imaging study compared activation patterns of adults with autism and normal control subjects during a face perception task. While autistic subjects could perform the face perception task, none of the regions supporting face processing in normals were found to be significantly active in the autistic subjects. Instead, in every autistic patient, faces maximally activated aberrant and individual-specific neural sites (e.g. frontal cortex, primary visual cortex, etc.), which was in contrast to the 100% consistency of maximal activation within the traditional fusiform face area (FFA) for every normal subject. It appears that, as compared with normal individuals, autistic individuals `see' faces utilizing different neural systems, with each patient doing so via a unique neural circuitry.
The report appeared in the October issue of Brain. Full reference
http://brain.oupjournals.org/cgi/content/abstract/124/10/2059

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