News reports of research into memory July 2007

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July 2007

Testing one time is not enough

A study demonstrating the perils of one-time testing gave 16 common cognitive and neuropsychological tests to groups of people ages 18-39, 50-59 and 60-97 years. The variation between scores on the same test given three times during a two-week period was as big as the variation between the scores of people in different age groups. “It's as if on the same test, someone acted like a 20-year-old on a Monday, a 45-year-old on Friday, and a 32-year-old the following Wednesday”. The study makes clear the dangers of diagnosing learning disability, progressive brain disease or impairment from head injury on the basis of testing on a single occasion. The researcher suggests we should view cognitive abilities as a distribution of many potential levels of performance instead of as one stable short-term level; that people have a range of typical performances, a one-person bell curve. It may also be that within-person variability could be a useful diagnostic marker in itself — for example, extreme fluctuations might be an early warning of mental decline.
The study is detailed in the July issue of Neuropsychology. Full reference
Full text is available at http://www.apa.org/journals/releases/neu214401.pdf)
http://www.physorg.com/news102689828.html
http://www.eurekalert.org/pub_releases/2007-07/apa-csv062507.php

Difficulty identifying odors may predict cognitive decline

Older adults who have difficulty identifying common odors may have a greater risk of developing mild cognitive impairment, increasingly recognized as a precursor to Alzheimer’s disease. A study of nearly 600 older adults (average age 79.9) found that 30.1% developed mild cognitive impairment over the five-year period of the study. Risk of developing mild cognitive impairment was greater for those who scored worse on an odor identification test given at the start of the study. For example, those who scored below average (eight) were 50% more likely to develop MCI than those who scored above average (11). This association did not change when stroke, smoking habits or other factors that might influence smell or cognitive ability were considered. Impaired odor identification was also associated with lower cognitive scores at the beginning of the study and with a more rapid decline in episodic memory (memory of past experiences), semantic memory (memory of words and symbols) and perceptual speed. The odor test involved identifying 12 familiar odors given four possible alternatives to choose from.
The report appeared in the July issue of Archives of General Psychiatry. Full reference
http://www.eurekalert.org/pub_releases/2007-07/jaaj-dio062807.php

Memory problems and sleep disturbance linked in older women

A large long-running study, involving older women (average age 69) found that the nearly 25% of women who experienced cognitive decline over the 15 year period were twice as likely as women without memory problems to experience sleep disturbances, specifically problems staying asleep, and also problems falling asleep and being awake for more than 90 minutes during their sleep cycle. Women who declined on one of the two cognitive tests were also nearly twice as likely to nap more than two hours a day. However, cognitive decline was not associated with total sleep time. The association between sleep disturbances and poor cognitive function is of course well-known, but these findings raise the possibility that cognitive decline may increase the risk of sleep problems, rather than vice versa.
The study was published in the July 17 issue of Neurology. Full reference
http://www.eurekalert.org/pub_releases/2007-07/aaon-oww071007.php

Reading ability protects brain from lead exposure

Cognitive reserve is a concept that has been chiefly discussed in terms of protecting against age-related cognitive decline and Alzheimer’s, but a new study has found evidence that it can also protect against long-term lead exposure. The study of 112 smelter workers found that the cognitive effects of lead were 2.5 times greater in workers with low reading ability, compared to those with high reading ability (defined as a reading level of 12^th grade or higher). Motor speed, however, was comparable in both groups — demonstrating that the nervous system was impaired similarly in both groups.
The study was published in the July 31 issue of Neurology. Full reference
http://www.eurekalert.org/pub_releases/2007-07/aaon-rap072407.php

More on how short-term memory works

It’s been established that visual working memory is severely limited — that, on average, we can only be aware of about four objects at one time. A new study explored the idea that this capacity might be affected by complexity, that is, that we can think about fewer complex objects than simple objects. It found that complexity did not affect memory capacity. It also found that some people have clearer memories of the objects than other people, and that this is not related to how many items they can remember. That is, a high IQ is associated with the ability to hold more items in working memory, but not with the clarity of those items.
The study was published in the July issue of Psychological Science. Full reference
http://www.eurekalert.org/pub_releases/2007-07/uoo-htb071107.php
http://www.physorg.com/news103472118.html

A gene to better remember traumatic events

It's generally accepted that emotional events are easier to remember than more mundane events, but a new study provides evidence that those who carry a common variant of a gene called ADRA2B may have better recall of emotionally charged moments than those who lack the gene. The mutation causes the deletion of three amino acids in the protein that it encodes. This deletion disrupts the behavior of a receptor for the neurotransmitter noradrenaline, which is known to be involved in emotional memory. In the study, 435 young adults were briefly shown 30 pictures and later wrote descriptions of them. Those with the gene variant could recall up to 80% of the emotionally arousing scenes, while those without the gene could only remember 40% of them. A later study of refugees from the 1994 Rwandan civil war found that those with the gene variant reported (and re-experienced) more distressing wartime memories than those without the variant. The gene variant is believed to be found in 30% of the Caucasian population and 12% of African-Americans.
The study appeared online July 29 in Nature Neuroscience. Full reference
http://www.sciam.com/article.cfm?chanID=sa017&articleID=18E4716D-E7F2-99DF-351642C9346A93D3

You can forget the unhappy past

The concept of memory suppression has been a controversial one, but now a study has shown that people can suppress emotional memories and when they do so, this action is associated with a particular pattern of brain activity. The study involved volunteers studying 40 pairs of photographs in which an image of a neutral human face was paired with an emotionally disturbing image such as a car crash, a wounded soldier, an electric chair or a violent crime scene. They were then put in a MRI scanner and there shown the neutral face images and instructed to either actively recall the associated image or to actively suppress it. About half the time, this action was successful. Two specific regions of the prefrontal cortex appeared to work in tandem to reduce activity in the visual cortex, the hippocampus and amygdala.
The report appeared in the July 13 issue of Science. Full reference
http://www.canada.com/topics/technology/science/story.html?id=0bac8252-6471-46fc-b12b-161f8a999742&k=80975
http://www.physorg.com/news103471796.html
http://www.sciam.com/article.cfm?articleID=BC8C0619-E7F2-99DF-3F561A1A6D5D6118&chanID=sa011
http://www.eurekalert.org/pub_releases/2007-07/uoca-emc071007.php

Work could lead to first drug for post-traumatic stress disorder

Researchers have found the molecular mechanism that governs the formation of fears stemming from traumatic events. It was found that inhibiting a kinase (kinases are enzymes that change proteins) called Cdk5 facilitates the extinction of fear learned in a particular context, while increasing that kinase's activity in the hippocampus led to the fear persisting. The work could lead to the first drug to treat PTSD.
The results were reported online July 15 in Nature Neuroscience. Full reference
http://www.eurekalert.org/pub_releases/2007-07/miot-mim071207.php

Study links manic depression with brain tissue loss

A study has found that bipolar disorder is associated with a reduction in brain tissue — changes that get progressively worse with each relapse. The loss of grey matter tissue is concentrated in areas of the brain that control memory, face recognition and co-ordination (hippocampus, fusiform and cerebellum), and correlated with a decline in cognitive function.
The findings were published online July 9 in the Journal of Biological Psychiatry. Full reference
http://www.eurekalert.org/pub_releases/2007-07/uoe-slm071807.php

Anatomical advantage for second language learners

Based on the size of a small brain region called Heschl's Gyrus (HG) in the left hemisphere, researchers found they could predict who would be more successful in learning 18 words in an invented language (those predicted to be "more successful learners" achieved an average of 97% accuracy in identifying the pseudo words, compared to 63% from those deemed "less successful"). The size of the right HG was not important. The finding was surprising, given that this area, the primary region of the auditory cortex, is typically associated with handling the basic building blocks of sound — whether the pitch of a sound is going up or down, where sounds come from, and how loud a sound is — rather than speech per se.
The study was reported online July 25 in Cerebral Cortex. Full reference
http://www.physorg.com/news104599345.html

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