News reports of research into memory January 2008

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January 2008

Lack of imagination in older adults linked to declining memory

In a study in which older and younger adults were asked to think of past and future events, older adults were found to generate fewer details about past events — and this correlated with an impaired ability to imagine future events. The number of details remembered by older adults was also linked to their relational memory abilities. The findings suggest that our ability to imagine future events is based on our ability to remember the details of previously experienced ones, extract relevant details and put them together to create an imaginary event.
The results appeared in the January issue of Psychological Science. Full reference
http://www.eurekalert.org/pub_releases/2008-01/afps-loi010708.php

Older surgical patients at greater risk for developing cognitive problems

There’s been quite a lot of research on the effects of cardiac surgery on cognitive function, but less is known about the effects of any surgery. Now a study of more than 1000 adult patients of different ages has tested memory and cognitive function before undergoing elective non-cardiac surgery, at the time of hospital discharge, and three months after surgery. It was found that many patients, regardless of age, experienced postoperative cognitive dysfunction (POCD) at the time they left the hospital (36.6% of young adults, 30.4% of the middle-aged, 41.4% of elderly). But three months later, those aged 60 and older were more than twice as likely to exhibit POCD (12.7% compared to less than 6% for both young and middle-aged). POCD was more common among those patients with lower educational level and a history of a stroke that had left no noticeable neurologic impairment. Those with POCD at both the time of hospital discharge and three months after surgery also were more likely to die within the first year after surgery. The reason for this is unclear, but it’s speculated that patients with prolonged cognitive dysfunction might be less able to take medicines correctly or may not recognize the need to seek medical care for symptoms of complications.
The findings were published in two reports in the January 1 issue of Anesthesiology. Full reference Full reference 2
http://www.eurekalert.org/pub_releases/2008-01/dumc-osp010208.php

Brain connections strengthen during waking hours, weaken during sleep

New research provides support for a much-debated theory that we need sleep to give our synapses time to rest and recover. The human brain is said to expend up to 80% of its energy on synaptic activity, constantly adding and strengthening connections in response to stimulation. The researchers have theorized that we need an ‘off-line period’, when we are not exposed to the environment, to take synapses down. The rodent study has revealed by several measures that synapses are very active when the animal is awake and very quiet during sleep. The researchers feel that these findings support the idea that our brain circuits get progressively stronger during wakefulness and that sleep helps to recalibrate them to a sustainable baseline. This theory is of course opposite to the currently dominant hypothesis, that during sleep synapses are hard at work replaying the information acquired during the previous waking hours, consolidating that information by becoming even stronger.
The report appeared online January 20 in Nature Neuroscience. Full reference
http://www.physorg.com/news120059987.html

Review supports mild memory impairment in pregnancy

A review of 14 studies testing the memory performances of more than 1,000 pregnant women, mothers and non-pregnant women, has found that pregnant women performed significantly worse on some, but not all aspects of the test. The hardest tests for the pregnant women were those that involved new or demanding tasks. Regular, well-practiced memory tasks were unlikely to be affected. The impairment wasn’t large — comparable to the modest deficits you'd find when comparing healthy 20-year-olds with healthy 60-year-olds. However, the impairment was sometimes still evident a year after birth (none looked beyond that point).
The study was published in the November issue of the Journal of Clinical and Experimental Neuropsychology. Full reference
http://www.physorg.com/news121413361.html

Kids learn more when mother is listening

Research has already shown that children learn well when they explain things to their mother or a peer, but that could be because they’re getting feedback and help. Now a new study has asked 4- and 5-year-olds to explain their solution to a problem to their moms (with the mothers listening silently), to themselves or to simply repeat the answer out loud. Explaining to themselves or to their moms improved the children's ability to solve similar problems, and explaining the answer to their moms helped them solve more difficult problems — presumably because explaining to mom made a difference in the quality of the child's explanations.
The research is currently in press at the Journal of Experimental Child Psychology. Full reference
http://www.physorg.com/news120320713.html

Culture influences brain function

In a follow-up to research showing that cultural differences can influence memory and even perception, an imaging study has revealed that these differences are reflected in brain activity patterns. The study involved 10 East Asians recently arrived in the United States and 10 Americans. They were shown a sequence of lines within squares and asked to compare each stimulus with the previous one. In some trials, they judged whether the lines were the same length regardless of the surrounding squares (an absolute judgment). In other trials, they decided whether the lines were in the same proportion to the squares, regardless of absolute size (a relative judgment). In previous studies, Americans were more accurate on absolute judgments, and East Asians on relative judgments. In the current study, the tasks were easy enough that there were no differences in performance between the two groups. However, scanning revealed that Americans, when making relative judgments, showed much greater activity in brain regions involved in attention-demanding mental tasks, than when they were making absolute judgments. East Asians showed the opposite tendency. The effect was greatest for those who identified more closely with their culture.
The results were reported in the January issue of Psychological Science. Full reference
http://www.eurekalert.org/pub_releases/2008-01/miot-mci011108.php

Insight into insight

A study investigating brain rhythms and their dynamics while volunteers solved verbal problems has shed light on insightful problem-solving. The findings indicate that focusing or attending too much on a topic can have a detrimental effect, and that a strong Aha! sensation involves minimal metacognitive (monitoring of one's own thoughts) processes and unconscious or, better yet, automatic, recombination of information. Interestingly, when clues were provided, it was possible to predict success or failure based on the brain state prior to the clue presentation.
The report was published online January 23 in PLoS ONE. Full reference
Full text available at http://www.plosone.org/doi/pone.0001459
http://www.physorg.com/news120290586.html

Getting better at reading minds

Previous imaging studies have enabled researchers to distinguish when people were thinking about different classes of objects: a hammer versus a house, for example. But now researchers have refined pattern recognition software to the point where the program could learn the subtle differences in a specific brain that told it which of ten similar objects the person was thinking of.
The research was published online January 2 in PLoS One. Full reference
Full text at http://www.plosone.org/article/fetchArticle.action?articleURI=info:doi/10.1371/journal.pone.0001394
http://www.sciencentral.com/articles/view.php3?article_id=218393057

Deep brain stimulation may improve memory

In a truly serendipitous and surprising development, experimental brain surgery intended to suppress an obese man's appetite using the increasingly successful technique of deep-brain stimulation, induced an intense recollection of an event from his distant past. More tests showed his ability to learn was dramatically improved when the current was switched on and his brain stimulated. Scientists are now applying the technique in the first trial of the treatment in 6 patients with Alzheimer's disease. The effect is surprising in that it involves stimulation of the hypothalamus, a critical region for metabolic regulation, but not one that has ever been associated with memory. However, the best contact was in a place close to the fornix, an arched bundle of fibres that carries signals within the limbic system, which is involved in memory and emotions and is situated next to the hypothalamus. Deep brain stimulation has been used for some time to treat Parkinson’s disease and other movement disorders.
The study was published in the January issue of Annals of Neurology. Full reference
http://www.independent.co.uk/news/science/scientists-discover-way-to-reverse-loss-of-memory-775586.html
http://www.eurekalert.org/pub_releases/2008-01/w-dbs012408.php

Hypnosis study sheds insight on amnesia

An intriguing study investigating brain activity of hypnotically induced forgetting may shed light on amnesia. Researchers showed volunteers a documentary depicting a day in the life of a young woman, followed a week later with a brain scan while they were put into a hypnotic state. They were given a posthypnotic suggestion to forget the movie, and a reversibility cue that would restore the memory. When their recall of the movie was later tested, those susceptible to posthypnotic amnesia showed reduced recall. Brain scans revealed different brain activity patterns between those susceptible and those who were not. For the susceptible, activity in some brain regions was suppressed during memory suppression, while activity in other regions increased. But when the posthypnotic suggestion was reversed, the susceptible group showed recovery of activity in suppressed regions. The findings suggest that suppression was exerted at early stages of the retrieval process, specifically, an executive pre-retrieval monitoring process that produces an early decision on whether to proceed or not on retrieval. The researchers suggest that some forms of amnesia may be a consequence of this ‘preretrieval memory abort’ mechanism.
The findings appeared in the January 10 issue of Neuron. Full reference
http://www.eurekalert.org/pub_releases/2008-01/cp-hsr010408.php

Novel mechanism for long-term learning identified

There has always been a paradox at the heart of learning: repetition is vital, yet at the level of individual synapses, repetitive stimulation might actually reverse early gains in synaptic strength. Now the mechanism that resolves this apparent paradox has been uncovered. N-methyl-D-aspartate (NMDA) receptors appear from studies to be required for the synaptic strengthening that occurs during learning, but these receptors undergo a sort of Jekyll-and-Hyde transition after the initial phase of learning. Instead of helping synapses get stronger, they actually begin to weaken the synapses and impair further learning. The new study reveals that while the NMDA receptor is required to begin neural strengthening, a second neurotransmitter receptor — the metabotropic glutamate (mGlu) receptor — then comes into play. Using an NMDA antagonist to block NMDA receptors after the initiation of plasticity resulted in enhanced synaptic strengthening, while blocking mGlu receptors caused strengthening to stop.
The findings were published in the January 4 issue of Science. Full reference
http://www.eurekalert.org/pub_releases/2008-01/cmu-nmf010308.php

New genetic link to autism identified

Three new studies, using different methods, have all implicated the same gene in the development of autism. The research follows earlier findings implicating a specific region of Chromosome 7 called 7q35. The gene — contactin-associated protein-like 2 (CNTNAP2) — is a gene in this region. The research not only points to this gene predisposing an individual to autism, it also may explain the association with late language onset, a characteristic of most autistic children. The gene was most active in developing brain structures involved in language and thought. The finding may also help explain why autism is so much more common among boys. Statistical evidence for the gene was strongest in families with autistic boys. Less of an association appeared in families with autistic boys and girls, or in families with autistic girls only.
The studies were all published in the January 10 issue of The American Journal of Human Genetics. Full reference Full reference 2 Full reference 3
http://www.eurekalert.org/pub_releases/2008-01/uoc--usi010808.php

Study raises questions about diagnosis, treatment of ADHD

The first large, longitudinal study of adolescents and ADHD has revealed that only about half of children diagnosed with attention-deficit hyperactivity disorder exhibit the cognitive defects commonly associated with the condition. Part of the explanation may lie in the fact that ADHD is simply the extreme end of a normal continuum of behavior that varies in the population, and its diagnosis is defined by where health professionals "draw the line" on this continuum. This finding suggests that behavior-rating scales alone are not sensitive enough to differentiate between the two groups. Researchers also found surprising results regarding the effectiveness of medicine in treating ADHD. In contrast to children in United States, youth in northern Finland are rarely treated with medicine for ADHD, yet the prevalence, symptoms, psychiatric comorbidity and cognition of the disorder is relatively the same as in the U.S., where stimulant medication is widely used. Although the medication is very effective in the short-term, the study raises questions concerning its long-term efficacy. The study also confirmed that hyperactivity and impulsivity decrease with age, while inattention increasingly predominates; that ADHD is associated with increased rates of other psychiatric problems, especially depression, anxiety, oppositional behaviors, conduct disorders, and post-traumatic stress disorder. The study of Finnish adolescents found a prevalence of 8.5% with a male/female ratio of 5.7:1.
Findings of the study appeared in several papers in a special section of the December issue of the Journal of the American Academy of Child and Adolescent Psychiatry. Full reference Full reference 2 Full reference 3 Full reference 4
http://www.eurekalert.org/pub_releases/2008-01/uoc--srq012208.php

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