News reports of research into memory November 2003

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November 2003

Emotions help memory, at the cost of other memories

Do we remember emotionally charged events better? Maybe — but at a price. A new study presented volunteers with lists of neutral words with one disturbing noun, such as murder or scream, embedded. As expected, the emotional words were much better remembered than the neutral words. More interestingly, the poorest memory occurred for neutral words that were presented immediately before the disturbing words. The effect was greater for women — women forgot those words twice as often as men.
The report will be published in an upcoming Proceedings of the National Academy of Sciences. Full reference
http://www.sciencenews.org/20031108/fob5.asp

More support for importance of stimulation to protect against cognitive decline

A British study questioned some 5,350 civil servants aged between 35 and 55 about their participation in 13 leisure activities, ranging from DIY and housework to cultural visits and evening classes. They were then given tests in verbal memory, mathematical reasoning, vocabulary and verbal fluency. Independent of socio-economic position, the highest level of cognitive ability was associated with regular cultural visits to theatres, art galleries and stately homes. This was closely followed by reading and listening to music, then by involvement in clubs and voluntary organisations, and participation in courses and evening classes. The association was stronger among men. While the researchers suggested that seeking mental stimulation may have a beneficial effect on cognition in middle age, and the research was popularly reported as indicating that “going to the pub is good for the brain” (going to the pub was indeed associated with a slightly higher cognitive ability, but less so that the afore-mentioned), it must be remembered that correlation does not imply causation.
The research was published in the Journal of Epidemiology and Community Health. Full reference
http://news.bbc.co.uk/1/hi/health/3239641.stm
http://www.smh.com.au/articles/2003/11/06/1068013332038.html

Low self-esteem 'shrinks brain'

A 15-year study of 92 seniors found that those with a low sense of self worth were more likely to suffer from memory loss as they got older. Moreover, the brains of those with low self-worth were up to a fifth smaller than those who felt good about themselves. It is speculated that those who are anxious and think negatively may set themselves up for memory loss by not bothering to engage themselves in activities that would stimulate and enrich their brains.
The study was presented at a conference at the Royal Society in London.
http://news.bbc.co.uk/2/hi/health/3224674.stm

Magnetic resonance imaging may help predict future memory decline

A six-year imaging study of 45 healthy seniors assessed changes in brain scans against cognitive decline. They found that progressive atrophy in the medial temporal lobe was the most significant predictor of cognitive decline, which occurred in 29% of the subjects.
The study appeared in the December issue of Radiology. Full reference
http://www.eurekalert.org/pub_releases/2003-11/rson-mhr111703.php

Memory-enhancing drugs for elderly may impair working memory and other executive functions

Drugs that increase the activity of an enzyme called protein kinase A improve long-term memory in aged mice and have been proposed as memory-enhancing drugs for elderly humans. However, the type of memory improved by this activity occurs principally in the hippocampus. A new study suggests that increased activity of this enzyme has a deleterious effect on working memory (which principally involves the prefrontal cortex). In other words, a drug that helps you remember a recent event may worsen your ability to remember what you’re about to do (to take an example).
The research was published in the November 13 issue of Neuron. Full reference http://www.eurekalert.org/pub_releases/2003-11/naos-mdf110303.php

Drugs to improve memory may worsen memory in some

A number of pharmaceutical companies are working on developing memory-enhancing drugs not only for patients with clinical memory impairment, but also for perfectly healthy people. Although some drugs have been found that can improve cognitive function in those suffering from impairment, the side effects preclude their use among healthy people. However, a recent study has found evidence that a well-established drug used for narcolepsy (excessive daytime sleepiness) may improve cognition in normal people, without side effects. The drug seems to particularly affect some tasks requiring planning and working memory (and in a further, as yet unpublished study, appears helpful for adults with ADHD). Whether the drug (modafinil) has anything over caffeine in terms of the cognitive benefits it brings is still debated. More interestingly, and in line with the sometimes conflicting results of these kinds of drugs on different people, the researchers suggest that the effect of drugs on cognitive function depends on the level at which the individual cognitive system is operating: if your system is mildly below par, the right brain chemical could improve performance; if it’s well below par, the same dose will have a much smaller effect; if (and this is the interesting one) it’s already operating at peak, the chemical could in fact degrade performance.
The study was reported in the January issue of Psychopharmacology. Full reference
http://gateways.bmn.com/sreport/previous?day=031202&story=1

Population level of frontotemporal dementia

A large-scale epidemiological study in the Netherlands has found an incidence of frontotemporal dementia that equates to a population level of 1.1 per 100,000. The prevalence was highest among those ages 60 to 69, at 9.4 per 100,000. The prevalence among people ages 45 to 64 was estimated to be 6.7 per 100,000. Symptoms began after age 65 in 22% of patients. Whites accounted for 99% of all cases despite an ample nonwhite population. A family history of dementia was present in 43% of patients.
The study was reported in the September issue of Brain. Full reference

Learning involves the death of neurons too

When we think about learning at the neural level, it is always the birth of new neurons and new synaptic connections that is thought of. Now it appears that death is involved too. A recent rat study has found that while new cells are being generated in the hippocampus, other cells are dying off. The study distinguished two phases of learning during a water maze task: the first phase, when the rat learns to navigate the maze; and the second phase, when the learned behavior is refined. During the second phase, it appears, new cells are born in the dentate gyrus, while some of the cells that were born during the first phase, disappear. If true, this could be "a trimming mechanism that suppresses neurons that have not established learning-related synaptic connections."
The findings were reported in the December issue of Molecular Psychiatry. Full reference
http://gateways.bmn.com/news/story?day=031128&story=2
http://www.eurekalert.org/pub_releases/2003-11/mp-cdp112103.php

Some of the research presented at the annual meeting of the Society for Neuroscience, held November 8–12 in New Orleans, LA:

Initial steps in a test for false memory

It appears that sensory areas of the brain might be more revealing than the areas specific involved in memory when trying to tell whether a given memory is true or false. An imaging study has found that when people correctly recognised a shape, a visual area called the ventral temporal cortex was more active than when people mistakenly identified a shape that was only similar. In similar vein, auditory regions of the brain became more active during accurate recognition of words.
http://www.newscientist.com/news/news.jsp?id=ns99994363
http://www.eurekalert.org/pub_releases/2003-11/sfn-sfb110803.php

Support for gingko biloba

A study of seniors with age-associated memory impairment found significant improvement in verbal recall among those who took gingko biloba for six months. PET scans revealed a correlation with better brain function in key brain memory centers, although there was no detectable changes in brain metabolism. Studies of gingko biloba have had conflicting results, and it is suggested that both length of time (most studies have looked at the effect over 3 months or less) and quality of supplement, may be important.
http://www.eurekalert.org/pub_releases/2003-11/uoc--urf111003.php

More support for value of antioxidants in protecting against age-related cognitive decline

Several studies have come out supporting the value of a diet rich in antioxidants to help stave off cognitive impairment in old age. A recent study has found that old dogs on an antioxidant-rich diet performed as well as young animals on a variety of cognitive tests. Young dogs did not benefit from the diet. Two years ago, researchers reported that a blueberry-enriched antioxidant diet may prevent age-related deterioration of object recognition memory in aged rats. A new report, from a study of the same rats, reveals that the diet also prevented an age-related increase in a protein (NF-kappaB) that responds to oxidative stress, a probable cause of brain aging. This adds to growing evidence that a buildup of oxidative damage is an important factor in brain aging. Another rat study has found that blueberries can help lessen some of the damage caused by a brain injury.
http://www.eurekalert.org/pub_releases/2003-11/sfn-dmi110603.php

Beneficial effects of bilingual learning

A recent Canadian study comparing young monolingual children to bilingual found that bilingual children were much better at a non-language cognitive task. The 4-6 year old bilingual children were versed in a spoken language and a signing one. It was suggested that their higher cognitive skill was due to the increased computational demands of processing two different language systems.
http://www.eurekalert.org/pub_releases/2003-11/sfn-ssb111103.php

Immature motion pathways in the brain associated with poor reading skills

An interactive computer game called MovingToRead (MTR) has significantly improved reading skills in poor second-grade readers within three months by practicing left-right movement discrimination for 5 to 10 minutes once or twice a week. It has been suggested that immature motion pathways — the circuit of neurons that helps readers determine the location of letters of a word and words on a page — may be related to reading problems in children. The therapy appears to be most effective with second-graders (age 7).
http://www.eurekalert.org/pub_releases/2003-11/sfn-ssb111103.php

Growing evidence cerebellum involved in language

An imaging study of children with selective problems in short term phonological memory and others diagnosed with specific language impairment (and matched controls) found that those with selective STPM deficits and those with SLI had less gray matter in both sides of the cerebellum compared to the children in the control groups. This supports growing evidence that the cerebellum, an area of the brain once thought to be involved only in the control of movement, also plays a role in processing speech and language.
http://www.eurekalert.org/pub_releases/2003-11/sfn-ssb111103.php

Maturation of the human brain mapped

The progressive maturation of the human brain in childhood and adolescence has now been mapped. The initial overproduction of synapses in the gray matter that occurs after birth, is followed, for the most part just before puberty, with their systematic pruning. The mapping has confirmed that this maturation process occurs in different regions at different times, and has found that the normal gray matter loss begins first in the motor and sensory parts of the brain, and then slowly spreads downwards and forwards, to areas involved in spatial orientation, speech and language development, and attention (upper and lower parietal lobes), then to the areas involved in executive functioning, attention or motor coordination (frontal lobes), and finally to the areas that integrate these functions (temporal lobe). "The surprising thing is that the sequence in which the cortex matures appears to agree with regionally relevant milestones in cognitive development, and also reflects the evolutionary sequence in which brain regions were formed."
http://www.eurekalert.org/pub_releases/2003-11/sfn-smm110803.php

Sleep deprivation affects working memory

A recent study investigated the working memory capacities of individuals who were sleep-deprived. For nine days, 7 of the 12 participants slept four hours each night, and 5 slept for eight hours. Each morning, participants completed a computer task to measure how quickly they could access a list of numbers they had been asked to memorize. The list could be one, three, or five items long. Then participants were presented with a series of single digits and asked to answer "yes" or "no" to indicate whether each digit was one they had memorized. Those who slept eight hours a night steadily increased their working memory efficiency on this task, but those who slept only four hours a night failed to show any improvement in memory efficiency. Motor skill did not change across days for either group of participants.
http://www.eurekalert.org/pub_releases/2003-11/sfn-sfb_1111003.php

Evolution of the mammalian brain

Two recent studies cast light on the evolution of the mammalian brain. A study of the brains of cetaceans, has found that that the cortex of a killer whale is dramatically more “folded” than that of an Amazon River dolphin (the deep and complex folding, or gyrification, of the cortex surface is what allows the human brain to have far more informational capacity than would be expected from its mass). The whales’s brain was particularly convoluted in the area of the corpus callosum, the main “bridge” between the hemispheres. In other comparative study of mammalian brains, it was found that the larger the brain, the larger the mean diameter of the axons. Axons were also less densely packed and more heavily myelinated. Across all species studied, fast cross-brain conduction times were maintained at 1-2 milliseconds.
http://gateways.bmn.com/news/story?day=031201&story=1 (BioMedNet: free registration required)

Questioning the medial temporal lobe

The medial temporal lobe includes the hippocampus, the amygdala, and the entorhinal and perirhinal cortices. It is often talked about as a single unit, but recently a prominent neurobiologist has questioned this usage. For one thing, the region didn’t evolve as one unit — the different regions arose at different times during primate evolution. Therefore, can it really be an integrated system with a common function? Her work with rhesus monkeys suggests rather that these different parts may serve cooperative and even competitive functions.
http://gateways.bmn.com/conferences/list/view?rp=2003-SFN-4-S3 (BioMedNet: free registration required)

Enzyme that turns fleeting experience into lasting memory

“Facts” may require lots of learning to impress themselves on our brain, but some events we remember effortlessly for a long time, despite only occurring once. What distinguishes those memories that are impressed so easily, without repetition? Well, using as a model for this phenomenon the apparent ability of female mice to remember for a long time the scent of a male after one mating, a mouse study suggests that emotion plays a key role, through the release of norepinephrine, a brain chemical closely related to adrenaline. Just how norepinephrine leads to strong memory formation is still unknown, but it seems that the enzyme known as protein kinase C plays a key role.
http://www.eurekalert.org/pub_releases/2003-11/wfub-rie110703.php

Rat study indicates dangers of stress during adolescence

A rat study has found that rats exposed to stress during adolescence had lower levels as adults of synaptophysin, a key protein in the hippocampus. Usually, in humans, synaptophysin levels peak between the ages of 18 and 20. The stressed rats in the study didn’t experience this usual rise in synaptophysin level. "These data may suggest why early traumatic stress, such as physical or sexual abuse or neglect, is associated with a decrease in the size of the hippocampus in adulthood."
http://www.eurekalert.org/pub_releases/2003-11/sfn-smm110803.php

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