working memory

Compound in celery, peppers reduces age-related memory deficits

November, 2010

One precursor of age-related cognitive impairment and dementia is inflammation. Research suggests why that might be, and explains why the plant nutrient luteolin can help fight memory impairment.

Inflammation in the brain appears to be a key contributor to age-related memory problems, and it may be that this has to do with the dysregulation of microglia that, previous research has shown, occurs with age. As these specialized support cells in the brain do normally when there’s an infection, with age microglia start to produce excessive cytokines, some of which result in the typical behaviors that accompany illness (sleepiness, appetite loss, cognitive deficits and depression).

Now new cell and mouse studies suggests that the flavenoid luteolin, known to have anti-inflammatory properties, apparently has these benefits because it acts directly on the microglial cells to reduce their production of inflammatory cytokines. It was found that although microglia exposed to a bacterial toxin produced inflammatory cytokines that killed neurons, if the microglia were first exposed to luteolin, the neurons lived. Exposing the neuron to luteolin had no effect.

Old mice fed a luteolin-supplemented diet for four weeks did better on a working memory test than old mice on an ordinary diet, and restored levels of inflammatory cytokines in their brains to that of younger mice.

Luteolin is found in many plants, including carrots, peppers, celery, olive oil, peppermint, rosemary and chamomile.

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Friends, family detect early Alzheimer's signs better than traditional tests

October, 2010

Cognitive tests only test you at a particular moment in time; early signs of Alzheimer's are more evident in declines in everyday behavior that are most visible to other people.

Confirming earlier research, a study involving 257 older adults (average age 75) has found that a two-minute questionnaire filled out by a close friend or family member is more accurate that standard cognitive tests in detecting early signs of Alzheimer’s.

The AD8 asks questions about changes in everyday activities:

  • Problems with judgment, such as bad financial decisions;
  • Reduced interest in hobbies and other activities;
  • Repeating of questions, stories or statements;
  • Trouble learning how to use a tool or appliance, such as a television remote control or a microwave;
  • Forgetting the month or year;
  • Difficulty handling complicated financial affairs, such as balancing a checkbook;
  • Difficulty remembering appointments; and
  • Consistent problems with thinking and memory.

Problems with two or more of these are grounds for further evaluation. The study found those with AD8 scores of 2 or more were very significantly more likely to have early biomarkers of Alzheimer’s (abnormal Pittsburgh compound B binding and cerebrospinal fluid biomarkers), and was better at detecting early stages of dementia than the MMSE. The AD8 has now been validated in several languages and is used in clinics around the world.

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Natural scenes have positive impact on brain

October, 2010

Images of nature have been found to improve attention. A new study shows that natural scenes encourage different brain regions to synchronize.

A couple of years ago I reported on a finding that walking in the park, and (most surprisingly) simply looking at photos of natural scenes, could improve memory and concentration (see below). Now a new study helps explain why. The study examined brain activity while 12 male participants (average age 22) looked at images of tranquil beach scenes and non-tranquil motorway scenes. On half the presentations they concurrently listened to the same sound associated with both scenes (waves breaking on a beach and traffic moving on a motorway produce a similar sound, perceived as a constant roar).

Intriguingly, the natural, tranquil scenes produced significantly greater effective connectivity between the auditory cortex and medial prefrontal cortex, and between the auditory cortex and posterior cingulate gyrus, temporoparietal cortex and thalamus. It’s of particular interest that this is an example of visual input affecting connectivity of the auditory cortex, in the presence of identical auditory input (which was the focus of the research). But of course the take-home message for us is that the benefits of natural scenes for memory and attention have been supported.

Previous study:

Many of us who work indoors are familiar with the benefits of a walk in the fresh air, but a new study gives new insight into why, and how, it works. In two experiments, researchers found memory performance and attention spans improved by 20% after people spent an hour interacting with nature. The intriguing finding was that this effect was achieved not only by walking in the botanical gardens (versus walking along main streets of Ann Arbor), but also by looking at photos of nature (versus looking at photos of urban settings). The findings are consistent with a theory that natural environments are better at restoring attention abilities, because they provide a more coherent pattern of stimulation that requires less effort, as opposed to urban environments that are provide complex and often confusing stimulation that captures attention dramatically and requires directed attention (e.g., to avoid being hit by a car).

Reference: 

[1867] Hunter, M. D., Eickhoff S. B., Pheasant R. J., Douglas M. J., Watts G. R., Farrow T. F. D., et al.
(2010).  The state of tranquility: Subjective perception is shaped by contextual modulation of auditory connectivity.
NeuroImage. 53(2), 611 - 618.

[279] Berman, M. G., Jonides J., & Kaplan S.
(2008).  The cognitive benefits of interacting with nature.
Psychological Science: A Journal of the American Psychological Society / APS. 19(12), 1207 - 1212.

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New advice on how much cognitive abilities decline with age

October, 2010

A new study suggests that inconsistencies in rate of age-related cognitive decline may be partly due to practice effects, but though decline does occur it is slower than some have estimated.

Reports on cognitive decline with age have, over the years, come out with two general findings: older adults do significantly worse than younger adults; older adults are just as good as younger adults. Part of the problem is that there are two different approaches to studying this, each with their own specific bias. You can keep testing the same group of people as they get older — the problem with this is that they get more and more practiced, which mitigates the effects of age. Or you can test different groups of people, comparing older with younger — but cohort differences (e.g., educational background) may disadvantage the older generations. There is also argument about when it starts. Some studies suggest we start declining in our 20s, others in our 60s.

One of my favorite cognitive aging researchers has now tried to find the true story using data from the Virginia Cognitive Aging Project involving nearly 3800 adults aged 18 to 97 tested on reasoning, spatial visualization, episodic memory, perceptual speed and vocabulary, with 1616 tested at least twice. This gave a nice pool for both cross-sectional and longitudinal comparison (retesting ranged from 1 to 8 years and averaged 2.5 years).

From this data, Salthouse has estimated the size of practice effects and found them to be as large as or larger than the annual cross-sectional differences, although they varied depending on the task and the participant’s age. In general the practice effect was greater for younger adults, possibly because younger people learn better.

Once the practice-related "bonus points" were removed, age trends were flattened, with much less positive changes occurring at younger ages, and slightly less negative changes occurring at older ages. This suggests that change in cognitive ability over an adult lifetime (ignoring the effects of experience) is smaller than we thought.

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More support for the benefits of walking for older brains

September, 2010

Many studies have now shown that walking helps older brains fight cognitive decline, but a new study shows that this is also associated with improved connectivity in important brain networks.

A study involving 65 older adults (59-80), who were very sedentary before the study (reporting less than two episodes of physical activity lasting 30 minutes or more in the previous six months), has found that those who joined a walking group improved their cognitive performance and the connectivity in important brain circuits after a year. However, those who joined a stretching and toning group showed no such improvement. The walking program involved three 40-minute walks at a moderate pace every week. The two affected brain circuits (the default mode network and the fronto-executive network) typically become less connected with age. It is worth emphasizing that the improvement was not evident at the first test, after six months, but only at the second 12-month test.

Interestingly, I noticed in the same journal issue a study into the long-term benefits of dancing for older adults. The study compared physical and cognitive performance of those who had engaged in amateur dancing for many years (average: 16.5 years) and those with no dancing or sporting engagement. The dancing group were overall significantly better than the other group on all tests: posture, balance, reaction time, motor behavior, cognitive performance. However, the best dancers weren’t any better than individuals in the other group; the group difference arose because none of the dancers performed poorly, while many of the other group did.

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Light shed on the cause of the most common learning disability

September, 2010

The discovery that the mutated NF1 gene inhibits working memory through too much GABA in the prefrontal cortex offers hope for an effective therapy for those with the most common learning disability.

Neurofibromatosis type 1 (NF1) is the most common cause of learning disabilities, caused by a mutation in a gene that makes a protein called neurofibromin. Mouse research has now revealed that these mutations are associated with higher levels of the inhibitory neurotransmitter GABA in the medial prefrontal cortex. Brain imaging in humans with NF1 similarly showed reduced activity in the prefrontal cortex when performing a working memory task, with the levels of activity correlating with task performance. It seems, therefore, that this type of learning disability is a result of too much GABA in the prefrontal cortex inhibiting the activity of working memory. Potentially they could be corrected with a drug that normalizes the excess GABA's effect. The researchers are currently studying the effect of the drug lovastatin on NF1 patients.

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[1688] Shilyansky, C., Karlsgodt K. H., Cummings D. M., Sidiropoulou K., Hardt M., James A. S., et al.
(2010).  Neurofibromin regulates corticostriatal inhibitory networks during working memory performance.
Proceedings of the National Academy of Sciences. 107(29), 13141 - 13146.

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Why it’s better to mix up your practice

August, 2010

New research confirms that it’s better to practice more than one skill at a time than to engage in repetitive drills of the same action, and reveals that different brain regions are involved in these two scenarios.

A new study explains why variable practice improves your memory of most skills better than practice focused on a single task. The study compared skill learning between those asked to practice one particular challenging arm movement, and those who practiced the movement with other related tasks in a variable practice structure. Using magnetic stimulation applied to different parts of the brain after training (which interferes with memory consolidation), it was found that interference to the dorsolateral prefrontal cortex, but not to the primary motor cortex, affected skill learning for those engaged in variable practice, whereas interference to the motor cortex, but not to the prefrontal cortex, affected learning in those engaged in constant practice.

These findings indicate that variable practice involves working memory (which happens in the prefrontal cortex) rather than motor memory, and that the need to re-engage with the task each time underlies the better learning produced by variable practice (which involves repeatedly switching between tasks). The experiment also helps set a time frame for this consolidation — interference four hours after training had no effect.

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Rehearsing so as not to forget

August, 2010

A new study shows that verbal rehearsal develops considerably between the ages of six and eight.

A study involving 117 six year old children and 104 eight year old children has found that the ability to preserve information in working memory begins at a much younger age than had previously been thought. Moreover the study revealed that, while any distraction between learning the words and having to recall them hindered recall, having to perform a verbal task was particularly damaging. This suggests that their remembering was based on “phonological rehearsal”, that is, verbally repeating the names of the items to themselves. Consistent with the research suggesting children begin to phonologically rehearse at around 7 years of age, the verbal task hindered the 8 year olds more than the 6 year olds.

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Brain fitness program produces working memory improvement in older adults

August, 2010

A new study shows improvement in visual working memory in older adults following ten hours training with a commercial brain training program. The performance gains correlated with changes in brain activity.

While brain training programs can certainly improve your ability to do the task you’re practicing, there has been little evidence that this transfers to other tasks. In particular, the holy grail has been very broad transfer, through improvement in working memory. While there has been some evidence of this in pilot programs for children with ADHD, a new study is the first to show such improvement in older adults using a commercial brain training program.

A study involving 30 healthy adults aged 60 to 89 has demonstrated that ten hours of training on a computer game designed to boost visual perception improved perceptual abilities significantly, and also increased the accuracy of their visual working memory to the level of younger adults. There was a direct link between improved performance and changes in brain activity in the visual association cortex.

The computer game was one of those developed by Posit Science. Memory improvement was measured about one week after the end of training. The improvement did not, however, withstand multi-tasking, which is a particular problem for older adults. The participants, half of whom underwent the training, were college educated. The training challenged players to discriminate between two different shapes of sine waves (S-shaped patterns) moving across the screen. The memory test (which was performed before and after training) involved watching dots move across the screen, followed by a short delay and then re-testing for the memory of the exact direction the dots had moved.

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Negative stereotypes affect learning, not just performance

August, 2010

Following on from several studies showing that being reminded of a negative stereotype for your group (be it race or gender) affects your test performance, a new study shows it also impairs learning.

A number of studies have demonstrated that negative stereotypes (such as “women are bad at math”) can impair performance in tests. Now a new study shows that this effect extends to learning. The study involved learning to recognize target Chinese characters among sets of two or four. Women who were reminded of the negative stereotypes involving women's math and visual processing ability failed to improve at this search task, while women who were not reminded of the stereotype got faster with practice. When participants were later asked to choose which of two colored squares, imprinted with irrelevant Chinese characters, was more saturated, those in the control group were slower to respond when one of the characters had been a target. However, those trained under stereotype threat showed no such effect, indicating that they had not learned to automatically attend to a target. It’s suggested that the women in the stereotype threat group tried too hard to overcome the negative stereotype, expending more effort but in an unproductive manner.

There are two problems here, it seems. The first is that people under stereotype threat have more invested in disproving the stereotype, and their efforts may be counterproductive. The second, that they are distracted by the stereotype (which uses up some of their precious working memory).

Reference: 

[1686] Rydell, R. J., Shiffrin R. M., Boucher K. L., Van Loo K., & Rydell M. T.
(2010).  Stereotype threat prevents perceptual learning.
Proceedings of the National Academy of Sciences.

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