anxiety

Poverty affects brain development through attention needs

December, 2012

One reason for the association between poverty and poorer cognition in children may lie in how poverty affects attention, with poor children tending to use more cognitive resources in monitoring the environment.

There have been a number of studies in the past few years showing how poverty affects brain development and function. One of these showed specifically that children of high and low socioeconomic status showed differences in brain wave patterns associated with an auditory selective attention task. This was thought to indicate that the groups were using different mechanisms to carry out the task, with the lower SES children employing extra resources to attend to irrelevant information.

In a follow-up study, 28 young adolescents (12-14 years) from two schools in neighborhoods of different socioeconomic status answered questions about their emotional and motivational state at various points during the day, and provided saliva samples to enable monitoring of cortisol levels. At one point in the afternoon, they also had their brainwaves monitored while they carried out an auditory selective attention task (hearing different sounds played simultaneously into both ears, they were required to press a button as fast as possible when they heard one particular sound).

While performance on the task was the same for both groups, there were, once again, differences in the brain wave patterns. Higher SES children exhibited far larger theta waves in the frontal lobes in response to sounds they attended to than to compared to those they should have ignored, while lower SES children showed much larger theta waves to the unattended sounds than for the attended sounds.

While the lower SES children had higher cortisol levels throughout the school day, like the higher SES children, they showed little change around the task, suggesting neither group was particularly stressed by the task. Both groups also showed similar levels of boredom and motivation.

What the findings suggest is that lower SES children have to exert more cognitive control to avoid attending to irrelevant stimuli than higher SES children — perhaps because they live in more threatening environments.

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C-sections don’t trigger key protein in brain

September, 2012

A mouse study finds that a vital protein is triggered by natural birth, and its reduction in those delivered by C-section correlates with poorer memory and greater anxiety in adulthood.

In the light of a general increase in caesarean sections, it’s somewhat alarming to read about a mouse study that found that vaginal birth triggers the expression of a protein in the brains of newborns that improves brain development, and this protein expression is impaired in the brains of those delivered by C-section.

The protein in question —mitochondrial uncoupling protein 2 (UCP2) — is important for the development of neurons and circuits in the hippocampus. Indeed, it has a wide role, being involved in regulation of fuel utilization, mitochondrial bioenergetics, cell proliferation, neuroprotection and synaptogenesis. UCP2 is induced by cellular stress.

Among the mice, natural birth triggered UCP2 expression in the hippocampus (presumably because of the stress of the birth), which was reduced in those who were born by C-section. Not only were levels of UCP2 lower in C-section newborns, they continued to be lower through to adulthood.

Cell cultures revealed that inhibiting UCP2 led to decreased number of neurons, neuron size, number of dendrites, and number of presynaptic clusters. Mice with (chemically or genetically) inhibited UCP2 also showed behavioral differences indicative of greater levels of anxiety. They explored less, and they showed poorer spatial memory.

The effects of reduced UCP2 on neural growth means that factors that encourage the growth of new synapses, such as physical exercise, are likely to be much less useful (if useful at all). Could this explain why exercise seems to have no cognitive benefits for a small minority? (I’m speculating here.)

Although the researchers don’t touch on this (naturally enough, since this was a laboratory study), I would also speculate that, if the crucial factor is stress during the birth, this finding applies only to planned C-sections, not to those which become necessary during the course of labor.

UCP2 is also a critical factor in fatty acid utilization, which has a flow-on effect for the creation of new synapses. One important characteristic of breast milk is its high content of long chain fatty acids. It’s suggested that the triggering of UCP2 by natural birth may help the transition to breastfeeding. This in turn has its own benefits for brain development.

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Rapamycin makes young mice learn better and prevents decline in old mice

July, 2012

Further evidence from mice studies that the Easter Island drug improves cognition, in young mice as well as old.

I have reported previously on research suggesting that rapamycin, a bacterial product first isolated from soil on Easter Island and used to help transplant patients prevent organ rejection, might improve learning and memory. Following on from this research, a new mouse study has extended these findings by adding rapamycin to the diet of healthy mice throughout their life span. Excitingly, it found that cognition was improved in young mice, and abolished normal cognitive decline in older mice.

Anxiety and depressive-like behavior was also reduced, and the mice’s behavior demonstrated that rapamycin was acting like an antidepressant. This effect was found across all ages.

Three "feel-good" neurotransmitters — serotonin, dopamine and norepinephrine — all showed significantly higher levels in the midbrain (but not in the hippocampus). As these neurotransmitters are involved in learning and memory as well as mood, it is suggested that this might be a factor in the improved cognition.

Other recent studies have suggested that rapamycin inhibits a pathway in the brain that interferes with memory formation and facilitates aging.

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Gender differences in effects of anxiety on performance

July, 2012

Two studies indicate that, while anxiety is present in both sexes, it only impairs performance in females.

A British study looking at possible gender differences in the effects of math anxiety involved 433 secondary school children (11-16 years old) completing customized (year appropriate) mental mathematics tests as well as questionnaires designed to assess math anxiety and (separately) test anxiety. These sources of anxiety are often confounded in research studies (and in real life!), and while they are indeed related, reported correlations are moderate, ranging from .30 to .50.

Previous research has been inconsistent as regards gender differences in math anxiety. While many studies have found significantly greater levels of math anxiety in females, many studies have found no difference, and some have even found higher levels in males. These inconsistencies may stem from differences in how math anxiety is defined or measured.

The present study looked at a rather more subtle question: does the connection between math anxiety and math performance differ by gender? Again, previous research has produced inconsistent findings.

Findings in this study were very clear: while there was no difference between boys and girls in math performance, there were marked differences in both math and test anxiety. Girls showed significantly greater levels of both. Both boys and girls showed a positive correlation between math anxiety and test anxiety, and a negative correlation between math anxiety and math performance, and test anxiety and performance. However, these relationships between anxiety and performance were stronger for girls than boys, with the correlation between test anxiety and performance being only marginally significant for boys (p<0.07), and the correlation between math anxiety and performance disappearing once test anxiety was controlled for.

In other words, greater math anxiety was linked to poorer math performance, but it was significant only for girls. Moreover, anxiety experienced by boys may simply reflect test anxiety, rather than specific math anxiety.

It is worth emphasizing that there was no gender difference in performance — that is, despite laboring under the burden of greater levels of anxiety, the girls did just as well as boys. This suggests that girls might do better than boys if they were free of anxiety. It is possible, however, that levels of anxiety didn’t actually differ between boys and girls — that the apparent difference stems from girls feeling more free to express their anxiety.

However, the finding that anxiety is greater in girls than boys is in line with evidence that anxiety (and worry in particular) is twice as prevalent in women as men, and more support for the idea that the girls are under-performing because of their anxiety comes from another recent study.

In this study, 149 college students performed a relatively simple task while their brain activity was measured. Specifically, they had to identify the middle letter in a series of five-letter groups. Sometimes the middle letter was the same as the other four ("FFFFF") while sometimes it was different ("EEFEE"). Afterward the students completed questionnaires about their anxiety and how much they worry (Penn State Worry Questionnaire and the Anxious Arousal subscale of the Mood and Anxiety Symptom Questionnaire).

Anxiety scores were significantly negatively correlated with accuracy on the task; worry scores were unrelated to performance.

Only girls who identified themselves as particularly anxious or big worriers recorded high brain activity when they made mistakes during the task (reflecting greater performance-monitoring). Although these women performed about the same as others on simple portions of the task, their brains had to work harder at it. Then, as the test became more difficult, the anxious females performed worse, suggesting worrying got in the way of completing the task.

Greater performance monitoring was not evident among anxious men.

[A reminder: these are group differences, and don't mean that all men or all women react in these ways.]

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How exercise affects the brain, and who it benefits

June, 2012

New research indicates that the cognitive benefits of exercise depend on the gene variant you carry.

I’ve mentioned before that, for some few people, exercise doesn’t seem to have a benefit, and the benefits of exercise for fighting age-related cognitive decline may not apply to those carrying the Alzheimer’s gene.

New research suggests there is another gene variant that may impact on exercise’s effects. The new study follows on from earlier research that found that physical exercise during adolescence had more durable effects on object memory and BDNF levels than exercise during adulthood. In this study, 54 healthy but sedentary young adults (aged 18-36) were given an object recognition test before participating in either (a) a 4-week exercise program, with exercise on the final test day, (b) a 4-week exercise program, without exercise on the final test day, (c) a single bout of exercise on the final test day, or (d) remaining sedentary between test days.

Exercise both improved object recognition memory and reduced perceived stress — but only in one group: those who exercised for 4 weeks including the final day of testing. In other words, both regular exercise and recent exercise was needed to produce a memory benefit.

But there is one more factor — and this is where it gets really interesting — the benefit in this group didn’t happen for every member of the group. Only those carrying a specific genotype benefited from regular and recent exercise. This genotype has to do with the brain protein BDNF, which is involved in neurogenesis and synaptic plasticity, and which is increased by exercise. The BDNF gene comes in two flavors: Val and Met. Previous research has linked the less common Met variant to poorer memory and greater age-related cognitive decline.

In other words, it seems that the Met allele affects how much BDNF is released as a result of exercise, and this in turn affects cognitive benefits.

The object recognition test involved participants seeing a series of 50 images (previously selected as being highly recognizable and nameable), followed by a 15 minute filler task, before seeing 100 images (the previous 50 and 50 new images) and indicating which had been seen previously. The filler task involved surveys for state anxiety, perceived stress, and mood. On the first (pre-program) visit, a survey for trait anxiety was also completed.

Of the 54 participants, 31 carried two copies of the Val allele, and 23 had at least one Met allele (19 Val/Met; 4 Met/Met). The population frequency for carrying at least one Met allele is 50% for Asians, 30% in Caucasians, and 4% in African-Americans.

Although exercise decreased stress and increased positive mood, the cognitive benefits of exercise were not associated with mood or anxiety. Neither was genotype associated with mood or anxiety. However, some studies have found an association between depression and the Met variant, and this study is of course quite small.

A final note: this study is part of research looking at the benefits of exercise for children with ADHD. The findings suggest that genotyping would enable us to predict whether an individual — a child with ADHD or an older adult at risk of cognitive decline or impairment — would benefit from this treatment strategy.

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Menopause ‘brain fog’ a product of poor sleep and depression?

May, 2012

A smallish study of women approaching and in menopause found that some experienced poorer working memory and attention, and these were more likely to have poorer sleep, depression, and anxiety.

A study involving 75 perimenopausal women aged 40 to 60 has found that those with memory complaints tended to show impairments in working memory and attention. Complaints were not, however, associated with verbal learning or memory.

Complaints were also associated with depression, anxiety, somatic complaints, and sleep disturbance. But they weren’t linked to hormone levels (although estrogen is an important hormone for learning and memory).

What this suggests to me is that a primary cause of these cognitive impairments may be poor sleep, and anxiety/depression. A few years ago, I reported on a study that found that, although women’s reports of how many hot flashes they had didn’t correlate with memory impairment, an objective measure of the number of flashes they experienced during sleep did. Sleep, as I know from personal experience, is of sufficient importance that my rule-of-thumb is: don’t bother looking for any other causes of attention and memory deficits until you have sorted out your sleep!

Having said that, depressive symptoms showed greater relationship to memory complaints than sleep disturbance.

It’s no big surprise to hear that it is working memory in particular that is affected, because what many women at this time of life complain of is ‘brain fog’ — the feeling that your brain is full of cotton-wool. This doesn’t mean that you can’t learn new information, or remember old information. But it does mean that these tasks will be impeded to the extent that you need to hold on to too many bits of information. So mental arithmetic might be more difficult, or understanding complex sentences, or coping with unexpected disruptions to your routine, or concentrating on a task for a long time.

These sorts of problems are typical of those produced by on-going sleep deprivation, stress, and depression.

One caveat to the findings is that the study participants tended to be of above-average intelligence and education. This would protect them to a certain extent from cognitive decline — those with less cognitive reserve might display wider impairment. Other studies have found verbal memory, and processing speed, impaired during menopause.

Note, too, that a long-running, large population study has found no evidence for a decline in working memory, or processing speed, in women as they pass through perimenopause and menopause.

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Pycnogenol improves cognition in college students in small trial

March, 2012

Another small study indicates that the plant extract Pycnogenol may improve working memory.

Back in 2008, I reported on a small study that found that daily doses of Pycnogenol® for three months improved working memory in older adults, and noted research indicating that the extract from the bark of the French maritime pine tree had reduced symptoms in children with ADHD. Now another study, involving 53 Italian university students, has found that cognitive performance improved in those taking 100 mg of Pycnogenol every day for eight weeks.

Students taking the supplement had higher scores on university exams than the control group, and they were apparently happier, less anxious, and more alert. It seems plausible that the improvement in academic performance results from working memory benefits.

The plant extract is an antioxidant, and benefits may have something to do with improved vascular function and blood flow in the brain.

However, the control group was apparently not given a placebo (I’m relying on the abstract and press release here, as this journal is not one to which I have access), they were simply “a group of equivalent students”. I cannot fathom why a double-blind, placebo procedure wasn’t followed, and it greatly lessens the conclusions of this study. Indeed, I wouldn’t ordinarily report on it, except that I have previously reported on this dietary supplement, and I am in hopes that a better study will come along. In the meantime, this is another small step, to which I wouldn’t give undue weight.

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Luzzi R., Belcaro G., Zulli C., Cesarone M. R., Cornelli U., Dugall M., Hosoi M., Feragalli B. 2011. Pycnogenol® supplementation improves cognitive function, attention and mental performance in students. Panminerva Medica, 53(3 Suppl 1), 75-82.

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Negative stereotypes about aging affect how well older adults remember

March, 2012

Another study has come out supporting the idea that negative stereotypes about aging and memory affect how well older adults remember. In this case, older adults reminded of age-related decline were more likely to make memory errors.

In the study, 64 older adults (60-74; average 70) and 64 college students were compared on a word recognition task. Both groups first took a vocabulary test, on which they performed similarly. They were then presented with 12 lists of 15 semantically related words. For example, one list could have words associated with "sleep," such as "bed," "rest," "awake," "tired" and "night" — but not the word “sleep”. They were not told they would be tested on their memory of these, rather they were asked to rate each word for pleasantness.

They then engaged in a five-minute filler task (a Sudoku) before a short text was read to them. For some, the text had to do with age-related declines in memory. These participants were told the experiment had to do with memory. For others, the text concerned language-processing research. These were told the experiment had to do with language processing and verbal ability.

They were then given a recognition test containing 36 of the studied words, 48 words unrelated to the studied words, and 12 words related to the studied words (e.g. “sleep”). After recording whether or not they had seen each word before, they also rated their confidence in that answer on an 8-point scale. Finally, they were given a lexical decision task to independently assess stereotype activation.

While young adults showed no effects from the stereotype manipulation, older adults were much more likely to falsely recognize related words that had not been studied if they had heard the text on memory. Those who heard the text on language were no more likely than the young adults to falsely recognize related words.

Note that there is always quite a high level of false recognition of such items: young adults, and older adults in the low-threat condition falsely recognized around half of the related lures, compared to around 10% of unrelated words. But in the high-threat condition, older adults falsely recognized 71% of the related words.

Moreover, older adults’ confidence was also affected. While young adults’ confidence in their false memories was unaffected by threat condition, older adults in the high-threat condition were more confident of their false memories than older adults in the low-threat condition.

The idea that older adults were affected by negative stereotypes about aging was supported by the results of the lexical decision task, which found that, in the high-threat condition, older adults responded more quickly to words associated with negative stereotypes than to neutral words (indicating that they were more accessible). Young adults did not show this difference.

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Thomas, A. K., & Dubois, S. J. (2011). Reducing the burden of stereotype threat eliminates age differences in memory distortion. Psychological science, 22(12), 1515-7. doi:10.1177/0956797611425932

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Group settings hurt expressions of intelligence, especially in women

March, 2012

Comparing performance on an IQ test when it is given under normal conditions and when it is given in a group situation reveals that IQ drops in a group setting, and for some (mostly women) it drops dramatically.

This is another demonstration of stereotype threat, which is also a nice demonstration of the contextual nature of intelligence. The study involved 70 volunteers (average age 25; range 18-49), who were put in groups of 5. Participants were given a baseline IQ test, on which they were given no feedback. The group then participated in a group IQ test, in which 92 multi-choice questions were presented on a monitor (both individual and group tests were taken from Cattell’s culture fair intelligence test). Each question appeared to each person at the same time, for a pre-determined time. After each question, they were provided with feedback in the form of their own relative rank within the group, and the rank of one other group member. Ranking was based on performance on the last 10 questions. Two of each group had their brain activity monitored.

Here’s the remarkable thing. If you gather together individuals on the basis of similar baseline IQ, then you can watch their IQ diverge over the course of the group IQ task, with some dropping dramatically (e.g., 17 points from a mean IQ of 126). Moreover, even those little affected still dropped some (8 points from a mean IQ of 126).

Data from the 27 brain scans (one had to be omitted for technical reasons) suggest that everyone was initially hindered by the group setting, but ‘high performers’ (those who ended up scoring above the median) managed to largely recover, while ‘low performers’ (those who ended up scoring below the median) never did.

Personality tests carried out after the group task found no significant personality differences between high and low performers, but gender was a significant variable: 10/13 high performers were male, while 11/14 low performers were female (remember, there was no difference in baseline IQ — this is not a case of men being smarter!).

There were significant differences between the high and low performers in activity in the amygdala and the right lateral prefrontal cortex. Specifically, all participants had an initial increase in amygdala activation and diminished activity in the prefrontal cortex, but by the end of the task, the high-performing group showed decreased amygdala activation and increased prefrontal cortex activation, while the low performers didn’t change. This may reflect the high performers’ greater ability to reduce their anxiety. Activity in the nucleus accumbens was similar in both groups, and consistent with the idea that the students had expectations about the relative ranking they were about to receive.

It should be pointed out that the specific feedback given — the relative ranking — was not a factor. What’s important is that it was being given at all, and the high performers were those who became less anxious as time went on, regardless of their specific ranking.

There are three big lessons here. One is that social pressure significantly depresses talent (meetings make you stupid?), and this seems to be worse when individuals perceive themselves to have a lower social rank. The second is that our ability to regulate our emotions is important, and something we should put more energy into. And the third is that we’ve got to shake ourselves loose from the idea that IQ is something we can measure in isolation. Social context matters.

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Confidence is key to women's spatial skills

March, 2012

A series of experiments has found that confidence fully accounted for women’s poorer performance on a mental rotation task.

One of the few established cognitive differences between men and women lies in spatial ability. But in recent years, this ‘fact’ has been shaken by evidence that training can close the gap between the genders. In this new study, 545 students were given a standard 3D mental rotation task, while at the same time manipulating their confidence levels.

In the first experiment, 70 students were asked to rate their confidence in each answer. They could also choose not to answer. Confidence level was significantly correlated with performance both between and within genders.

On the face of it, these findings could be explained, of course, by the ability of people to be reliable predictors of their own performance. However, the researchers claim that regression analysis shows clearly that when the effect of confidence was taken into account, gender differences were eliminated. Moreover, gender significantly predicted confidence.

But of course this is still just indicative.

In the next experiment, however, the researchers tried to reduce the effect of confidence. One group of 87 students followed the same procedure as in the first experiment (“omission” group), except they were not asked to give confidence ratings. Another group of 87 students was not permitted to miss out any questions (“commission” group). The idea here was that confidence underlay the choice of whether or not to answer a question, so while the first group should perform similarly to those in the first experiment, the second group should be less affected by their confidence level.

This is indeed what was found: men significantly outperformed women in the first condition, but didn’t in the second condition. In other words, it appears that the mere possibility of not answering makes confidence an important factor.

In the third experiment, 148 students replicated the commission condition of the second experiment with the additional benefit of being allowed unlimited time. Half of the students were required to give confidence ratings.

The advantage of unlimited time improved performance overall. More importantly, the results confirmed those produced earlier: confidence ratings produced significant gender differences; there were no gender differences in the absence of such ratings.

In the final experiment, 153 students were required to complete an intentionally difficult line judgment task, which men and women both carried out at near chance levels. They were then randomly informed that their performance had been either above average (‘high confidence’) or below average (‘low confidence’). Having manipulated their confidence, the students were then given the standard mental rotation task (omission version).

As expected (remember this is the omission procedure, where subjects could miss out answers), significant gender differences were found. But there was also a significant difference between the high and low confidence groups. That is, telling people they had performed well (or badly) on the first task affected how well they did on the second. Importantly, women in the high confidence group performed as well as men in the low confidence group.

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