school-age child

Air pollution impacts cognitive performance

July, 2011

A study of Michigan public schools, and a mouse study, add to growing evidence that high levels of air pollution negatively affect learning and memory.

Following several recent studies pointing to the negative effect of air pollution on children’s cognitive performance (see this April 2010 news report and this May 2011 report), a study of public schools in Michigan has found that 62.5% of the 3660 schools in the state are located in areas with high levels of industrial pollution, and those in areas with the highest industrial air pollution levels had the lowest attendance rates and the highest proportions of students who failed to meet state educational testing standards in English and math. Attendance rates are a potential indicator of health levels.

Minority students were especially hit by this — 81.5% of African American and 62.1% of Hispanic students attend schools in the top 10% of the most polluted areas, compared to 44.4% of white students.

Almost all (95%) of the industrial air pollution around schools comes from 12 chemicals (diisocyanates, manganese, sulfuric acid, nickel, chlorine, chromium, trimethylbenzene, hydrochloric acid, molybdenum trioxide, lead, cobalt and glycol ethers) that are all implicated in negative health effects, including increased risk of respiratory, cardiovascular, developmental and neurological disorders, as well as cancer.

There are potentially two issues here: the first is that air pollution causes health issues which lower school attendance and thus impacts academic performance; the other is that the pollution also directly effects the brain, thus affecting cognitive performance.

A new mouse study looking at the effects of air pollution on learning and memory has now found that male mice exposed to polluted air for six hours a day, five days a week for 10 months (nearly half their lifespan), performed significantly more poorly on learning and memory tasks than those male mice living in filtered air. They also showed more signs of anxiety- and depressive-like behaviors.

These changes in behavior and cognition were linked to clear differences in the hippocampus — those exposed to polluted air had fewer dendritic spines in parts of the hippocampus (CA1 and CA3 regions), shorter dendrites and overall reduced cell complexity. Previous mouse research has also found that such pollution causes widespread inflammation in the body, and can be linked to high blood pressure, diabetes and obesity. In the present study, the same low-grade inflammation was found in the hippocampus. The hippocampus is particularly sensitive to damage caused by inflammation.

The level of pollution the mice were exposed to was equivalent to what people may be exposed to in some polluted urban areas.

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The right sort of video game can increase your intelligence

June, 2011

Games that use the n-back task, designed to challenge working memory, may improve fluid intelligence, but only if the games are at the right level of difficulty for the individual.

It has been difficult to train individuals in such a way that they improve in general skills rather than the specific ones used in training. However, recently some success has been achieved using what is called an “n-back” task, a task that involves presenting a series of visual and/or auditory cues to a subject and asking the subject to respond if that cue has occurred, to start with, one time back. If the subject scores well, the number of times back is increased each round.

In the latest study, 62 elementary and middle school children completed a month of training on a computer program, five times a week, for 15 minutes at a time. While the active control group trained on a knowledge and vocabulary-based task, the experimental group was given a demanding spatial task in which they were presented with a sequence of images at one of six locations, one at a time, at a rate of 3s. The child had to press one key whenever the current image was at the same location as the one n items back in the series, and another key if it wasn’t. Both tasks employed themed graphics to make the task more appealing and game-like.

How far back the child needed to remember depended on their performance — if they were struggling, n would be decreased; if they were meeting the challenge, n would be increased.

Although the experimental and active control groups showed little difference on abstract reasoning tasks (reflecting fluid intelligence) at the end of the training, when the experimental group was divided into two subgroups on the basis of training gain, the story was different. Those who showed substantial improvement on the training task over the month were significantly better than the others, on the abstract reasoning task. Moreover, this improvement was maintained at follow-up testing three months later.

The key to success seems to be whether or not the games hit the “sweet spot” for the individual — fun and challenging, but not so challenging as to be frustrating. Those who showed the least improvement rated the game as more difficult, while those who improved the most found it challenging but not overwhelming.

You can try this task yourself at http://brainworkshop.sourceforge.net/.

Reference: 

Jaeggi, Susanne M, Martin Buschkuehl, John Jonides, and Priti Shah. “Short- and long-term benefits of cognitive training.” Proceedings of the National Academy of Sciences of the United States of America 2011 (June 13, 2011): 2-7. http://www.ncbi.nlm.nih.gov/pubmed/21670271.

[1183] Jaeggi, S. M., Buschkuehl M., Jonides J., & Perrig W. J.
(2008).  From the Cover: Improving fluid intelligence with training on working memory.
Proceedings of the National Academy of Sciences. 105(19), 6829 - 6833.

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Prenatal exposure to common insecticide linked to lower IQ at age 7

May, 2011

Two longitudinal studies, one rural and one urban, have reported an association between prenatal pesticide exposure and significantly lower IQ at age 7.

A study of 265 New York City minority children has found that those born with higher amounts of the insecticide chlorpyrifos had lower IQ scores at age 7. Those most exposed (top 25%) scored an average 5.3 points lower on the working memory part of the IQ test (WISC-IV), and 2.7 points lower on the full IQ test, compared to those in the lowest quartile.

The children were born prior to the 2001 ban on indoor residential use of the common household pesticide in the US. The babies' umbilical cord blood was used to measure exposure to the insecticide.

Previous research had found that, prior to the ban, chlorpyrifos was detected in all personal and indoor air samples in New York, and 70% of umbilical cord blood collected from babies. The amount of chlorpyrifos in babies' blood was associated with neurodevelopmental problems at age three. The new findings indicate that these problems persist.

While exposure to the organophosphate has measurably declined, agricultural use is still permitted in the U.S.

Similarly, another study, involving 329 7-year-old children in a farming community in California, has found that those with the highest prenatal exposure to the pesticide dialkyl phosphate (DAP) had an average IQ 7 points lower than children whose exposure was in the lowest quintile. Prenatal pesticide exposure was linked to poorer scores for working memory, processing speed, verbal comprehension, and perceptual reasoning, as well as overall IQ.

Prenatal exposure was measured by DAP concentration in the mother’s urine. Urine was also collected from the children at age 6 months and 1, 2, 3½ and 5 years. However, there was no consistent link between children’s postnatal exposure and cognition.

While this was a farming community where pesticide exposure would be expected to be high, the levels were within the range found in the general population.

It’s recommended that people wash fruit and vegetables thoroughly, and limit their use of pesticides at home.

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Exercise improves executive function and math in sedentary children

February, 2011
  • A three-month trial comparing the effects of exercise programs on cognitive function in sedentary, overweight children, has found dose-related benefits of regular aerobic exercise.

A study involving 171 sedentary, overweight 7- to 11-year-old children has found that those who participated in an exercise program improved both executive function and math achievement. The children were randomly selected either to a group that got 20 minutes of aerobic exercise in an after-school program, one that got 40 minutes of exercise in a similar program, or a group that had no exercise program. Those who got the greater amount of exercise improved more. Brain scans also revealed increased activity in the prefrontal cortex and reduced activity in the posterior parietal cortex, for those in the exercise group.

The program lasted around 13 weeks. The researchers are now investigating the effects of continuing the program for a full year. Gender, race, socioeconomic factors or parental education did not change the impact of the exercise program.

The effects are consistent with other studies involving older adults. It should be emphasized that these were sedentary, overweight children. These findings are telling us what the lack of exercise is doing to young minds. I note the report just previous, about counteracting what we have regarded as “normal” brain atrophy in older adults by the simple action of walking for 40 minutes three times a week. Children and older adults might be regarded as our canaries in the coal mine, more vulnerable to many factors that can affect the brain. We should take heed.

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Children with autism lack visual skills required for independence

February, 2011

Autism is popularly associated with intense awareness of systematic regularities, but a new study shows that the skill displayed in computer tasks is not available in real-world tasks.

Contrary to previous laboratory studies showing that children with autism often demonstrate outstanding visual search skills, new research indicates that in real-life situations, children with autism are unable to search effectively for objects. The study, involving 20 autistic children and 20 normally-developing children (aged 8-14), used a novel test room, with buttons on the floor that the children had to press to find a hidden target among multiple illuminated locations. Critically, 80% of these targets appeared on one side of the room.

Although autistics are generally believed to be more systematic, with greater sensitivity to regularities within a system, such behavior was not observed. Compared to other children, those with autism were slower to pick up on the regularities that would help them choose where to search. The slowness was not due to a lack of interest — all the children seemed to enjoy the game, and were keen to find the hidden targets.

The findings suggest that those with ASD have difficulties in applying the rules of probability to larger environments, particularly when they themselves are part of that environment.

Reference: 

[2055] Pellicano, E., Smith A. D., Cristino F., Hood B. M., Briscoe J., & Gilchrist I. D.
(2011).  Children with autism are neither systematic nor optimal foragers.
Proceedings of the National Academy of Sciences. 108(1), 421 - 426.

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Twin studies shed light on relationship among ADHD, reading, math

January, 2011

While one twin study points to the common attribute of slow processing speed between those with ADHD and those with reading disabilities, another indicates a role for environment.

A twin study involving 457 pairs has found that ADHD on its own was associated with a reduced ability to inhibit responses to stimuli, while reading disabilities were associated independently with weaknesses on measures of phoneme awareness, verbal reasoning, and working memory. Both disorders were associated with a slow processing speed, and there was a significant genetic correlation between RD and ADHD.

However, just to remind us that genetics are rarely solely the answer, another twin study, involving 271 pairs of 10-year-old identical and fraternal twins, has found evidence that the associations between ADHD symptoms, reading outcomes and math outcomes are a product of both genetic and common environmental influences. The researchers speculate that such environmental influences may include aspects of the classroom and homework environment.

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What children eat for breakfast affects brain development

January, 2011

A Japanese study finds higher IQ among children who habitually eat white rice for breakfast, compared to those who eat white bread.

A number of studies have provided evidence that eating breakfast has an immediate benefit for cognitive performance in children. Now a new study suggests some “good” breakfasts are better than others.

A Japanese study of 290 healthy, well-nourished children, has revealed that those whose breakfast staple was white rice had a significantly larger ratio of gray matter in their brains, and several significantly larger regions, including the left superior temporal gyrus and bilateral caudate. Those who habitually ate white bread had significantly larger regional gray and white matter volumes of several regions, including the orbitofrontal gyri, right precentral gyrus and postcentral gyrus. Overall IQ scores, and scores on the perceptual organization subcomponent in particular, were significantly higher for the rice group.

One possible reason for the difference may be the difference in the glycemic index (GI) of these two substances; foods with a low GI are associated with less blood-glucose fluctuation than are those with a high GI. There is also a difference in fat content, with those eating white bread typically consuming more fat than those eating a rice-based breakfast. High levels of fat have been shown to reduce the expression of BDNF.

Regardless of the reason for the difference, the fact that breakfast staple type affects brain size and cognitive function in healthy children points to the importance of good nutrition during the years of brain development.

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Computer-based program may help ADHD symptoms in children

January, 2011

A five-week training program to improve working memory has significantly improved working memory, attention, and organization in many children and adolescents with ADHD.

A working memory training program developed to help children with ADHD has been tested by 52 students, aged 7 to 17. Between a quarter and a third of the children showed significant improvement in inattention, overall number of ADHD symptoms, initiation, planning/organization, and working memory, according to parental ratings. While teacher ratings were positive, they did not quite reach significance. It is worth noting that this improvement was maintained at the four-month follow-up.

The children used the software in their homes, under the supervision of their parents and the researchers. The program includes a set of 25 exercises in a computer-game format that students had to complete within 5 to 6 weeks. For example, in one exercise a robot will speak numbers in a certain order, and the student has to click on the numbers the robot spoke, on the computer screen, in the opposite order. Each session is 30 to 40 minutes long, and the exercises become progressively harder as the students improve.

The software was developed by a Swedish company called Cogmed in conjunction with the Karolinska Institute. Earlier studies in Sweden have been promising, but this is the first study in the United States, and the first to include children on medication (60% of the participants).

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Sensory integration in autism

October, 2010

A new study provides evidence for the theory that sensory integration is impaired in autism.

Children with autism often focus intently on a single activity or feature of their environment. A study involving 17 autistic children (6-16 years) and 17 controls has compared brain activity as they watched a silent video of their choice while tones and vibrations were presented, separately and simultaneously.

A simple stimulus takes about 20 milliseconds to arrive in the brain. When information from multiple senses registers at the same time, integration takes about 100 to 200 milliseconds in normally developing children. But those with autism took an average of 310 milliseconds to integrate the noise and vibration when they occurred together. The children with autism also showed weaker signal strength, signified by lower amplitude brainwaves.

The findings are consistent with theories that automatic sensory integration is impaired in autism, and may help explain autism’s characteristic sensitivity to excessive sensory stimulation.

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Child's 'mental number line' affects memory for numbers

October, 2010

Young children’s memory for numbers reflects their understanding that numbers, however big, are all evenly spaced.

When children learn to count, they do so by rote. Understanding what the numbers really mean comes later. This is reflected in the way children draw a number line. In the beginning, they typically put more space between the smaller numbers, with the larger numbers all scrunched up at the end (a logarithmic number line). Eventually they progress to a number line where the numbers are evenly spaced (linear number line).

Now a series of experiments with preschoolers and second graders has revealed that the more linear the child's magnitude representations (as seen on the number line as well as in other tasks), the better the child was at remembering numbers (for example, from a story with some numbers included).

This was true for preschoolers for numbers from 1-20 and for elementary school children for numbers from 1-1000, and for four different number tasks measuring numerical-magnitude representations (categorization and number-line, measurement, and numerosity estimation). Other types of numerical knowledge—numeral identification and counting—were unrelated to remembering numbers.

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