Focus-switching all in the genes

By SANJIDA O'CONNELL

Men are notoriously bad at it. Women are not only good at it, they have to excel at it if they want to juggle jobs, babies and going to wine bars.

It is multi-tasking, but for those of us who cannot walk, talk and chew gum at the same time, it may be of some comfort to know that scientists have found a gene involved in switching our attention.

It seems that some of us - men in particular - probably haven't got an efficient version of this gene, and so languish in indecision and lack of concentration.

To suggest that such abilities have a genetic component is controversial.

Dr Adele Diamond, the director of the Centre for Developmental Cognitive Neuroscience at the University of Massachusetts Medical School, and her colleagues have, nevertheless, uncovered the genetics underpinning the ability to switch our focus.

The research might eventually result in new drugs aimed at improving the lives of children who are seriously affected by an inability to pay attention.

All young children show a classic inability to switch their attention. Children can sort objects - such as a red tractor or a blue star - by colour or shape, but they cannot do both. Having sorted the star into the blue pile, they cannot put it in the star-shaped pile.

Children of 3 can tell you what the rule is, but they cannot follow their advice.

"It's not enough to know something or to remember it, you have to get that knowledge into your behaviour," says Dr Diamond.

Psychologists call it attention inertia; adults with damage to the frontal lobe of the brain suffer a similar inability.

Unlike these adults, children can be made to follow the rules correctly.

Instead of the experimenter labelling the star as blue or star-shaped, the child labels it. It is as if making the children label the object automatically refocuses their attention.

"When the adult does it, it goes in one ear and out the other," says Dr Diamond, adding that this is why we must not blame young children for their incapacity to follow adult rules of behaviour.

So that she could look at how attention inertia develops throughout childhood, Dr Diamond had the task of devising a test which could be performed by 4-year-olds as easily as 40-year-olds. The idea was that it would elicit attention inertia while still allowing volunteers to improve their performance.

The test, called a Stroop task by psychologists, consisted of a bar with a striped or a coloured button on either its right- or left-hand side; volunteers had to push either side of the bar.

In one version of the test, if the striped dot was on the left, they had to push left; if the coloured dot was on the left, they had to push right. In the second version, the buttons were on the right-hand side.

If it was a striped button, they had to push right (the opposite of the previous task); and if it was the coloured button, push left.

Both versions are straightforward, but the complication arises when one has to alternate between the two tasks. "What is hard is to flip back and forth between the two rules."

All age groups have difficulty with this task but can improve with practice; adults improve faster than children.

Using brain scans, Dr Diamond was able to show that the frontal lobes of the brain, specifically an area called the dorso-ventral prefrontal cortex, are used to perform this task.

She then wanted to find out how genes can affect our ability to focus and switch attention. Her subjects were children suffering from the genetic disorder phenylketonuria (PKU).

People with PKU are unable to switch their attention. If untreated, they are severely socially, emotionally and intellectually retarded. They have traits similar to attention-deficit hyperactive disorder (ADHD), and are sometimes misdiagnosed with it.

In fact, the drug Ritalin, used to treat ADHD, can also help ameliorate PKU in conjunction with other therapies.

Dr Diamond chose to study PKU children because if they are treated they can lead relatively normal lives with little or no cognitive impairment other than attention inertia.

Her research could thus shed light on specific processes taking place in the prefrontal cortex, as well as lead to a drug that could be used to treat sufferers.



Dr Diamond gave the children six kinds of tests. As she predicted, the children were significantly worse at tests that required the prefrontal cortex.

This is because they have low levels of tyrosine, and thus low levels of dopamine. But because the prefrontal cortex is acutely sensitive to dopamine levels, other areas of their brain are not affected.

However, children with PKU were able to do one test requiring the prefrontal cortex, namely self-ordered pointing.

The children had to point to eight pictures in a computer grid, one after the other, never pointing to the same one twice.

The pictures were then shown to the children in a different configuration, and they had to remember in which order they had pointed to them. Because the pictures had been re-ordered, they couldn't use spatial clues. "These results were completely unexpected," says Dr Diamond.

Her results were confirmed by an unexpected source. Trevor Robbins and Angela Roberts, from Cambridge University, carried out the same tests on marmoset monkeys.

They found that when the marmosets were deprived of dopamine, they were able to carry out the pointing task, but were unable to complete other tests - like the Stroop test - that needed dopamine and the prefrontal cortex.

It was still a conundrum, one Dr Diamond could not solve until last year when she attended a brain conference. Dr Daniel Weinberger, the director of the Clinical Brain Disorder Centre at the National Institutes of Health, Maryland, gave a talk on the COMT gene and how it affected dopamine levels in adults.

As Dr Weinberger explained, the COMT gene codes for an enzyme that breaks down dopamine and removes it from the brain.

Again, the prefrontal cortex has special properties: it is highly reliant on COMT because there is a paucity of molecules that transport dopamine in this region.

The COMT gene comes in two versions, a normal one and a mutation.

Dr Diamond gave her Stroop test and the self-ordered pointing test to two groups of children: those with the normal COMT gene, and those with the mutation.

She discovered that those with the mutation, like the dopamine-deprived marmosets and the PKU children, were able to carry out the self-ordered pointing task, but were impaired on the Stroop test.

On the other hand, those with the normal version were not only able to do the self-ordered pointing, they were better at switching their attention.

This, then, was the answer. The children with PKU could do the self-ordered pointing task since it did not rely on dopamine production, but they did not have efficient-enough mechanisms for generating and transporting dopamine to and within the brain to help them switch their attention.

As for the alleged differences in multi-tasking abilities between the sexes, Dr Diamond remains cautious. "I can believe women are better than men. I just don't have the data to prove it."

- INDEPENDENT

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