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Thursday, December 21, 2006

Practice doesn't make perfect: new US study

Endless hours spent perfecting your golf swing or basketball shot could be a waste of time, according to a US study which has found that practice doesn't always make perfect.

Researchers at Stanford University looking at the way the brain plans and calculates motion made the discovery after training macaque monkeys to repeat a simple reaching task thousands of times.

"The nervous system was not designed to do the same thing over and over again," said Mark Churchland, postdoctoral researcher in electrical engineering and lead author of the study published Wednesday.

In the study, scientists rewarded the monkeys for reaching out to touch a coloured spot of light at different speeds.

During the exercise, scientists monitored the promoter cortex of the monkeys' brains, responsible for movement planning, and tracked the speed of the resulting motion. Over the course of thousands of reaches, the monkeys rarely moved with the exact same speed.

Small variations in reach speed followed small variations in brain activity during movement planning, before the monkeys started reaching for the spot, according to the study, published in the journal Neuron.

Contrary to conventional wisdom that movement variability is caused by muscle activity, the scientists found that neural activity accounts for about half the variations.

In other words, training muscles to perform a certain way through practice, such as countless hours teeing off or shooting a basketball, won't produce the same shot every time because the brain's behaviour is inconsistent.

After an initial training period, the monkeys' reach accuracy did not improve over time, suggesting that lots of practice can only improve movement control so much, said Krishna Shenoy, assistant professor of electrical engineering and neurosciences at Stanford University.

The researchers speculate that humans and animals evolved with this "improvisational style" in response to the predator-prey dynamic where predators never catch and kill prey in exactly the same conditions.

"Premium athletes' quest for consistency is a stark contrast to the way we evolved through history," Shenoy said.

Understanding the way the brain controls movement can help lead to treatments for neurological conditions such as Parkinson's disease, Shenoy said.

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