29 October 2009

Bad driving may be genetic

by Kate Melville

UC Irvine neuroscientists have found that people with a particular gene variant performed more than 20 percent worse on a driving test than people without it. Disturbingly, about 30 percent of the North American population has the variant. "These people make more errors from the get-go, and they forget more of what they learned after time away," lamented Dr. Steven Cramer, senior author of the study.

The variant limits the availability of a protein called brain-derived neurotrophic factor (BDNF) during activity. BDNF helps keep memories strong by supporting communication among brain cells and keeping them functioning optimally. When a person is engaged in a particular task, BDNF is secreted in the brain area connected with that activity to help the body respond. Previous studies have shown that in people with the variant, a smaller portion of the brain is stimulated when doing a task than in those with a normal BDNF gene.

"We wanted to study motor behavior, something more complex than finger-tapping," explained co-researcher Stephanie McHughen. "Driving seemed like a good choice because it has a learning curve and it's something most people know how to do."

The test was taken by 29 people - 22 without the gene variant and seven with it. They were asked to drive 15 laps on a simulator that required them to learn the nuances of a track programmed to have difficult curves and turns. Researchers recorded how well they stayed on the course over time. Four days later, the test was repeated. The results showed that people with the variant did worse on both tests than the other participants, and they remembered less the second time.

But it's not all bad news. Studies have found that people with the variant maintain their usual mental sharpness longer than those without it when neurodegenerative diseases such as Parkinson's, Huntington's and multiple sclerosis are present.

"It's as if nature is trying to determine the best approach," Cramer said. "If you want to learn a new skill or have had a stroke and need to regenerate brain cells, there's evidence that having the variant is not good. But if you've got a disease that affects cognitive function, there's evidence it can act in your favor. The variant brings a different balance between flexibility and stability."

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Source: University of California, Irvine