The Multi-Tasking Brain

Over the years, scientists have worked like the dickens to figure out which parts of the brain are responsible for sundry tasks--such as feeling sensations in the fingers, rolling one’s eyes or moving one’s feet. It has allowed them to put together a kind of map of the brain, marking out areas used for sensing or moving different body regions.

For instance, each finger gets a patch in the brain. Each whisker in a rat gets its own patch of brain.

You might imagine that the brain would keep this map neatly in place, and scientists once viewed the brain as pretty static. Now they know better. In fact, the brain is constantly on the move--forging and strengthening or weakening and breaking connections.

Makes sense when you think about it: The workings of our brains boil down to connections between nerves. Unless connections change, how can we learn, remember and forget?

One thing that happens is the boundaries of areas responsible for moving or sensing different tissues can expand, shrink, or even be taken over for sensing and moving other nearby body parts. “Takeovers” occur when regions fall into disuse--say, when someone suffers a stroke or has a limb amputated or when a whisker or limb of an animal is removed or its nerves disconnected from the brain.

What happens? For a while, a part of the brain used for sensing and moving that body part has nothing to do. Just sits there. But, over time, that region is put to work again--sensing or directing movement for another, nearby body part. A whisker is gone--and now the “whisker” region makes a limb move. A finger is gone--and now the region that senses the finger senses touch from the next finger over.

This is more than pretty amazing: It’s important when someone has a stroke, says Kimberle Jacobs, a Stanford University researcher who’s studied brain plasticity. “People do recover information when they’ve had a stroke and lost a fair amount of brain tissue--you can see one body part won’t be working but some time later can recover,” she says. “Other brain tissues can take over another function.”

Some scientists even think that such plasticity is behind “phantom” pain (or sensations such as tingles and itches) from amputated limbs. Pain feels as if it’s coming from a leg that’s no longer there. In fact, the pain is coming from elsewhere, like the face.

But nothing drastic has to happen for brain maps to shift. Play the violin and the map for your fingers in the left, fingering hand, will expand relative to the right. Or tap out a jolly rhythm on your desk. The brain region responsible for moving your fingers may expand, at least temporarily, even before your colleagues march over and tell you to give it a rest, already.

Chak-chaka-chak-chaka-chak-chaka-chaka (ohh ... macarena). I can feel my brain changing already.

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If you have an idea for a Booster Shots topic, write to Rosie Mestel at the Los Angeles Times, 202 W. 1st. St., Los Angeles, CA 90012, rosie.mestel@latimes.com.