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Learning Brain Cells Identified

[NEWS] 11-26-99

.c The Associated Press

WASHINGTON (AP) - In a finding that could lead to new treatments for Parkinson's disease, researchers report that there's a dramatic change in the brain as the mind learns new habits of behavior.

As rats learned while running in a maze, there was a change in the firing pattern of certain neurons in the brain - a new pattern that can mark the way habits are acquired, according to a study appearing today in the journal Science.

``We have made one small step toward figuring out what the brain does when we develop a habit,'' said Ann M. Graybiel, a brain researcher at Massachusetts Institute of Technology and senior author of the study.

Graybiel said just how the brain reacts as it acquires a habit of behavior is a complex process. Discovering how that process works, she said, may help researchers find new treatments for Parkinson's disease and for bad habits that affect behavior.

Parkinson's disease is a degenerative neurological disorder that destroys brain cells that produce a chemical important for movement. Symptoms include muscle stiffening, tremors and difficulty moving.

``Habits are hard to make and they are hard to break,'' Graybiel said. ``The brain mechanisms that do this are special. They are different from the brain mechanisms that let us learn a phone number. We want to find out what that special mechanism is.''

In the study, Graybiel and her colleagues implanted sensors into rats' brains. The sensors were placed in the striatum, a part of the brain involved in Parkinson's disease and in the formation of habits in people.

The sensors detected the rate of activity of brain neurons and sent signals to a computer. The sensors monitored thousands of brain cells at the same time; the computer recorded the rate of signal firing.

The rats then were taught to run a T-shaped maze. They were released at bottom of the T and then ran toward the top. The objective: find a food treat in either the right or left end of the T's cross arm. An audible clue, with one tone for left and one for right, was sounded as the rats ran through the maze.

The goal was for the rats to follow the tonal cue and turn either left or right.

Graybiel said that when the rats were just starting to learn the maze, most of the neurons firing in the brains occurred when the rats made their turn. But as the rats became maze veterans, the pattern shifted. Most of the neurons were firing at the beginning and at the end of the exercise.

``It was as if the animals learned how to anticipate'' that if they just ran the maze, they would get rewarded with food, said Graybiel.

She said her research team now is wiring other parts of the brain to discover if there is a network of neuronal activity linked to exercising a habit.

``The question is do we use a piece of brain to learn a habit and then another part of the brain to exercise that habit,'' said Graybiel. ``There may be a whole network and different parts of the network may be more active after the habit is learned.''

Eventually, she said, what is learned about how the brain acquires habits may help science find drugs or other therapies for disorders that affect areas of the brain where habits are formed. Such therapies could be useful in treating Parkinson's disease or in helping people control habits that cause destructive behavior, she said.

AP-NY-11-26-99 0143EST

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