RENEE MONTAGNE, Host:
And brain stimulation is more than just a new way to treat mental disorders. As NPR's Jon Hamilton reports, it provides a way to actually probe tiny areas of the brain to find out what they do.
JON HAMILTON: Pictures of the human brain can tell you a lot. But Alvaro Pascual Leone of Harvard Medical School says pictures alone aren't enough.
ALVARO PASCUAL: The only way we are able to really disentangle the functions of this very complicated organ is by tapping here or there and being able to find out not just what the consequences are, but perhaps even more intriguing, how the rest of the brain is coping with that disruption.
HAMILTON: Transcranial magnetic stimulation gives researchers two different ways to tap on parts of the brain. One is by using an electromagnetic frequency that temporarily disables brain cells. Eric Wassermann runs a brain stimulation unit at the National Institutes of Health. He says researchers there suspected they had found an area of the brain that was essential to speech. But they didn't know for sure until they used stimulation on volunteers to disable that part of the brain.
ERIC WASSERMANN: Suddenly, speech would become garbled and stop. And when the simulation was turned off, speech would resume suddenly. It's very dramatic. I've had it done to me, and it's a strange sensation.
HAMILTON: Wassermann says that by using a different frequency, electromagnetic stimulation can also make brain cells work better.
WASSERMANN: It's a little analogous to the enhancing effects of certain drugs, like amphetamine or methylphenidate.
HAMILTON: Which are used to treat attention deficit disorder. But Wassermann says these drugs tend to affect the entire brain. Stimulation can be limited to precise areas, indicating which ones improve our ability to focus. One interesting experiment with brain stimulation involved blind people reading Braille. Pascual-Leone says their brain scans show activity in places usually process information from the eyes.
PASCUAL: So the question was is this activity in the visual areas really contributing to the ability of these subjects to read?
HAMILTON: Brain scans couldn't answer that question. So Pascual-Leone tried brain stimulation.
PASCUAL: If you use (unintelligible) stimulation to block the activity in the visual areas of the brain in this congenitally blind subjects, they make more errors when reading Braille by touch.
HAMILTON: That meant the visual areas were important. To find out why, the team did another experiment. It involved waiting until just after a blind volunteer's finger touched a Braille symbol. Then Pascual-Leone blocked activity in the brain's visual area.
PASCUAL: The subject knows that they have touched the finger, but can't come up with the Braille symbol that was presented, suggesting that the activity in the visual cortex is contributing to the decoding of the Braille symbol.
HAMILTON: Jon Hamilton, NPR News.
MONTAGNE: In last week's Your Health, we put your questions on sleep to an expert, and you can find some answers at npr.org/yourhealth.
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