Some say the problem is due to deficiencies in hearing. Others say it results from peculiarities in the areas of the brain that govern the motor functions of speech. And still others believe that the left side of the brain, which normally commands language, fails to develop its normal role. The new results show that all of these areas may play a part. Now, he says, they are beginning to see the whole beast.
PET scans track the flow of radioactively labelled blood in the brain.
Areas of high blood flow are assumed to be the most active. While the volunteers were being scanned, the researchers asked them to read aloud from a novel. Predictably, none of the controls had difficulty and all of the stutterers did. The brains of the stutterers showed unusual activity in areas associated with movement. For example, the motor areas of the cerebellum showed twice as much activity as those of normal speakers.