If you saw the movie The King’s Speech. there was a pivotal scene where the future king was convinced to put on a pair of headphones blaring music, and when he began to speak, his voice was clear and fluent. You may have been wondering “how does that work?” For those who stutter, when the masking noise goes on, this is when the magic happens. Without the ability to hear their own voice, people with this speech impediment no longer stumble over their words. This simple trick works because of the unusual way the brain of people who stutter is organized—a neural setup that affects other actions besides speech, according to a new study.
According to Scientific American; Normal speech requires the brain to control movement of the mouth and vocal chords using the sound of the speaker’s own voice as a guide. This integration of movement and hearing typically happens in the brain’s left hemisphere, in a region of the brain known as the premotor cortex. In those who stutter, however, the process occurs in the right hemisphere—probably because of a slight defect on the left side, according to past brain-imaging studies. Singing requires a similar integration of aural input and motor control, but the processing typically occurs in the right hemisphere, which may explain why those who stutter can sing as well as anyone else.
In the new study, researchers found that the unusual neural organization underlying a stutter also includes motor tasks completely unrelated to speech. According to lead author Martin Sommer, a neuroscientist at the University of Göttingen in Germany,the results suggest that the left-hemisphere defect underlying a stutter causes trouble with sensory integration in general, rather than specifically speech-related problems as was historically thought. “Like in stroke patients, the right side seems to jump in and compensate,” Sommer explains. But that part of the brain did not evolve to handle those tasks, so problems—such as a stutter—can emerge.