Put on a pair of headphones and turn up the volume so that you can’t even hear yourself speak. For those who stutter, 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—as was recently portrayed in the movie The King’s Speech. 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.
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 a related vein, The King’s Speech also mentioned the common belief that people who stutter are often left-handed, but studies have found
no such link.)
In the new study, published in the September issue of Cortex, researchers found that the unusual neural organization underlying a stutter also includes motor tasks completely unrelated to speech. A group of 30 adults, half of whom stuttered and half of whom did not, tapped a finger in time to a metronome. When the scientists interfered with the function of their left hemisphere using transcranial magnetic stimulation, a noninvasive technique that temporarily dampens brain activity, nonstutterers found themselves unable to tap in time—but those who stuttered were unaffected. When the researchers interfered with the right hemisphere, the results were reversed: the stuttering group was impaired, and the nonstutterers were fine.
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.
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Add CommentHow interesting! Just learning more and more about stuttering helps tremendously. This should also help parents who think they might have caused their child to stutter. The Stuttering Foundation with their online videos and marvelous books have been a great help to me. Parents can get help in many ways from their site, too.
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Reply | Report Abuse | Link to thisCould a young child (~3yo) possibly with apraxia have a left vs right hemisphere problem similar to the problems of a stutter?
A 'common belief' I had heard that is similar to lefthanders and stuttering is 'when a natural lefthander is switched to righthandedness he is more inclined to developing a speech problem'. I am not aware of any studies for this population, but could the change of dominant handedness go back to a right vs. left hemisphere confusion?
Glad you mentioned the Stuttering Foundation, Gloria. They have a DVD of Martin Sommer "Neurophysiology of Stuttering."
Reply | Report Abuse | Link to thisI would like to question the reasoning for stammer free speech being due to not hearing one's own voice. Is it possible that the injected sound acts like a carrier wave to aid a person's speech process,it acts like a vibratory oil which frees up the cogs of the speech mechanism.I relate this to singing,once the vocal chords are vibrating the words flow.A similar affect applies when talking as a group, your speech sits on a transmitted wave of sound and talking isn't a problem. Also in my case,when I stammer, I feel a kind of deafness and I have to fight to get over it.After a speech course in Scotland I found that telephoning became easier because I became aware of my own voice and used it to keep the speech flowing from the reflected vibration.I see a stammerer as a person with a damped vocal system which needs a stimulus, an injection of sound/vibration. A hearing aid device which gives immediate,not delayed stimulus could possibly do this.
Reply | Report Abuse | Link to thisThe Stuttering Foundation (www.stutteringhelp.org) has a DVD with Dr. Martin Sommer. Very interesting stuff. The Stuttering Foundation website has a fascinating list of famous people who stutter, as well as a "Celebrity Corner" section with in-depth articles on some of these famous people. Some of the people profiled in the articles come from families with strong histories of stuttering that give credence to the genetic basis for the speech problem. One article is on author Lewis Carroll, who came from a family of eleven kids, nine of whom stuttered past childhood. Another is about Dominick Dunne and John Gregory Dunne, brothers who were famous writers. They had an additional brother who stuttered. For so long there has been compelling evidence for the causes of stuttering pointing in the directions of neurological and genetic factors. This article was a joy to read.
Reply | Report Abuse | Link to thisBy the way, the website of The Stuttering Foundation provides many free resources to children, adults and parents.
Interesting. As a child I stuttered, and worked to overcome it. Including going into drama club and acting in school plays. Having "grown out" of stuttering, I wonder if there may be an element of neurological growth or maturation gone wrong in the brains os stutterers, as opposed to a "defect"?
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