Brain Differences in Stuttering

There has long been disagreement about the causes of stuttering. The Stuttering Foundation of America states on its website that, "There is no reason to believe that emotional trauma causes stuttering." Additionally, the National Stuttering Association website states that, "We do know that stuttering is not caused by emotional problems and is not a 'nervous' disorder. We also know that stuttering is not the fault of the family or the person who stutters."

However, many psychologists disagree with this assessment and some still claim that psychological and other supports, such as the afterschool programs underwritten by the car donation charity Kars For Kids can make a difference. Anyone who has watched the film The King’s Speech, about King George VI’s stuttering issues sees that with emotional support stuttering can improve. Clearly, the King’s vocal coach didn’t know a thing about speech therapy. It was all about getting Bertie to vent.

But maybe that’s not the whole story, especially now that there has been hard data around for a few years now to support stuttering as a physiological disorder. A 2010 study used functional magnetic resonance imaging (fMRI) to demonstrate that those who stutter manifest abnormal brain activity even while engaged in passive activities such as reading and listening. These results suggest that people who stutter have impaired speech because of brain circuit irregularities that impact on several language processing locations and not just those devoted to speech production. The study was presented at Neuroscience 2010, a once yearly meeting of the Society for Neuroscience which took place in San Diego.

Lifelong Struggle

One in 20 children is affected by stuttering. While most grow out of this speech impairment, one out of every five children continues a lifelong struggle toward fluid speech. While no one knows the exact cause of stuttering, earlier studies have shown reduced activity in brain centers linked with listening along with increased brain activity in those areas responsible for movement and speech. The new study focused on whether this type of irregular brain activity would also be apparent during a stutterer’s silent reading.

Kate Watkins, PhD, the University of Oxford-affiliated author of this study felt that if the brain patterns during silent reading were also abnormal, this would show these anomalies to be typical for a stuttering brain and not a separate byproduct of speech production issues due to stuttering. To this end, Watkins and her colleagues used functional resonance imaging (fMRI) to compare brain activity in 12 stuttering adults with 12 adults who do not stutter.

The scans were conducted during three separate trials. During the first trial, the volunteers listened to spoken sentences. In the second trial, the participants read sentences silently. In the third and last trial, the subjects read the sentences silently as another person read the sentences aloud.

Distinct Differences

The authors discovered that the brains of those participants who stuttered showed distinct differences from the brains of the non-stutterers in each of the three tests. Only during the silent listening phase did the stutterers exhibit greater activity in auditory areas of the brain. While reading, activity in motor areas of the brain decreased, in particular that involving a circuit needed for the sequence of movement.

"Our findings likely reflect that individuals who stutter have impaired speech processing due to abnormal interactions in brain circuits," said Watkins. "In future studies, it will be important to examine changes in these brain areas in young children to find out if these interactions result from a lifetime of stuttering or point toward the cause of stuttering itself."