Searching for the Circuitry Behind the Stutter

Stuttering caused by changes in brain circuits controlling speech production, research found.

Stuttering can range greatly in severity and sound. Some stutters barely affect their owners, while other stutters diminish their owner’s ability to communicate. New research explores the brain changes behind the stammer.

According to a press release issued by the Children’s Hospital Los Angeles (CHLA), a new study found that stuttering is caused by changes in the brain circuits that control speech production, as well as brain circuits that support attention and emotion.

This is the first study to use proton magnetic resonance spectroscopy (MRS) to look at brain regions in both adult and children stutterers. Unlike similar tests, MRS is used to study metabolic changes in the brain and provides physiological and chemical information instead of anatomy.

To conduct the study, researchers enlisted 94 participants—47 children and 47 adults. Some participants were stutterers and some were not. Using MRS, researchers analyzed the participants’ neural density in certain brain circuits and regions they suspected stuttering to affect.

They found that the affected regions included major nodes in the Bohland speech-production network (which regulates motor activity), the default mode network (which regulates attention) and the emotional-memory network (which regulates emotion).

“People with changes here are more likely to stutter and have more severe stuttering,” lead researcher Bradley S. Peterson, MD, said in the press release. “And emotions like anxiety and stress also tend to make stuttering worse, likely because this network interacts with language and attention control circuits."

Dr. Peterson is the Director of the Institute for the Developing Mind at CHLA, and Professor and Director of the Division of Child and Adolescent Psychiatry at the Keck School of Medicine at the University of Southern California.

About three million Americans stutter, according to the National Institute on Deafness and Other Communication Disorders. It occurs most often in children between the ages of two and six, 75 percent of whom outgrow it. In the remaining 25 percent, it can be a lifelong communication disorder.

Researchers believe their unique MRS study confirms that disturbances in neuronal or membrane metabolism contribute to the development of stuttering. Their findings revealed differences between adult and child stutterers, suggesting that adults and children who stutter have different metabolic profiles.

The full study was published in the Journal of the American Medical Association (JAMA).

The research was funded in part by the National Institute of Mental Health and the Children’s Hospital Los Angeles.

The authors declared no conflicts of interest.

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