Stuttering is not just a nervous tic – it’s the result of low blood flow to a specific region of the brain that processes speech, according to a new study in Human Brain Mapping.
Scientists have discovered that blood flow in the speech-formulating part of the brain known as Broca’s area has a direct impact on stuttering among both adults and children, according to the study.
The researchers, affiliated with Children’s Hospital Los Angeles (CHLA), employed a novel approach to assess the brain functioning of study participants. To their knowledge, they are the first to use perfusion magnetic resonance imaging (MRI) “to investigate the differences in brain activity in persons who stutter,” they report.
The MRI results showed a clear decrease in the amount of regional cerebral blood flow in Broca’s area among those who stutter. They also discovered that when low blood flow affected other areas of the “posterior language loop” in the brain, the stuttering was worse.
“When other portions of the brain circuit related to speech were also affected according to our blood flow measurements, we saw more severe stuttering in both children and adults,” said study author Dr. Jay Desai, a Clinical Neurologist at CHLA.
What’s more, they found a proportional response among volume of blood flow. “Blood flow was inversely correlated to the degree of stuttering – the more severe the stuttering, the less blood flow to this part of the brain,” noted Desai.
Why Blood Flow Impacts Stuttering
Previous research has shown the importance of Broca’s area to one’s speech and fluency. A recent study from Johns Hopkins Medicine found that Broca’s area, which is located in the frontal cortex, essentially develops the plan for what a person might say and is instrumental in directing the flow of speech.
The Johns Hopkins study refers to Broca’s area as the brain’s “scriptwriter,” so it makes sense that stuttering, which is characterized by broken, interrupted speech, would be affected by variations in this part of the brain.
“That stuttering is related to speech and language-based brain circuits seems clear,” said Dr. Bradley S. Peterson, director of the Institute for the Developing Mind at CHLA.
The researchers also found that low cerebral blood flow among other parts of the brain that control emotions can contribute to worsened stuttering.
“Attention-regulating portions of the brain are related to control circuits that are important in governing behavior. People with changes here are more likely to stutter and have more severe stuttering,” said Peterson. “And emotions like anxiety and stress also tend to make stuttering worse, likely because this network interacts with language and attention control circuits,” he added.
Stuttering typically begins during childhood, and about 5% of the general population will experience stuttering at some point their lives, according to the American Speech-Language-Hearing Association. Fewer than 1% of people experience stuttering over the duration of their lives, and while most people overcome stuttering by the time they reach adulthood, about 25% see it persist.
The new study offers new insight into the condition, giving scientists a “different window into the brain” that may provide additional clues for treatment, note the researchers.