Scientists have found that stuttering is linked to changes in brain circuits that control speech production, regulate attention and emotions.
Researchers at Children's Hospital Los Angeles (CHLA) in the US have conducted the first study of its kind using proton magnetic resonance spectroscopy (MRS) to look at brain regions in both adults and children who stutter.
Developmental stuttering is a neuropsychiatric condition; its origins in the brain are only partly known.
In order to measure an index of neural density related to stuttering in circuits and brain regions suspected to be affected, the scientists performed proton shift imaging of the brain in 47 children and 47 adults.
The study included subjects both with and without stuttering.
The researchers found that affected brain regions included major nodes of the Bohland speech-production network associated with the regulation of motor activity; the default-mode network, involved in the regulation of attention; and the emotional-memory network responsible for regulating emotion.
"That stuttering is related to speech and language-based brain circuits seems clear," said Bradley S Peterson from CHLA.
"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.
"Emotions like anxiety and stress also tend to make stuttering worse, likely because this network interacts with language and attention control circuits," he said.
This initial, unique MRS study of stuttering confirmed that disturbances in neuronal or membrane metabolism contribute to the development of stuttering.
Looking at a combination of children and adults in order to detect the effects of stuttering, independent of life-stage, revealed differences between children and adults within both the stuttering and control samples.
This suggests different metabolic profiles in children versus adults who stutter. Few sex-specific effects of stuttering on brain metabolites were observed.
The study was published in the Journal of the American Medical Association (JAMA).