Children who stutter have less grey matter in key regions of the brain responsible for speech production than children who do not stutter, according to a new study by a University of Alberta researcher.
The findings augment our understanding of how the brain is built for speech production and why people stutter. They also affirm the importance of seeking treatment early, using approaches such as those pioneered by the Institute for Stuttering Treatment and Research in the Faculty of Rehabilitation Medicine at the U of A, said Deryk Beal, the Institute’s executive director.
“You can never be quite sure whether the differences in brain structure or function you’re looking at were the result of a lifetime of coping with a speech disorder or whether those brain differences were there from the beginning,"
explained Beal, a speech-language pathologist.
Grey And White Matter Development
Previous research has used MRI scans to look at structural differences between the brains of adults who stutter and those who do not. The problem with that approach is the scans come years after the onset of stuttering, typically between the ages of two and five years, Beal said.
For his study, Beal scanned the brains of 28 children ranging from five to 12 years old. Half the children were diagnosed with stuttering; the other half served as a control.
Results showed that the inferior frontal gyrus region of the brain develops abnormally in children who stutter. This is important because that part of the brain is thought to control articulatory coding - taking information our brain understands about language and sounds and coding it into speech movements.
“If you think about the characteristics of stuttering – repetitions of the first sounds or syllables in a word, prolongation of sounds in a word – it’s easy to hypothesize that it’s a speech-motor-control problem,” explained Beal. “The type of stuttering treatment we deliver at ISTAR is delivered with this limitation of the speech system in mind, and we have good success in stuttering treatment."
He sees the results as a first step toward testing to see how grey matter volumes are influenced by stuttering treatment and understanding motor-sequence learning differences between children who stutter and those who do not.
Deryk S. Beal, Vincent L. Gracco, Jane Brettschneider, Robert M. Kroll, Luc F. De Nil A voxel-based morphometry (VBM) analysis of regional grey and white matter volume abnormalities within the speech production network of children who stutter Cortex, 2013; 49 (8): 2151 DOI: 10.1016/j.cortex.2012.08.013
Image: Broca’s area, the region of the brain responsible for speech production, develops abnormally in people who stutter. Credit: Deryk Beal/University of Alberta