A region of the brain thought to control speech production develops abnormally in children who stutter, a pattern that persists into adulthood, according to a new study from the University of Alberta and the University of Toronto. In the first study to use MRI imaging to examine brain development in both children and adults who stutter, the researchers found abnormal development of grey matter in Broca’s area, the region of the frontal lobe responsible for speech. It was the only abnormality found in the 30 regions of the brain the research team investigated.
The team state that in every other region of the brain they studied they saw a typical pattern of brain matter development. These findings implicate Broca’s area as a crucial region associated with stuttering. The opensource study is published in the journal Frontiers in Human Neuroscience.
The researchers studied MRI images of the brains of 116 males between the ages of six and 48 years, both the largest group and widest age range for such a study. Roughly half the participants stuttered; the rest served as a control group.
The team observed a steady, and expected, decline in the cortical thickness of grey matter in the control group, a decline not observed in people who stutter. This decline in thickness is actually a good thing because it reflects how the brain gets more efficient as we age, requiring fewer neural resources.
One interpretation of this finding could be that this area, in people who stutter, does not operate as efficiently within the brain network for speech production. Though the results confirm that this region of the brain develops abnormally in people who stutter, scientists still cannot say definitively that Broca’s region is responsible for stuttering.
The team explain that they don’t know if the changes they saw in this region of the brain are the result of a reaction in the brain to stuttered speech or some other difference in how the brain is operating elsewhere, or indeed if these changes are the cause of the disorder.
The team previously discovered that children who stutter have less grey matter volume, a finding that was more like a snapshot in time showing how kids who stutter differ from those without the speech disorder. This newer research is a huge improvement like having a flipbook of how the brain changes over the lifespan instead of just one image at a specific age.
The team summise that the findings support the need for an even larger long-term study of brain development from infancy to adulthood to look at how brain growth in speech areas differs between children who stutter, those who don’t, and children who stutter and later recover.
Source: University of Alberta