A region of the brain thought to control speech production develops abnormally in children who stutter - a pattern that persists into adulthood, according to new University of Alberta research.
In the first study to use MRI imaging to examine brain development in both children and adults who stutter, researchers at the U of A’s Institute for Stuttering Treatment and Research (ISTAR) 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.
“In every other region of the brain we studied, we saw a typical pattern of brain matter development. These findings implicate Broca’s area as a crucial region associated with stuttering,” said Deryk Beal, ISTAR executive director and an assistant professor in the Faculty of Rehabilitation Medicine.
Beal’s team, which included collaborators from the University of Toronto, 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.
Brain abnormality persists with age in people who stutter
The research 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, Beal explained, is actually a good thing because it reflects how the brain gets more efficient as we age, requiring fewer neural resources.
Aphasia is the term used to describe an acquired loss of language that causes problems with any or all of the following: speaking, listening, reading and writing. Some people with aphasia have trouble using words and sentences (expressive aphasia). Some have problems understanding others (receptive aphasia). Others with aphasia struggle with both using words and understanding (global aphasia). Aphasia can cause problems with spoken language (talking and understanding) and written language (reading and writing). Typically, reading and writing are more impaired than talking or understanding. The severity of the aphasia depends on the amount and location of the damage to the brain.
Broca’s (expressive or motor) Aphasia
Damage to a discrete part of a the brain in the left frontal lobe (Broca’s area) of the language-dominant hemisphere has been shown to significantly affect use of spontaneous speech and motor speech control. Words may be uttered very slowly and poorly articulated. Speech may be labored and consist primarily of nouns, verbs or important adjectives. Speech takes on a telegraphic character. People suffering from Broca’s aphasia have great difficulty with repetition and a severe impairment in writing. In some patients, however, the understanding of spoken and written language may be relatively well-preserved. The non-fluent variant of primary progressive aphasia (nfvPPA) is a type of expressive aphasia.
If damage encompasses both Wernicke’s and Broca’s areas, global aphasia can occur. In this case, all aspects of speech and language are affected. Patients can say a few words at most and understand only a few words and phrases. They usually cannot carry out commands or name objects. They cannot read or write or repeat words said to them.
“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,” Beal said.
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.
“It’s like the chicken and the egg,” Beal explained. “We don’t know if the changes we are seeing 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.”
Beal’s 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,” he says, like “having a flipbook of how the brain changes over the lifespan instead of just one image at a specific age.”
What is Broca’s area?
It is the motor speech area.
Motor? Yeah, it helps in movements required to produce speech.
What is Wernicke’s area?
It is the sensory speech area.
Sensory? Yes, it helps you understand speech.
It also helps in usage of correct words to express our thoughts.
Where is Broca’s area located?
Broca’s area is located in the frontal lobe.
(Frontal lobe also contains the general motor and premotor areas, so it’s easy to make the association!)
Where is Wernicke’s area located?
Wernicke’s area is located in the parietal and temporal lobe.
(Parietal lobe also contains the general sensory area, gustatory area for taste sensation.. So it’s easy to remember sensory speech area is located in the Parietal lobe!)
What is Broca’s aphasia?
It is expressive aphasia (non-fluent aphasia).
Loss of the ability to produce language (spoken or written).
Patient have insight to their problem and are frustrated.
Beal said 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 kids who stutter and later recover.
“That will help us know how the brains of kids who stutter and recover change to help them cure themselves. We can then start to change our treatments so that they impact all kids in this way.”
The study was published in the journal Frontiers in Human Neuroscience in an early online release, and received funding from the SickKids Foundation, the Canadian Institutes of Health Research and the National Institute on Deafness and Other Communication Disorders.
University of Alberta
Frontiers in Human Neuroscience