Is there a difference in brain structure in stutterers and non-stutterers?
Persistent developmental stuttering (PDS) is a speech difficulty that tends to strike in childhood, and is characterized by involuntary stutters during speech production. Although scientists are unsure about the cause of PDS, it has been shown that there is most likely a hereditary component that could results in vulnerability to this disorder. Due to this fact, scientists have predicted that there may be a genetic, anatomical issue within the brain that would lead to PDS. Based on this information, researchers in Germany were interested in whether biological differences in brain structure were apparent in these individuals.
About the study
Ten adult participants who developed PDS by age 8 and ten adults without PDS underwent MRI (Magnetic Resonance Imaging) scans, which are used to observe brain structure. Images of different areas of the brain in each participant were examined, with an emphasis on differences between the two groups.
So, are they different?
Yes! Researchers found that the brain images of participants with PDS showed a significant increase in white matter volume compared to the control group. White matter in the brain is responsible for relaying information between the brain and other areas of the body. The regions of the brain with a significant difference in white matter volume are areas that were known to researchers as areas that are responsible for speech production and language perception, and thus it made sense that those areas would be affected.
Does this mean we can tell if a child will develop PDS based on their brain structure?
Not necessarily. The sample size in this study was fairly small (20 participants total), and should not be used as the sole piece of evidence to make this claim. Although the results of this study indicate that there is a connection between brain volume and this speech deficiency, it is unknown whether an enlargement in white matter is the cause of PDS or if the opposite is true, and that PDS is the cause of white matter enlargement. It is clear that further investigation is required before any assumptions can be made.
Michelle Dolnaya, lead researcher at Simone Friedman Speech-Language Services
Jancke, L., Hanggi, J., Steinmetz, H. (2004). Morphological brain differences between adult stutterers and non-stutterers.BioMed Central Neurology.4, 23.