Atypical anatomy in children and adults with persistent developmental stuttering
Description
A larger right prefrontal and a larger left occipital lobe (lobar asymmetry) and a larger left planum temporale (PT) are consistent asymmetries found in the human brain. Reduced or reversed asymmetries from these typical configurations are considered atypical and may be markers of atypical function. Atypical lobar and PT asymmetries have been found in adults with persistent developmental stuttering (PDS). These atypical asymmetries may represent a neural risk for developing PDS. To further understand the development of these asymmetries; volumes, ratios and asymmetry quotients were investigated in three groups: (1) healthy right-handed boys and girls ages 8--13 (2) righthanded boys with PDS and matched controls ages 8--13 (3) right-handed adult men with PDS and matched controls ages 21--49. The healthy boys and girls displayed sex-linked differences. Boys had larger total brain and total gray matter volumes than girls. Due to sex-linked gray matter differences, boys had larger right prefrontal and left occipital volumes which lead to a greater magnitude of brain torque. The PT was leftward in both sexes. The boys with PDS differed in multiple anatomical areas compared to controls. The PDS group had more total white matter and a smaller gray-to-white matter ratio in the right hemisphere compared to controls. The PDS group had a smaller right prefrontal region due to decreased prefrontal inferior gray matter. The occipital volume and asymmetry patterns also differed between groups. Controls had the expected leftward asymmetry while the PDS group was more atypical. Thus, the overall brain torque was more symmetrical in the PDS group. The stuttering severity scores positively correlated with right prefrontal white matter volume. The PT was leftward in the boys with no group difference. Right-handed men with PDS and controls did not differ in lobar volumes and asymmetries. The PT was more symmetrical in the PDS group than controls. Interestingly, in all PDS subjects and controls, the prefrontal and occipital white matter asymmetries followed the typical brain torque configuration while the gray matter asymmetries were more variable. This observation indicates that white matter volumes may be responsible for the typical brain torque configuration