Anatomical Asymmetries of Anterior Perisylvian Speech-Language Regions

Anterior cortical perisylvian areas important for speech and language functions include the pars triangularis (PTR), comprised of heteromodal association cortex, and the pars opercularis (POP), comprised of motor association cortex. The anatomy of these frontal language regions has not been well studied in large samples, however in smaller samples, leftward asymmetry of these regions has been found. Sex-linked differences have also been suggested, with bilateral activation of frontal language areas in women and leftward activation in men. We used volumetric MRI methods to measure the gray matter volume of the PTR, POP, and diagonal sulcus (DS) in 60 healthy right-handed adults and examined the distribution of asymmetry of these regions. Sex-linked differences in volume and asymmetry of anterior speech regions were also examined. For the PTR, there was a slight leftward asymmetry, however for the POP+DS, there was a slight rightward asymmetry. The DS was present slightly more often in the right hemisphere than in the left hemisphere and its frequency was similar in men and women. There were no significant sex-linked differences in volume or asymmetry for any of these frontal areas. More studies are necessary, looking at the anatomy of anterior language regions in large samples and examining the relationship between anatomy and function.