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.

Variability in perisylvian brain anatomy in healthy adults.

Gray matter volumes of Heschl's gyrus (HG), planum temporale (PT), pars triangularis (PTR), and pars opercularis were measured on MRI in 48 healthy right-handers. There was the expected leftward PT asymmetry in 70.8%, and leftward PTR asymmetry in 64.6% of the sample. When asymmetry patterns within individuals were examined, there was not one typical pattern, rather several typical configurations were found. In addition, some combinations of asymmetry did not exist in our sample suggesting that some perisylvian anatomical configurations may provide a more suitable neural substrate for the development of language than others. There were also sex differences in HG. Men had rightward asymmetry and women demonstrated leftward asymmetry, due to women having smaller right HG, compared to men.

Sex-linked differences in the anatomy of the perisylvian language cortex: a volumetric MRI study of gray matter volumes.

Perisylvian regions important for auditory processing include Heschl's gyrus (HG), the planum temporale (PT), the posterior superior temporal gyrus (pSTG), and the posterior ascending ramus (PAR). Sex-linked differences in language functions and anatomy have been suggested. To examine sex-linked differences, the authors used MRI to measure HG, PT, pSTG, and PAR volumes. Sex differences were found in right HG and right pSTG volumes but not in the left volumes of these structures. For the PT, there were sex differences in asymmetry; women exhibited leftward asymmetry of the PT, whereas men did not exhibit PT asymmetry. These findings suggest that there are sex-linked differences in the anatomy of primary and association auditory cortices.