Sexual dimorphism in anterior speech region: An MRI study of cortical asymmetry and callosal size

We measured the cortical surface of Broca' s area and Planum temporale on b rain MRI sections in 20 volunteers, together with the size of the corpus ca llosum suspected to be sexually dimorphic. We did find sex differences in a symmetry of Broca's area, but in the opposite direction than expected, and a negative correlation between Broca's area asymmetry and anterior corpus c allosum size in women. Results suggest that Broca's area may be a specific target of factors determining sex differences and that an inhibitory rule o f the corpus callosum could account for complex anatomical-functional relat ionships. (C) 1999 Academic Press.