MRI studies of the brain: Application of three-dimensional surface-rendering techniques to quantitative morphometry of the supratemporal cortex

New techniques for MRI surface-rendering morphometry were developed to yield more reliable and valid measurements of supratemporal cortical structures. Asymmetry of the planum temporale (PT), a supratemporal region of language-related association cortex, was then investigated in 10 schizophrenics and 10 age-matched controls, and in a larger sample of 12 normal females and 12 age-matched normal males. All subjects were strongly right-handed (Edinburgh Inventory $>$ +.70). Surface area was also assessed for Heschl's gyrus (HG), a supratemporal region of primary auditory cortex. While numerous postmortem studies have documented pronounced asymmetry of the PT, no similar lateralization has been described for HG. Results indicate an interaction between gender and hemisphere for area of the PT, with males having a significantly larger left versus right PT. Left-right differences in PT area were not significant among females. No main effect of gender was found for total (left + right) PT area. No main effects of gender or hemisphere and no interactions were detected for the area of HG. No effect of diagnosis was found for PT or HG, as male schizophrenics showed a normal supratemporal configuration, with a significant left $>$ right asymmetry for PT and no significant lateralization of HG. This result does not confirm reports of reduced PT laterality in schizophrenia. The finding of sexual dimorphism in PT area, however, is consistent with neuropsychological evidence for gender differences in the lateralization of language functions attributable to the supratemporal cortex.