Human cerebral cortex: localization, parcellation, and morphometry with magnetic resonance imaging

We describe a system of parcellation of the human brain that is based on the functional anatomy of the cerebral cortex and that is applied to the analysis of magnetic resonance images. This system is designed to support investigations of hemispheric asymmetries and quantitative lesion localization studies in cognitive neuroscience. The system of cortical subdivision is a neural systems oriented model that approximates subdivisions supported by previous architectonic and functional analyses. It is based primarily on boundaries determined by "limiting fissures." It is completed by a set of coronal planes, keyed to visible anatomic landmarks, which "close" the borders of the parcellation subdivisions. The method depends on computational reconstruction of the primary image data in multiple planes so as to allow the observed pattern of limiting fissures in a given brain to be digitized. In this presentation, the method is applied in order to define the surface anatomy of the cerebral hemispheres in a normal subject. Volumetric measurements of individual cortical regions are compared as hemispheric percentiles to areal perceniiles derived from the analysis of Jouandet et al. (1989), a conceptually related though methodologically different approach. We specifically address the approach to the study of interhemispheric differences and interindividual variations in cortical anatomy.