MRI-Based topographic parcellation of human cerebral white matter and nuclei II. Rationale and applications with systematics of cerebral connectivity

We describe a system for parcellation of the human cerebral white matter an d nuclei, based upon magnetic resonance images. An algorithm for subdivisio n of the cerebral central white matter according to topographic criteria is developed in the companion manuscript. In the present paper we provide a r ationale for this system of parcellation of the central white matter and we extend the system of cerebral parcellation to include principal subcortica l gray structures such as the thalamus and the basal ganglia. The volumetri c measures of the subcortical gray and white matter parcellation units in 2 0 young adult brains are computed and reported here as well. In addition, w ith the comprehensive system for cerebral gray and white matter structure p arcellation as reference, we formulate a systematics of forebrain connectiv ity. The degree to which functionally specific brain areas correspond to to pographically specific areas is an open empirical issue. The resolution of this issue requires the development of topographically specific anatomic an alyses, such as presented in the current system, and the application of suc h systems to a comprehensive set of functional-anatomic correlation studies in order to establish the degree of structural-functional correspondence. This system is expected to be applied in both cognitive and clinical neuros cience as an MRI-based topographic systematics of human forebrain anatomy w ith normative volumetric reference and also as a system of reference for th e anatomic organization of specific neural systems as disrupted by focal le sions in lesion-deficit correlations. (C) 1999 Academic Press.