%0 Journal Article
%T Functional Topography of Human Corpus Callosum: An fMRI Mapping Study
%A Mara Fabri
%A Gabriele Polonara
%J Neural Plasticity
%D 2013
%I Hindawi Publishing Corporation
%R 10.1155/2013/251308
%X The concept of a topographical map of the corpus callosum (CC) has emerged from human lesion studies and from electrophysiological and anatomical tracing investigations in other mammals. Over the last few years a rising number of researchers have been reporting functional magnetic resonance imaging (fMRI) activation in white matter, particularly the CC. In this study the scope for describing CC topography with fMRI was explored by evoking activation through simple sensory stimulation and motor tasks. We reviewed our published and unpublished fMRI and diffusion tensor imaging data on the cortical representation of tactile, gustatory, auditory, and visual sensitivity and of motor activation, obtained in 36 normal volunteers and in 6 patients with partial callosotomy. Activation foci were consistently detected in discrete CC regions: anterior (taste stimuli), central (motor tasks), central and posterior (tactile stimuli), and splenium (auditory and visual stimuli). Reconstruction of callosal fibers connecting activated primary gustatory, motor, somatosensory, auditory, and visual cortices by diffusion tensor tracking showed bundles crossing, respectively, through the genu, anterior and posterior body, and splenium, at sites harboring fMRI foci. These data confirm that the CC commissure has a topographical organization and demonstrate that its functional topography can be explored with fMRI. 1. Introduction The corpus callosum (CC) connects the cerebral hemispheres and provides for interhemispheric integration and transfer of information. Ever since electrophysiological recording from callosal fibers showed somatosensory receptive fields in the anterior portion of the cat commissure [1, 2] and visual inputs to the splenium [3, 4], it was hypothesized that the CC was endowed with a topographical organization. Subsequent electrophysiological [5] and neuroanatomical findings [6, 7] obtained from nonhuman primates after selective cortical ablation or tracing injections, plus a vast body of data ranging from postmortem investigations [8] to studies of patients with CC lesions or callosal resection (split-brain subjects; [9]; see [10¨C12] for a review), lent further support to the notion. Such organization seems to result in modality-specific regions [13], where the anterior callosal fibers interconnecting the frontal lobes transfer motor information and posterior fibers, which connect the parietal, temporal, and occipital lobes bilaterally, are responsible for the integration of somatosensory (posterior midbody), auditory (isthmus), and visual (splenium)
%U http://www.hindawi.com/journals/np/2013/251308/