Hindawi Publishing Corporation Neural Plasticity Volume 2013, Article ID 251308, 15 pages http://dx.doi.org/10.1155/2013/251308 Research Article Functional Topography of Human Corpus Callosum: An fMRI Mapping Study Mara Fabri 1 and Gabriele Polonara 2 1 Sezione di Neuroscienze e Biologia Cellulare, Dipartimento di Medicina Sperimentale e Clinica, Universit` a Politecnica delle Marche, 60020 Ancona, Italy 2 Sezione di Scienze Radiologiche, Dipartimento di Scienze Cliniche Specialistiche e Odontostomatologiche, Universit` a Politecnica delle Marche, 60020 Ancona, Italy Correspondence should be addressed to Mara Fabri; m.fabri@univpm.it Received 7 September 2012; Revised 26 November 2012; Accepted 4 December 2012 Academic Editor: Giorgio M. Innocenti Copyright © 2013 M. Fabri and G. Polonara. Tis is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Te concept of a topographical map of the corpus callosum (CC) has emerged from human lesion studies and from electro- physiological 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 We reviewed our published and unpublished fMRI and difusion tensor imaging data on the cortical representation of tactile, gustatory, auditory, and visual sensitivity and of motor activation, obtained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 fbers connecting activated primary gustatory, motor, somatosensory, auditory, and visual cortices by difusion tensor tracking showed bundles crossing, respectively, through the genu, anterior and posterior body, and splenium, at sites harboring fMRI foci. Tese data confrm that the CC commissure has a topographical organization and demonstrate that its functional topography can be explored with fMRI. 1. Introduction Te corpus callosum (CC) connects the cerebral hemispheres and provides for interhemispheric integration and transfer of information. Ever since electrophysiological recording from callosal fbers showed somatosensory receptive felds 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 fndings [6, 7] obtained from nonhuman primates afer 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 [10–12] for a review), lent further support to the notion. Such organization seems to result in modality- specifc regions [13], where the anterior callosal fbers inter- connecting the frontal lobes transfer motor information and posterior fbers, which connect the parietal, temporal, and occipital lobes bilaterally, are responsible for the integration of somatosensory (posterior midbody), auditory (isthmus), and visual (splenium) information. Te hypothesis was fnally confrmed by studies largely carried out in subjects with callosal resection. Functional magnetic resonance imaging (fMRI) investigations of split- brain patients by our group [12, 14, 15] provided evidence that interhemispheric transfer in the tactile modality is likely mediated by fbers running through the posterior part of the callosal body, thus confrming that the posterior midbody is the tactual channel. A recent study of nonepileptic patients