Detailed topographic and functional mapping of areas within the posterior lateral-occipital and hMT/V5 complex at 3T using functional grid analysis

Introduction The human hMT/V5 complex was initially identified as a region that exhibits sensitivity to motion [1, 2] and was in analogy to the monkey believed to consist of several motion sensitive areas [3]. Huk [4] demonstrated the existence of two subregions, commonly called hMT/V5 and MST, using ipsilateral stimuli. Kourtzi [5] suggested an additional sub-division of the hMT/V5 complex into two sub-regions based on an observed overlap of motion and shape sensitive regions. This called into question a clear functional distinction between the hMT/V5 complex and the lateral occipital complex (LOC). Later studies yielded field maps for areas LO1 and LO2 within the LOC [6], but maps for areas hMT/V5 have only recently emerged. These suggest two conflicting models for the relationship of hMT/V5 to neighboring areas LO1/2: a discontinuous model with an area of peripheral eccentricity separating hMT/V5 and LO1/2 [7] and a continuous model in which LO1/2, hMT/V5, and MST represent neighboring areas with common eccentricity distribution [8]. In this study, we used functional magnetic resonance imaging (fMRI) to identify and localize areas within the hMT/V5 complex and the LOC and recorded responses to standard localizers to characterize all areas. We further developed a novel approach to group analysis to increase the specificity of the analysis to within a fraction of an individual area.