Pattern analysis of biological motion selectivity

One of the most important roles of vision is to provide information about the actions, intentions and identities of other individuals and so to enable successful interactions in a social environment. Critical regions in the human brain for perceiving others have been shown to include (but are not limited to) the posterior fusiform gyrus (Kanwisher et al., 1997; Peelen & Downing, 2005) and the posterior inferior temporal sulcus (Downing et al., 2001). This fMRI study examines the response in these cortical regions to biological motion using point-light walkers. We show that functionally defined body- and face-selective areas in posterior fusiform gyrus, and body- and motion-selective areas in inferior temporal sulcus all respond significantly to “point-light” human motion. We then apply voxel-by-voxel analyses of the response patterns to different stimuli in order to disentangle body-selective from face- and motion-selective responses in our regions of interest. Our analysis shows that, on a voxel-by-voxel basis, only body selectivity is correlated with biological motion selectivity. Biological motion selectivity is not related to motion or face selectivity. We conclude that: i) biological motion, through the process of structure-from-motion, engages areas involved in the analysis of the static human form; ii) body-selective regions in posterior fusiform gyrus and in posterior inferior temporal sulcus overlap with, but are distinct from, face- and motion-selective regions; iii) the interpretation of region-of-interest findings may be substantially altered when multiple patterns of selectivity are considered in parallel.