Contribution of body shape and motion cues to biological motion selectivity in hMT+ and EBA depends on cue reliability

摘要

The perception of biological motion involves the integration of motion cues with form cues such as body shape. Recently it was shown that voxel-wise selectivity for biological motion within motion area hMT+ and extrastriate body area (EBA) correlated with selectivity for static bodies but not with motion (Peelen, Wiggett, & Downing, 2006). This suggested that the response to biological motion in these regions was driven entirely by the response to body selectivity and not by motion. Here we examined if the contribution of motion and body shape selectivity to biological motion selectivity in hMT+, EBA, as well as the fusiform body area (FBA) is fixed or if it relies in part on the reliability of form and motion cues. We hypothesized that while form cues might be most reliable with foveal presentation of stimuli, reliability should decrease if stimuli are presented in more peripheral locations. In contrast, we hypothesized that eccentricity would have little effect on motion cue reliability, leading to an increased contribution of motion selectivity to biological motion selectivity at more peripheral locations. Using fMRI, we identified hMT+, EBA, and FBA using standard localizers. Participants then performed a one-back task on point-light biological motion or tool motion stimuli presented centrally or more than 5o right of left of fixation. Using correlation-based multivoxel pattern analysis (MVPA), we replicated the finding that biological motion selectivity was associated with body selectivity but not motion selectivity in hMT+, EBA, and FBA - but only with foveal presentation. Presenting stimuli at more peripheral locations led to a significant correlation between motion selectivity and biological motion selectivity in hMT+ and EBA. These findings suggest that cue reliability is taken into account as form and motion cues are integrated during the neural processing of biological motion.