Abstract
As we move from place to place, we change both our location and our orientation relative to the world. Neurophysiological studies indicate that location and orientation are represented by different sets of neurons in animals. We used fMRI to identify cortical regions differentially sensitive to changes in location (i.e. translations) or changes in orientation (i.e. rotations) in humans. Subjects viewed 4-second-long “movie clips” depicting the visual input one would see if one were moving forward, moving sideways, or rotating in place within a real-world environment. In control conditions, subjects viewed (1) spatially “scrambled” versions of the same movie clips, (2) a series of static images from these movie clips. Format (movie, scrambled movie, static photos) was crossed with movement type (forward translation, sideways translations, rotation) to give 9 different conditions in a 3×3 design. A conjunction analysis identified “translation” voxels that showed both of the following patterns: (1) greater response to [translations- scrambled translations] than to [rotations-scrambled rotations], and (2) greater response to [translations-static translations] than to [rotations-static rotations]. The reverse contrasts were used to identify “rotation” voxels. Preliminary results indicate that a region in the transverse occipital sulcus responds preferentially to translational motion while an intraparietal sulcus/superior parietal region responds preferentially to rotational motion. We hypothesize that these regions might be involved in calculating distances and angles between the body and fixed scene-defining surfaces in order to track translation and rotation of the body through space.