Kaylie J. Capurro¹, Arnab Biswas¹, Giselle R. Urquijo¹, Yu Zhao¹, Mark D. Lescroart¹; ¹University of Nevada, Reno

The fundus of the superior temporal sulcus (FST) has been established in macaques to be selective for 3D motion. Here, we investigate the region in and around the recently-proposed human homolog of FST for selectivity to different kinds of 3D motion: self motion and object motion. We localize hMT and FST with established functional contrasts. To investigate tuning for object and self motion, we created rendered animations of geometric objects tumbling in space and animations suggestive of self motion down a hallway. We used the optic flow of these renders to define random-dot kinematogram (RDK) versions of the animations. Subjects viewed these RDKs in 3D anaglyph form while in an MRI scanner. To localize areas selective for object motion, we contrasted the object RDKs with an expanding dot condition and a linear full-field dot motion condition. To localize areas selective for self motion, we contrasted the hallway RDKs with the linear full-field dot motion condition. Contrasts were projected onto flatmaps and ROIs for hMT and FST were delineated for each participant. We find that the object motion contrast activates regions ventral to and overlapping with the posterior portion of FST. We find that the self motion contrast activates regions anterior to and partially overlapping with FST. Our findings suggest that there is a gradual shift in tuning from object motion to scene or self motion, going from posterior to anterior across the proposed location of human FST. Since we typically interact with objects at a closer distance than we do scenes, we propose that the representation of 3D motion in this region may be organized according to the distances at which we encounter different types of motion.

Acknowledgements: Supported by NSF CAREER #2340895 to M.D.L