Abstract
Our representation of biological motion allows us to decode its form and direction from impoverished stimulus such as point-light-walkers (PLWs). The dynamic nature of PLWs allows a variety of information to be gleamed from the stimuli, for example, gender, action, emotionality, of the PLW. So far though the majority of experiments have looked at PLWs without binocular disparity information. In the two experiments we assessed the ability to judge directional information of PLWs within a 3D display. In the first experiment participants made a delayed match-to-sample choice on the heading direction of a PLW, with two probe PLWs to choose from. For experiment two we conducted the same task but used repetitive 1Hz transcranial magnetic stimulation (TMS) to probe brain regions implicated within the task. 24 participants took part in experiment 1 where a QUEST procedure was used to measure the perception of angle in conjunction with 3D shutter-glasses to produce disparity information. 8 participants took part in experiment 2 and we tested two cortical sites in two separate conditions: left-hMT+, and left pSTS using the same task. PLW angle judgment was measured three times during each session: baseline before rTMS, post-rTMS and 30 minutes delayed-rTMS. Experiment one revealed an inversion effect for angle sensitivity, with an increased sensitivity for upright PLWs relative to inverted PLWs with a overall difference of 3°. This sensitivity difference disappeared after 1Hz TMS over left-pSTS, with a sensitivity decrease after TMS in both sites irrelevant of orientation. These data provide evidence of a neuronal system tuned towards the angle directions of biological agents. Data suggest that our visual system is optimized for perception of biological motion and shows increased sensitivity f PLW only when presented upright. This ability is selectively impaired after TMS over pSTS, an area implicated in the perception of biological motion.
Meeting abstract presented at VSS 2014