Abstract
When moving around in the world, the human visual system uses both form and motion information to estimate the direction of self-motion (i.e., heading). Here we explored brain areas that integrate motion and form cues for heading perception. We used stimuli consisting of 200 randomly distributed dot pairs oriented toward a locus on a screen (the form-defined focus of expansion (FOE)) but moved away from a different locus (the motion-defined FOE) to simulate observer translation. In Experiment 1, we fixed the motion-defined FOE at the display center and shifted the form-defined FOE from -5° to 5° at the step of 2°. In Experiment 2, the form- and motion-defined FOEs were congruent (i.e., at the same location in the display) or incongruent (i.e., on the opposite side of the display) but had the same shifts. Participants made a task-irrelevant (luminance discrimination) judgment during scanning. We preformed the searchlight and ROI-based multiple voxel pattern analysis and found that early visual areas (V1, V2) decoded both form- and motion-defined FOEs but could not discriminate the congruent and incongruent conditions, suggesting that these areas do not integrate form and motion cues for heading perception. The higher ventral areas (V3v, V4v) decoded form- but not motion-defined FOE while the dorsal areas (MT+) and parietal lobe (VIP , CSV) decoded motion- but not form-defined FOE. In contrast, the higher dorsal areas (V3d, V3a, V7, KO) not only decoded both form- and motion-defined FOEs but also dissociated the congruent and incongruent conditions, suggesting that they contribute to the integration of form and motion cues for heading perception. Our findings provide the first empirical evidence suggesting that form and motion information are first processed along separate pathways and then integrated in the higher dorsal areas for the final estimation of heading during self-motion.
Meeting abstract presented at VSS 2018