Event-related Changes in the Spontaneous Brain Activity during 3D Perception from Random-dot Motion

Abstract

Perception of three-dimensional structure from visual motion requires the visual motion to be integrated spatially as well as to be recognized as a 3-D object. Psychophysical studies have been made to investigate how the visual system extracts the three-dimensional structure of objects from the two-dimensional motion of random dots (3-D structure-from-motion: 3D-SFM), though the neural dynamics underlying the reconstruction of a 3-D structure from optic flow is not fully understood. We used neuromagnetic measurements to detect the dynamic brain responses to 3-D structure perception from visual motion in human. Three different visual stimuli were used; (A) 3-D structure-from-motion (SFM): dots moved as if they belonged to a spherical surface rotating horizontally, (B) In-plane rotation (IPR): dots moved as if they belonged to a circle rotating in-plane, or (C) Random motion (RM): dots moved with random direction and random displacement. The results of event-related time-frequency analysis showed significant suppression of alpha band (7–13 Hz) activity in the right occipito-temporal region, and the suppression of beta band (15–25 Hz) activity in the bilateral superior occipital region in the’ sFM’ condition compared to the ‘IPR’ condition. Spatio-temporal imaging of the brain activity using adaptive beamformer method showed that these areas were also involved in the generation of the event-related MEG components observed during the perception of 3-D objects between the latencies of 140 and 220 ms after the onset of random-dot motion. These results suggest that the perception of moving 3-D object from 2-D random-dot motion is accomplished by the activation both in the ventral and dorsal visual pathways.