Perceptual segmentation and neural grouping in tilt illusion

Abstract We investigate which neural grouping is relevant to the perception of the global orientations of bars. We examine psychophysically whether perceptual segmentation affects the apparent tilt in X-shaped junctions constructed by solid or illusory bars. The results show that perceptual segmentation is not relevant to the global orientation, except for illusory stimuli. Early level processing, probably in the primary visual cortex (V1), seems to be involved in the determination of global orientation. We propose a network model consisting of V1 neurons and a grouping mechanism which synchronizes the cellular activities based on colinear coupling. The computed bar orientations agree quantitatively with the apparent tilt measured in comparable psychophysical experiments reported elsewhere.