Grouping signals in primate visual cortex.

Our understanding of scenes as organized collections of objects is remarkably stable despite eye movements. This may be due, in part, to neurons in area V2 that signal which side of a border is foreground (border ownership [BOS]) for hundreds of milliseconds after the defining information is deleted, and this signal transfers with eye movements. The grouping model explains this through a hypothetical short-latency grouping signal downstream. This would be a persistent pattern of preferred ownership toward the center of the receptive field, which also occurs de novo after eye movements. Our recordings identify such a grouping signal in macaque V4, which occurs fast enough to underlie BOS in V2. These V4 neurons are not as strongly tuned for contrast polarity as are BOS neurons. This suggests a division of labor in which grouping signals provide spatiotemporal continuity of segmented surfaces, whereas BOS neurons link this with feature information.