Occlusion and the interpretation of visual motion: Perceptual, oculomotor, and neuronal effects of context

Light reflected from a typical visual scene creates a richly featured image on the retinal surface. The perceptual interpretation of each feature in this image is an inference about the visual scene that gave rise to it. In making these inferences, the visual system draws upon the larger context within which the feature appears. Although much is now known about the neuronal representation of retinal image features, there have been few attempts to identify neurons that represent the inferred attributes of the visual scene. The experiments in this dissertation address this issue by focusing on the attribute of visual motion. Simple contextual manipulations were devised to alter the perceived depth ordering between surfaces in a scene containing a moving elements. The perceived direction of motion for our stimuli co-varied with;changes in the perceived depth ordering between putative surfaces. When stimulated with these displays, neurons in the primate middle temporal visual area (MT) appeared to represent the perceived rather than the physical motion of the stimulus. Thus, these neurons utilize contextual information to achieve a representation of the visual scene consistent with perceptual experience. Additionally, a strong correlation between the direction of tracking eye movements and reports of perceived motion was observed. This result suggests that tracking eye movements are similarly guided by a neural mechanism dedicated to the recovery of surface velocity.