Abstract
The visual system can determine motion and depth from ambiguous information contained in images projected onto both retinas over space and time. The key to the way the system overcomes such ambiguity lies in dependency among multiple cues—such as spatial displacement over time, binocular spatial disparity (SD), and interocular time delay(TD)—which might be established based on prior knowledge or experience. We investigated whether a single ambiguous cue (specifically, interocular time delay) permits depth discrimination and motion perception. The space-time-oriented response profiles in a binocular domain of V1 neurons predict that the depth of an object will be discriminated from TD in a manner similar to that from SD. The correspondence between monocular and binocular profiles predicts that TD will evoke the perception of motion direction, and also the velocity of an object. We conducted a psychophysical investigation of whether TD alone evokes a perception of depth and motion that is consistent with the characteristics of the response profiles reported physiologically. To investigate the perception of depth and motion evoked from TD, we designed a series of psychophysical experiments in which subjects observed moving random dots through a single narrow slit presented on a dichoptic, stereo display system. A one-pixel wide slit was used so that neither the pictorial cue for motion direction or Da Vinci stereopsis was possible. The subjects discriminated the depths evoked from TD in a manner similar to that from SD. Further, the apparent depth and motion direction were independent of occlusion direction, but dependent on TD. Finally, a positive, linear correlation between the depths from TD and SD was observed. These results are consistent with the predictions derived from the response profiles of V1 neurons, which show interdependency in their responses to each cue, indicating that spatial and temporal information is jointly encoded in early vision.
Supported by grant-in-aid for scientific research (KAKENHI 13680861, 15500203) from JSPS.