title: All Pulfrich-like illusions can be explained without joint encoding of motion and disparity.
abstract: In the Pulfrich effect, an interocular time delay results in the perception of depth. Two modified versions, the stroboscopic Pulfrich effect and dynamic visual noise with a delay, are generally explained by postulating an early stage of space/time-inseparable filtering, encoding motion and disparity jointly. However, most disparity sensors in monkey V1 do not show joint motion/disparity encoding, and we recently showed that depth perception in the stroboscopic Pulfrich effect is equally compatible with space/time-separable filtering. Here, we demonstrate that this filtering can be implemented with a population of physiologically plausible energy model units. Similar results are obtained whether the neurons are pure disparity sensors (like most V1 neurons) or joint motion/disparity sensors (like MT). We also demonstrate that the dynamic noise stimulus produces correlations between the activity in pure disparity sensors, and in a separate population of pure motion sensors. These correlations are sufficient to explain the percept. Thus, joint encoding of motion and disparity is not required to explain depth perception in Pulfrich-like stimuli: a brain which encoded motion and disparity in entirely separate neuronal pathways could still experience all of these illusions.
authors.affiliation: Laboratory of Sensorimotor Research, National Eye Institute, National Institutes of Health, Bethesda, MD, USA. J.C.A.Read@ncl.ac.uk
authors.forename: Jenny C A
authors.initials: JC
authors.lastname: Read
authors.forename: Bruce G
authors.initials: BG
authors.lastname: Cumming
mesh_terms: D000818:Animals; D003198:Computer Simulation; D003867:Depth Perception / Q000502:physiology*; D006801:Humans; D007088:Illusions / Q000502:physiology*; D008954:Models, Biological; D009039:Motion Perception / Q000502:physiology*; D009475:Neurons, Afferent / Q000502:physiology*; D010775:Photic Stimulation / Q000379:methods; D013997:Time Factors; D015357:Vision Disparity / Q000502:physiology*