title: A Distinct Mechanism of Temporal Integration for Motion through Depth.
abstract: Temporal integration of visual motion has been studied extensively within the frontoparallel plane (i.e., 2D). However, the majority of motion occurs within a 3D environment, and it is unknown whether the principles from 2D motion processing generalize to more realistic 3D motion. We therefore characterized and compared temporal integration underlying 2D (left/right) and 3D (toward/away) direction discrimination in human observers, varying motion coherence across a range of viewing durations. The resulting discrimination-versus-duration functions followed three stages, as follows: (1) a steep improvement during the first ∼150 ms, likely reflecting early sensory processing; (2) a subsequent, more gradual benefit of increasing duration over several hundreds of milliseconds, consistent with some form of temporal integration underlying decision formation; and (3) a final stage in which performance ceased to improve with duration over ∼1 s, which is consistent with an upper limit on integration. As previously found, improvements in 2D direction discrimination with time were consistent with near-perfect integration. In contrast, 3D motion sensitivity was lower overall and exhibited a substantial departure from perfect integration. These results confirm that there are overall differences in sensitivity for 2D and 3D motion that are consistent with a sensory difference between binocular and dichoptic sensory mechanisms. They also reveal a difference at the integration stage, in which 3D motion is not accumulated as perfectly as in the 2D motion model system.
authors.affiliation: Institute for Neuroscience, Center for Perceptual Systems, and Departments of Neuroscience and Psychology, The University of Texas at Austin, Austin, Texas 78712 leor.katz@utexas.edu.
authors.forename: Leor N
authors.identifier: http://orcid.org/0000-0002-2742-6533
authors.initials: LN
authors.lastname: Katz
authors.affiliation: Center for Perceptual Systems, and Departments of Neuroscience and Psychology, The University of Texas at Austin, Austin, Texas 78712.
authors.forename: Jay A
authors.initials: JA
authors.lastname: Hennig
authors.affiliation: Institute for Neuroscience, Center for Perceptual Systems, and Psychology, The University of Texas at Austin, Austin, Texas 78712.
authors.forename: Lawrence K
authors.initials: LK
authors.lastname: Cormack
authors.affiliation: Institute for Neuroscience, Center for Perceptual Systems, and Departments of Neuroscience and Psychology, The University of Texas at Austin, Austin, Texas 78712.
authors.forename: Alexander C
authors.identifier: http://orcid.org/0000-0003-1430-6935
authors.initials: AC
authors.lastname: Huk
mesh_terms: D000328:Adult; D003867:Depth Perception / Q000502:physiology*; D004192:Discrimination, Psychological; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009038:Motion; D009039:Motion Perception / Q000502:physiology*; D010775:Photic Stimulation; D011594:Psychometrics; D055815:Young Adult
keywords: 3D motion; decision making; evidence accumulation; stereomotion