Identifying cortical areas that underlie the transformation from 2D retinal to 3D head-centric motion signals

• Published in: NeuroImage (Orlando, Fla.) Fla.), 2023-04, Vol.270, p.119909-119909, Article 119909
• Main Authors: Wen, Puti, Landy, Michael S., Rokers, Bas
• Format: Article
• Language: English
• Subjects: Binocular vision; Depth perception; Eye; Functional magnetic resonance imaging; Humans; Information processing; Motion; Motion detection; Motion Perception; Photic Stimulation; Retina; Retina - diagnostic imaging; Sensory mechanisms; Stereoscopic displays; Visual cortex; Visual Cortex - diagnostic imaging; Visual Perception; Visual system
• ISSN: 1053-8119; 1095-9572
• DOI: 10.1016/j.neuroimage.2023.119909

•We investigated the representation of binocular motion across the visual hierarchy.•We could decode motion direction in 3 cortical clusters: V1-V3, hMT+, and V3A/IPS0.•Performance in V1-V3 was best explained based on decoding of retinal motion signals.•Performance in the other clusters was better explained by associated 3D motion.•Results reveal cortical areas and transformations that underly motion perception. Accurate motion perception requires that the visual system integrate the 2D retinal motion signals received by the two eyes into a single representation of 3D motion. However, most experimental paradigms present the same stimulus to the two eyes, signaling motion limited to a 2D fronto-parallel plane. Such paradigms are unable to dissociate the representation of 3D head-centric motion signals (i.e., 3D object motion relative to the observer) from the associated 2D retinal motion signals. Here, we used stereoscopic displays to present separate motion signals to the two eyes and examined their representation in visual cortex using fMRI. Specifically, we presented random-dot motion stimuli that specified various 3D head-centric motion directions. We also presented control stimuli, which matched the motion energy of the retinal signals, but were inconsistent with any 3D motion direction. We decoded motion direction from BOLD activity using a probabilistic decoding algorithm. We found that 3D motion direction signals can be reliably decoded in three major clusters in the human visual system. Critically, in early visual cortex (V1-V3), we found no significant difference in decoding performance between stimuli specifying 3D motion directions and the control stimuli, suggesting that these areas represent the 2D retinal motion signals, rather than 3D head-centric motion itself. In voxels in and surrounding hMT and IPS0 however, decoding performance was consistently superior for stimuli that specified 3D motion directions compared to control stimuli. Our results reveal the parts of the visual processing hierarchy that are critical for the transformation of retinal into 3D head-centric motion signals and suggest a role for IPS0 in their representation, in addition to its sensitivity to 3D object structure and static depth.