title: fMRI Analysis-by-Synthesis Reveals a Dorsal Hierarchy That Extracts Surface Slant.
abstract: The brain's skill in estimating the 3-D orientation of viewed surfaces supports a range of behaviors, from placing an object on a nearby table, to planning the best route when hill walking. This ability relies on integrating depth signals across extensive regions of space that exceed the receptive fields of early sensory neurons. Although hierarchical selection and pooling is central to understanding of the ventral visual pathway, the successive operations in the dorsal stream are poorly understood. Here we use computational modeling of human fMRI signals to probe the computations that extract 3-D surface orientation from binocular disparity. To understand how representations evolve across the hierarchy, we developed an inference approach using a series of generative models to explain the empirical fMRI data in different cortical areas. Specifically, we simulated the responses of candidate visual processing algorithms and tested how well they explained fMRI responses. Thereby we demonstrate a hierarchical refinement of visual representations moving from the representation of edges and figure-ground segmentation (V1, V2) to spatially extensive disparity gradients in V3A. We show that responses in V3A are little affected by low-level image covariates, and have a partial tolerance to the overall depth position. Finally, we show that responses in V3A parallel perceptual judgments of slant. This reveals a relatively short computational hierarchy that captures key information about the 3-D structure of nearby surfaces, and more generally demonstrates an analysis approach that may be of merit in a diverse range of brain imaging domains.
authors.affiliation: Center for Information and Neural Networks, National Institute of Information and Communications Technology, Osaka, 565-0871, Japan, Graduate School of Frontier Biosciences, Osaka University, Osaka, 565-0871, Japan, Japan Society for the Promotion of Sciences, Tokyo, 102-0083, Japan, School of Psychology, University of Birmingham, Birmingham B15 2TT, United Kingdom, and.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Ban
authors.affiliation: School of Psychology, University of Birmingham, Birmingham B15 2TT, United Kingdom, and Department of Psychology, University of Cambridge, Cambridge CB2 3EB, United Kingdom aew69@cam.ac.uk.
authors.forename: Andrew E
authors.initials: AE
authors.lastname: Welchman
mesh_terms: D000704:Analysis of Variance; D001921:Brain / Q000098:blood supply* / Q000502:physiology; D003463:Cues; D003867:Depth Perception / Q000502:physiology*; D004192:Discrimination, Psychological; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D009949:Orientation; D010100:Oxygen / Q000097:blood; D010775:Photic Stimulation; D011601:Psychophysics; D012044:Regression Analysis; D015203:Reproducibility of Results; D013334:Students; D014495:Universities; D015357:Vision Disparity; D014795:Visual Pathways
chemical_list: D010100:Oxygen
keywords: 3-D vision; binocular disparity; fMRI; slant