title: Human visual cortical responses to specular and matte motion flows.
abstract: Determining the compositional properties of surfaces in the environment is an important visual capacity. One such property is specular reflectance, which encompasses the range from matte to shiny surfaces. Visual estimation of specular reflectance can be informed by characteristic motion profiles; a surface with a specular reflectance that is difficult to determine while static can be confidently disambiguated when set in motion. Here, we used fMRI to trace the sensitivity of human visual cortex to such motion cues, both with and without photometric cues to specular reflectance. Participants viewed rotating blob-like objects that were rendered as images (photometric) or dots (kinematic) with either matte-consistent or shiny-consistent specular reflectance profiles. We were unable to identify any areas in low and mid-level human visual cortex that responded preferentially to surface specular reflectance from motion. However, univariate and multivariate analyses identified several visual areas; V1, V2, V3, V3A/B, and hMT+, capable of differentiating shiny from matte surface flows. These results indicate that the machinery for extracting kinematic cues is present in human visual cortex, but the areas involved in integrating such information with the photometric cues necessary for surface specular reflectance remain unclear.
authors.affiliation: Department of Computer Science and Engineering, Korea University Seoul, South Korea.
authors.forename: Tae-Eui
authors.initials: TE
authors.lastname: Kam
authors.affiliation: Department of Brain and Cognitive Engineering, Korea University Seoul, South Korea ; School of Psychology, UNSW Australia Sydney, NSW, Australia ; Department of Psychology, University of Minnesota Minneapolis, MN, USA.
authors.forename: Damien J
authors.initials: DJ
authors.lastname: Mannion
authors.affiliation: Department of Computer Science and Engineering, Korea University Seoul, South Korea ; Department of Brain and Cognitive Engineering, Korea University Seoul, South Korea.
authors.forename: Seong-Whan
authors.initials: SW
authors.lastname: Lee
authors.affiliation: Department of Psychology, Bilkent University Ankara, Turkey ; National Magnetic Resonance Research Center, Bilkent University Ankara, Turkey ; Department of Psychology, Justus-Liebig-University Giessen Giessen, Germany.
authors.forename: Katja
authors.initials: K
authors.lastname: Doerschner
authors.affiliation: Department of Brain and Cognitive Engineering, Korea University Seoul, South Korea ; Department of Psychology, University of Minnesota Minneapolis, MN, USA.
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Kersten
keywords: classification; functional magnetic resonance imaging (fMRI); motion flow; surface materials; visual perception