An fMRI Study of Cortical Responses for Reflectance-specific Image Motion

Abstract

Competent visual behavior depends on the accurate perception of the shape and material of objects in the world. These perceptual decisions can be informed by the neural processing of high-dimensional motion flow patterns that begin at the retina and continue through several cortical areas. While we have a reasonable understanding of the computational, perceptual and neural basis of shape from motion flow, we know relatively little of how the visual system infers material from motion. Recently, we discovered several surface reflectance-specific motion characteristics that the visual system may use to determine whether a rotating object appears shiny or matte (Doerschner et al., Current Biology, 2011). We are now using neuroimaging to look for the neural basis of material-specific motion flows. To this end, we have designed an experiment to test whether neural responses to patterns of object surface motion flow that distinguish shiny from matte surfaces can be localized to particular brain regions. Stimuli were computer-rendered movies of 5 unfamiliar, rotating objects with 'sticky' (diffusely reflecting) and 'slipping' (100% specularly reflecting) conditions (image flow) and their dot flow patterns, the latter calculated by a phase-based optical flow method (Gautama et al., 2002). We set the retinotopic visual areas and the human motion complex (hMT+) as primary regions of interest and measured BOLD signals at 3T (n=6). We found that responses in V1, V2, V3, hV4, and hMT+ were significantly higher for shiny than matte motion (all p <0.05). Such differences were present for both images and dot flows, with the exception of hV4 where it was only observed for images.

Meeting abstract presented at VSS 2013