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The Journal of Neuroscience, October 29, 2008, 28(44):11315-11327; doi:10.1523/JNEUROSCI.2728-08.2008

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Behavioral/Systems/Cognitive
Multivoxel Pattern Selectivity for Perceptually Relevant Binocular Disparities in the Human Brain

Tim J. Preston, Sheng Li, Zoe Kourtzi, and Andrew E. Welchman

School of Psychology, University of Birmingham, Edgbaston, Birmingham B15 2TT, United Kingdom

Correspondence should be addressed to Andrew E. Welchman, School of Psychology, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK. Email: a.e.welchman{at}bham.ac.uk

Processing of binocular disparity is thought to be widespread throughout cortex, highlighting its importance for perception and action. Yet the computations and functional roles underlying this activity across areas remain largely unknown. Here, we trace the neural representations mediating depth perception across human brain areas using multivariate analysis methods and high-resolution imaging. Presenting disparity-defined planes, we determine functional magnetic resonance imaging (fMRI) selectivity to near versus far depth positions. First, we test the perceptual relevance of this selectivity, comparing the pattern-based decoding of fMRI responses evoked by random dot stereograms that support depth perception (correlated RDS) with the decoding of stimuli containing disparities to which the perceptual system is blind (anticorrelated RDS). Preferential disparity selectivity for correlated stimuli in dorsal (visual and parietal) areas and higher ventral area LO (lateral occipital area) suggests encoding of perceptually relevant information, in contrast to early (V1, V2) and intermediate ventral (V3v, V4) visual cortical areas that show similar selectivity for both correlated and anticorrelated stimuli. Second, manipulating disparity parametrically, we show that dorsal areas encode the metric disparity structure of the viewed stimuli (i.e., disparity magnitude), whereas ventral area LO appears to represent depth position in a categorical manner (i.e., disparity sign). Our findings suggest that activity in both visual streams is commensurate with the use of disparity for depth perception but the neural computations may differ. Intriguingly, perceptually relevant responses in the dorsal stream are tuned to disparity content and emerge at a comparatively earlier stage than categorical representations for depth position in the ventral stream.

Key words: binocular disparity; stereopsis; multivariate fMRI; depth perception; fMRI; vision

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Received June 15, 2008; revised Aug. 18, 2008; accepted Sept. 18, 2008.

Correspondence should be addressed to Andrew E. Welchman, School of Psychology, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK. Email: a.e.welchman{at}bham.ac.uk

This article has been cited by other articles:

				T. J. Preston, Z. Kourtzi, and A. E. Welchman Adaptive Estimation of Three-Dimensional Structure in the Human Brain J. Neurosci., February 11, 2009; 29(6): 1688 - 1698. [Abstract] [Full Text] [PDF]

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