FMRI responses in dorsal visual cortex relate to binocular depth perception for both signal-in-noise and feature difference tasks

Abstract

Event Abstract Back to Event fMRI responses in dorsal visual cortex relate to binocular depth perception for both signal-in-noise and feature difference tasks Matthew L. Patten1, 2 and Andrew E. Welchman2, 3* 1 University of Sydney, School of Psychology, Australia 2 University of Birmingham, School of Psychology, United Kingdom 3 University of Cambridge, Department of Psychology, United Kingdom Background. Binocular disparities are formed by the horizontal separation of the eyes and are used by the visual system to provide a powerful cue to depth and 3D structure. Disparity representations are widespread in the visual cortex, and it is an open challenge to understand the functional relevance of these signals. One framework posits a functional distinction based on disparity magnitude, where coarse and fine disparities are processed in the dorsal and ventral visual pathways respectively. However, evidence that supports this conclusion has typically mixed differences in disparity magnitude with different limiting factors on behavioural performance (internal vs. external noise). To dissociate these factors, we performed two types of disparity tasks that have been used previously but presented stimuli of comparable disparity magnitudes. Method. Participants viewed random-dot stereograms that contained a disparity-defined target plane and judged its depth position (near vs. far). We simultaneously recorded event-related fMRI responses in regions of the visual, temporal and parietal cortices. For the signal-in-noise task, we varied the percentage of dots that defined the position of the target plane in relation to dots with randomly assigned disparities (i.e., an external noise manipulation). For the feature difference task, we titrated the disparity difference between a target plane and its surround (i.e., a task limited by internal noise). Results. We used multi-voxel pattern analysis to decode depth positions from the fMRI activity and constructed ‘fMR-metric’ functions that described decoding performance as a function of signal magnitude. We then generated fMR-metric functions using the parameters from the psychometric results so that we could directly compare behavioural performance and fMRI activity. We found evidence of an association between judged depth and fMRI activity in later dorsal regions: V7, VIPS, POIPS for the signal-in-noise task and VIPS and POIPS for the feature difference task. In contrast, activity in higher ventral cortex was only weakly associated with performance on either task. Discussion. These results indicate that later dorsal regions support perceptually-relevant decisions and reflect a higher stage of disparity processing, quite possibly reading out signals from lower portions of the processing hierarchy to support visual judgments and motor actions. Acknowledgements The research leading to these results received funding from the European Community’s Seventh Framework Programme FP7/2007-2013 (grant agreements PITN-GA-2008-214728 and PIIF-GA-2011-299610) and the Wellcome Trust (095183/Z/10/Z). Keywords: binocular disparity, Depth Perception, external noise, multi-voxel pattern analysis, fMRI, psychophysics. Conference: ACNS-2013 Australasian Cognitive Neuroscience Society Conference, Clayton, Melbourne, Australia, 28 Nov - 1 Dec, 2013. Presentation Type: Poster Topic: Sensation and Perception Citation: Patten ML and Welchman AE (2013). fMRI responses in dorsal visual cortex relate to binocular depth perception for both signal-in-noise and feature difference tasks. Conference Abstract: ACNS-2013 Australasian Cognitive Neuroscience Society Conference. doi: 10.3389/conf.fnhum.2013.212.00061 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 15 Oct 2013; Published Online: 25 Nov 2013. * Correspondence: Dr. Andrew E Welchman, University of Birmingham, School of Psychology, Birmingham, United Kingdom, aew69@cam.ac.uk Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. 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