Graduate School of Frontier Biosciences, Osaka University

Japanese

Effects of generalized pooling on binocular disparity selectivity of neurons in the early visual cortex.

Journal Phil. Trans. R. Soc. B 371: 20150266 (2016)
Authors Daisuke Kato (1), Mika Baba (1, 2), Kota S Sasaki (1, 3), Izumi Ohzawa (1, 3)
  1. Viaual Neuroscience Laboratory, Graduate School of Frontier Biosciences, Osaka University, 1-4 Yamadaoka, Suita, Osaka 565-0871, Japan
  2. National Institute for Physiological Sciences, Okazaki, Aichi 444-8585, Japan
  3. Center for Information and Neural Networks, Osaka University and National Institute of Information and Communications Technology, 1-4 Yamdaoka, Suita, Osaka 565-0871, Japan
Title Effects of generalized pooling on binocular disparity selectivity of neurons in the early visual cortex.
PubMed 27269609
Laboratory Visual Neuroscience Laboratory 〈Prof. Ohzawa〉
Abstract

The key problem of stereoscopic vision is traditionally defined as accurately finding the positional shifts of corresponding object features between left and right images. Here, we demonstrate that the problem must be considered in a four-dimensional parameter space; with respect not only to shifts in space (X, Y), but also spatial frequency (SF) and orientation (OR). The proposed model sums outputs of binocular energy units linearly over the multi-dimensional V1 parameter space (X, Y, SF, OR). Theoretical analyses and physiological experiments show that many binocular neurons achieve sharp binocular tuning properties by pooling the output of multiple neurons with relatively broad tuning. Pooling in the space domain sharpens disparity-selective responses in the SF domain so that the responses to combinations of unmatched left-right SFs are attenuated. Conversely, pooling in the SF domain sharpens disparity selectivity in the space domain, reducing the possibility of false matches. Analogous effects are observed for the OR domain in that the spatial pooling sharpens the binocular tuning in the OR domain. Such neurons become selective to relative orientation disparity. Therefore, pooling allows the visual system to refine binocular information into a form more desirable for stereopsis.

This article is part of the themed issue ‘Vision in our three-dimensional world’.

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Figure 1:
(a) Pooling in the space domain (X, Y) is illustrated schematically. (b) Since V1 cortical sheet is organized according to not only space (X, Y) but also OR and SF, the notion of pooling must be generalized to include these four dimensions. Intuitively, the degree of pooling is determined by the number of subunits (small spheres) included within the pooling sphere (large sphere).