August 2023
Volume 23, Issue 9
Open Access
Vision Sciences Society Annual Meeting Abstract  |   August 2023
Evidence for binocular differencing and summing channels for chromatic stimuli
Author Affiliations & Notes
  • Yoel Yakobi
    McGill University
  • Clara Wang
    McGill University
  • Frederick Kingdom
    McGill University
  • Footnotes
    Acknowledgements  Supported by Canadian Institute of Health Research (CIHR) grant #MOP 123349 to FK and research bursaries from the McGill Faculty of Medicine and Health Sciences to YY and CW.
Journal of Vision August 2023, Vol.23, 5127. doi:
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      Yoel Yakobi, Clara Wang, Frederick Kingdom; Evidence for binocular differencing and summing channels for chromatic stimuli. Journal of Vision 2023;23(9):5127.

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      © ARVO (1962-2015); The Authors (2016-present)

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Mounting evidence suggests that in binocular vision there exist channels that sum (S+) and difference (S-) the luminance contrast signals from the two eyes. While there is strong evidence from studies of chromatic binocular summation for chromatic S+ channels, there is little or no direct evidence for chromatic S- channels. Here we test for the presence of chromatic S- channels using a two-interval forced-choice surround masking paradigm aimed at selectively attenuating S+ and S- channel signals. Interocularly correlated (C) gratings are believed to be detected by S+ channels and interocularly anticorrelated (A) gratings by S- channels, so C and A surround masks would be expected to selectively attenuate C and A test stimuli respectively. Stimuli were horizontally oriented 0.5 cpd gratings. The test stimulus was contained in a hard-edged 2 deg diameter circular window separated by a 0.25 deg gap from the 6.5 deg diameter circular mask grating. Stimuli were defined along the three cardinal axes of color space to produce what may be nominally termed red-green (RG), blue-yellow (BY) and luminance (LUM) stimuli. Masks and test stimuli were always of the same color type. Measurements consisted of binocular C and A detection thresholds and monocular detection thresholds, allowing us to determine the degree of binocular summation in the C and A stimuli. Results showed that all three color types exhibited the selective masking associated with the detection of stimuli in the presence of S+ and S- channels. For all three color types, the differential effect of the two types of masks was greater for the A compared to C stimuli. Binocular summation for both the A and C stimuli was also markedly mask selective. These findings offer strong support for the existence of both S- and S+ channels in the chromatic domain.


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