October 2020
Volume 20, Issue 11
Open Access
Vision Sciences Society Annual Meeting Abstract  |   October 2020
V1 laminar spiking responses to binocular stimuli of varying contrast
Author Affiliations & Notes
  • Blake A. Mitchell
    Vanderbilt University
  • Kacie Dougherty
    Princeton University
  • Jacob A. Westerberg
    Vanderbilt University
  • Brock M. Carlson
    Vanderbilt University
  • Loic Daumail
    Vanderbilt University
  • Alexander Maier
    Vanderbilt University
  • Michele A. Cox
    University of Rochester
  • Footnotes
    Acknowledgements  NIH-NEI grant: 1R01EY027402-03
Journal of Vision October 2020, Vol.20, 860. doi:https://doi.org/10.1167/jov.20.11.860
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      Blake A. Mitchell, Kacie Dougherty, Jacob A. Westerberg, Brock M. Carlson, Loic Daumail, Alexander Maier, Michele A. Cox; V1 laminar spiking responses to binocular stimuli of varying contrast. Journal of Vision 2020;20(11):860. doi: https://doi.org/10.1167/jov.20.11.860.

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

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Abstract

Our forward-facing eyes provide two streams of visual information that merge into a single, coherent view. Psychophysical and anatomical studies have pointed to neurons in the primate primary visual cortex (V1) as playing an important role for this binocular combination. Yet, it remains unclear how V1 orchestrates the integration of two separate thalamocortical inputs into a combined binocular response. Previous neurophysiological and fMRI studies using binocular stimuli of similar and different contrast levels suggest that binocular combination in V1 is best explained by models incorporating sublinear summation of monocular inputs. However, we know little regarding the laminar specificity of these models. To address this question, macaque monkeys were trained to fixate while viewing static sinusoidal gratings of varying image contrast that were either presented monocularly or binocularly through a calibrated mirror stereoscope. Using linear multielectrode arrays, we recorded population spiking activity across the laminae of V1. Multiple electrophysical criteria were then used to group electrode contacts into three functionally-relevant groups corresponding to each the granular (middle), upper, and deep V1 laminae. We found binocular stimuli generally evoked stronger neural activity than their monocular counterparts for all contrast levels. A comparison between predicted and observed binocular responses revealed that linear summation failed to accurately account for binocular responses across V1 laminae (mean difference between predicted and observed = 12.2 ± 6.1). In contrast, the psychophysics-derived quadratic summation model that employs sublinear additivity of the two eyes’ inputs fit the observed data well overall (mean difference = -0.9 ± 3.5). The best fit was found in the deep layers (M = -0.1 ± 1.3) and the worst in the upper layers (M = -1.9 ± 5.1). These results correspond to similar observations of human fMRI and extend these findings to the level of population spiking responses across the laminar microcircuit of V1.

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