September 2021
Volume 21, Issue 9
Open Access
Vision Sciences Society Annual Meeting Abstract  |   September 2021
Revealing Differential Mechanisms of Absolute vs. Relative Disparity Encoding in Human Extrastriate Visual Cortex and Impacts of Amblyopia on Them
Author Affiliations & Notes
  • Shahin Nasr
    Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital
    Department of Radiology, Harvard Medical School
  • Bryan Kennedy
    Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital
  • Amanda Nabasaliza
    Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital
    Department of Ophthalmology, Boston Children’s Hospital
  • Peter Bex
    Department of Psychology, Northeastern University
  • David G. Hunter
    Department of Ophthalmology, Boston Children’s Hospital
    Department of Ophthalmology, Harvard Medical School
  • Roger B.H. Tootell
    Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital
    Department of Radiology, Harvard Medical School
  • Footnotes
    Acknowledgements  This work was supported by NIH NEI (grants R01EY026881 and R01EY030434), and by the MGH/HST Athinoula A. Martinos Center for Biomedical Imaging. Crucial resources were made available by a NIH Shared Instrumentation Grant S10-RR019371.
Journal of Vision September 2021, Vol.21, 1986. doi:https://doi.org/10.1167/jov.21.9.1986
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      Shahin Nasr, Bryan Kennedy, Amanda Nabasaliza, Peter Bex, David G. Hunter, Roger B.H. Tootell; Revealing Differential Mechanisms of Absolute vs. Relative Disparity Encoding in Human Extrastriate Visual Cortex and Impacts of Amblyopia on Them. Journal of Vision 2021;21(9):1986. doi: https://doi.org/10.1167/jov.21.9.1986.

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

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Abstract

Background: Absolute and relative disparity cues are crucial for coarse and fine depth encoding, respectively. In human and non-human primates (NHPs), relative disparity cues are preferentially encoded within thick-type cortical columns, distributed within extrastriate visual cortex. In NHPs, electrophysiological evidence for absolute disparity encoding is limited to areas V1 and MT. However, neural mechanisms underlying absolute disparity encoding in human extrastriate cortex are largely unknown. This information is crucial in terms of defining the cortical sites affected by amblyopia, a developmental disorder caused by disruption of symmetric binocular visual input early in life, with significant impact on stereopsis. Methods: We used high resolution fMRI (7T) to test the response to absolute vs. relative disparity in seven individuals with normal vision, plus five amblyopic (3 strabismic and 2 anisometropic) individuals with impaired stereopsis (stereoacuity >250 arc sec; randot test). Stimuli were generated using random dot stereograms. In each individual, motion- and color-selective clusters were localized within areas V2, V3 and V3A based on independent scans (see also Kennedy et al. abstract). Results: In addition to area MT, absolute disparity evoked a significant response within V3 and V3A (but not V2) motion-selective clusters. This activity was significantly stronger than the response to relative disparity. Outside motion-selective clusters, those clusters that showed a significant response to relative disparity showed a weaker response to absolute disparity. Color-selective clusters did not show any significant response to either relative or absolute disparity. Motion-selective clusters were detected across V3 and V3A in amblyopic (as in non-amblyopic) individuals (see also Kennedy et al.). However, in amblyopic individuals, we did not find any significant response to absolute/relative disparity within/outside motion-selective clusters. Conclusion: Absolute and relative disparity are encoded within different neuronal clusters across areas V3 and V3A. Development of absolute and relative disparity encoding mechanisms are impaired by amblyopia.

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