June 2022
Volume 63, Issue 7
Open Access
ARVO Annual Meeting Abstract  |   June 2022
Amblyopia Impacts on Activity within Human V2/V3 Thin and Thick Stripes during Binocular Summation
Author Affiliations & Notes
  • Shahin Nasr
    Radiology, Massachusetts General Hospital, Boston, Massachusetts, United States
    Radiology, Harvard Medical School, Boston, Massachusetts, United States
  • Bryan Kennedy
    Radiology, Massachusetts General Hospital, Boston, Massachusetts, United States
  • Jan Skerswetat
    Psychology, Northeastern University, Boston, Massachusetts, United States
  • Nicolas Aycardi
    Psychology, Northeastern University, Boston, Massachusetts, United States
  • Amanda Nabasaliza
    Radiology, Massachusetts General Hospital, Boston, Massachusetts, United States
    Ophthalmology, Boston Children's Hospital, Boston, Massachusetts, United States
  • Roger BH Tootell
    Radiology, Massachusetts General Hospital, Boston, Massachusetts, United States
    Radiology, Harvard Medical School, Boston, Massachusetts, United States
  • Peter J Bex
    Psychology, Northeastern University, Boston, Massachusetts, United States
  • David G Hunter
    Ophthalmology, Harvard Medical School, Boston, Massachusetts, United States
    Ophthalmology, Boston Children's Hospital, Boston, Massachusetts, United States
  • Footnotes
    Commercial Relationships   Shahin Nasr None; Bryan Kennedy None; Jan Skerswetat PerZeption Inc., Code O (Owner), FInD Method, Code P (Patent); Nicolas Aycardi None; Amanda Nabasaliza None; Roger Tootell None; Peter Bex PerZeption Inc., Code O (Owner), FInD Method, Code P (Patent); David Hunter Rebion, Luminopia, Quanterix, Code I (Personal Financial Interest), Rebion, Code O (Owner), Rebion, Code P (Patent), Rebion, Code R (Recipient), Rebion, Luminopia, Code S (non-remunerative)
  • Footnotes
    Support  NIH Grant R01EY030434 and NIH Grant R01EY029713
Investigative Ophthalmology & Visual Science June 2022, Vol.63, 2290. doi:
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      Shahin Nasr, Bryan Kennedy, Jan Skerswetat, Nicolas Aycardi, Amanda Nabasaliza, Roger BH Tootell, Peter J Bex, David G Hunter; Amblyopia Impacts on Activity within Human V2/V3 Thin and Thick Stripes during Binocular Summation. Invest. Ophthalmol. Vis. Sci. 2022;63(7):2290.

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

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Abstract

Purpose : In normally-sighted individuals, visual acuity benefits from binocular summation. However, this effect is weakened in amblyopic individuals, especially for high spatial frequency (SF) stimuli (Pardhan and Gilchrist, 1992). To clarify the underlying disorder, we examined the function of thick and thin stripes in human V2 (and V3) during monocular and binocular perception. In normally sighted individuals, these stripes respond differentially to low- vs. high-SF components (Tootell and Nasr, 2017).

Methods : Six strabismic and five anisometropic (best-corrected visual acuity in the amblyopic eye 20/60 to 20/300) individuals, aged 19-55 years old, participated in this study. Using high-resolution fMRI (7T; voxel size = 1 mm isotropic), we localized thin and thick stripes across V2/V3 (Figure 1A). Then, we measured the activity within these stripes as subjects were presented with high (99%) and low (5%) contrast gratings of 0.1–5.8 cycle/deg., either monocularly or binocularly.

Results : For monocularly presented high-contrast stimuli, thin and thick stripes showed a preference for high-SF (Figure 1B) and low-SF (Figure 1C), respectively. This preference did not vary based on the stimulated eye. When presented binocularly, low-SF (but not high-SF) gratings evoked a significantly stronger response, compared to when the same stimuli were presented monocularly (p<0.01). When normalized relative to the averaged response, this effect was significantly stronger in thin compared to thick stripes (p<0.05).
For low-contrast stimuli, high-SF gratings evoked a stronger response when presented to fellow- compared to amblyopic-eye (Figure 1D-E). However, only the response to low-SF gratings benefited from binocular summation.

Conclusions : In amblyopic individuals, the impact of binocular summation is limited to the response to low-SF gratings and appeared to be stronger in V2/V3 thin (relative to thick) stripes.

This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.

 

Panel A shows V2/V3 thin and thick stripes in one amblyopic individual localized based on their selectivity for color and motion, respectively (Tootell and Nasr, 2021). Panels B-E show the activity evoked by high and low contrast gratings in V2 thin and thick stripes. In both contrast levels, binocular summation remained limited to the response to low-SF stimuli. Activity measured in V3 showed the same effect. Error bars show one standard error of mean.

Panel A shows V2/V3 thin and thick stripes in one amblyopic individual localized based on their selectivity for color and motion, respectively (Tootell and Nasr, 2021). Panels B-E show the activity evoked by high and low contrast gratings in V2 thin and thick stripes. In both contrast levels, binocular summation remained limited to the response to low-SF stimuli. Activity measured in V3 showed the same effect. Error bars show one standard error of mean.

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