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MiYoung Kwon, Rong Liu; Contribution of retinal ganglion cell density to the non-uniform spatial integration across the visual field. Invest. Ophthalmol. Vis. Sci. 2019;60(9):3909.
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© ARVO (1962-2015); The Authors (2016-present)
The integration of visual information over spaceis a critical step in human pattern recognition. Regardless of whether it is for detecting luminance contrast or for recognizing objects in a cluttered scene, the position of the target in the visual field governs the size of a window within which visual information is integrated. Yet, the precise mechanism underpinning this integration process remains unclear. Here we examine whether the sampling density of retinal ganglion cells (RGCs) serves as an important constraint on cortical integration process.
Twenty one normally sighted subjects were recruited (mean age ± SD = 22.62 ± 3.81; mean visual acuity = -0.09 ± 0.09 logMAR for the tested eye). For each subject, the extent of spatial integration for luminance detection (Ricco’s area) and object recognition (crowding zone) was measured at 7 different visual field locations. In order to obtain the RGC density of the human retina, we used Drasdo et al.’s (2007) formula based on histological data of the human adult retina. The number of RGCs underlying Ricco’s area or crowding zone was estimated by computing the product of Ricco’s area (or crowding zone) and RGC density for a given target location.
We found that once the sampling density of RGCs was taken into account, the variation in the extent of spatial integration across the visual field became less pronounced for both Ricco’s area and crowding zone. The relative contribution of the underlying RGC density to the variation in the spatial extent was found to be about 74% to up to 98%. The known properties of crowding: eccentricity-dependency, radial-tangential anisotropy, upper-lower visual field asymmetry, and inner-outer asymmetry, arised from the RGC mosaic when crowding zone was simulated across the visual field following the fixed number of RGCs rule.
Our empirical data combined with the simulation results of computational models suggest that a fixed number of RGCs may subserve cortical integration of visual input, independent of the visual-field location. Our findings further support the view that the topographic distribution of the RGCs largely underlies cortical representation of the visual space.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
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