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D. Cao, B. B. Lee, R. Ennis; Receptive Field Structure of Primate Parasol Ganglion Cells Defined by Rod and Cone Inputs. Invest. Ophthalmol. Vis. Sci. 2010;51(13):5177.
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© ARVO (1962-2015); The Authors (2016-present)
We have previously shown that responses of parasol ganglion cells at different temporal frequencies with full field stimuli can be well predicted as a vector sum of rod and cone inputs (ARVO, 2009). Here, we extend this to the spatial domain to determine the receptive field structure of parasol ganglion cells defined by rod and cone inputs.
The responses of parafoveal ganglion cells were recorded from macaque retina using an in vivo preparation, as a function of spatial frequency (0 - 8 cpd) and mesopic light levels (0.565-565Td). Stimuli (33% Michelson contrast, 4.34 Hz) were of three modulation types: 1) isolated rod stimuli (only rod input was modulated), 2) isolated cone stimuli [only cone luminance (L+M) input was modulated], and 3) combined rod and cone stimuli (both rod and cone luminance inputs were modulated in phase). The spatial frequency tuning curves were fitted with a Gaussian or a DOG receptive field model.
Spatial frequency tuning curves with the isolated cone stimuli were variable in shape, with differing degrees of low-spatial frequency attenuation (band-pass to low-pass); but those with the isolated rod stimuli were always low-pass. Sizes of receptive field centers defined by cone input were stable, while the receptive field sizes defined by rod input remained unchanged or increased with decreasing light levels. When cells responded to both isolated rod and cone stimuli at the same light level, the receptive field center size defined by rod input was comparable or larger than size defined by cone input. The receptive field size and organization with the combined stimuli were comparable to those defined by cone input at the highest light level or those defined by rod input at the lowest light level.
Receptive fields defined by rod and cone inputs differ. The results are more consistent with receptive field structure defined by rod input being mediated by an AII amacrine pathway rather than through a secondary rod pathway derived from gap junctional coupling at low mesopic light levels.
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