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G Twig, H Levy, I Perlman; Spatial-Chromatic Interactions in C-type Horizontal cells of the Turtle Retina . Invest. Ophthalmol. Vis. Sci. 2002;43(13):3775.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Study the effects of the spatial patterns of the light stimuli upon color opponency of C-type horizontal cells. Methods: Intracellular recordings were conducted in the everted eyecup preparation of the turtle (Mauremys caspica) from 47 Red/Green (RGH) and 12 Yellow/Blue (YBH) C-type horizontal cells. The photoresponses were elicited in the dark-adapted state by long-wavelength (700nm for RGH; 600nm for YBH), «neutral» wavelength (the spectral region where response polarity reverses; 600-650nm for RGH cells and 540-580nm for YBH cells) and short-wavelength (540nm for RGH; 450nm for YBH) light stimuli of different spatial patterns. Results:(1) When a hyperpolarizing photoresponse was elicited by full field stimulation with a bright light stimulus of wavelength close to the neutral one, response polarity reversed when a small spot or a thin annular pattern were used for stimulation. (2) Reversal in response polarity could be also achieved by dimming the intensity of a neutral wavelength light stimulus, but maintaining full field illumination. (3) Mixtures of 700nm and 540nm were used to mimic neutral wavelength light stimuli and showed that dimming stimulus intensity could not account for the spatial effects upon response polarity. (4) The spatial properties (length constant) of the depolarizing and hyperpolarizing components of the light mixtures were found to differ in absolute values and in their dependency upon stimulus intensity. Conclusion: Response polarity of C-type horizontal cells in the turtle retina depends upon the relative activation of the antagonistic inputs to the cell. Differences in the lateral spread of the depolarizing and hyperpolarizing inputs can result in different relative contributions of the antagonistic inputs to the cells and therefore, affect response polarity. Thus, in C-type horizontal cells of the turtle retina response polarity depends upon the wavelength, intensity and the spatial configuration of the light stimulus.
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