Abstract
Color vision requires the activity of cone photoreceptors to be compared in post-receptoral circuitry. Decades of psychophysical measurements have quantified the nature of these comparative interactions on a coarse scale. How such findings generalize to a cellular scale remains unclear. To answer that question, we quantified the influence of surrounding light on the appearance of spots targeted to individual cones. The eye’s aberrations were corrected with adaptive optics and retinal position was precisely tracked in real-time to compensate for natural movement. Subjects reported the color appearance of each spot. A majority of L-and M-cones consistently gave rise to the sensation of white, while a smaller group repeatedly elicited hue sensations. When blue sensations were reported they were more likely mediated by M- than L-cones. Blue sensations were elicited from M-cones against a short-wavelength light that preferentially elevated the quantal catch in surrounding S-cones, while stimulation of the same cones against a white background elicited green sensations. In one of two subjects, proximity to S-cones increased the probability of blue reports when M-cones were probed. We propose that M-cone increments excited both green and blue opponent pathways, but the relative activity of neighboring cones favored one pathway over the other.
Highlights
Background condition and colorimetryBackgrounds were set with an external projector in Maxwellian view
Most L-cones fell along the white-red axis, with only occasional blue responses. These results demonstrate the substantial influence the relative activity of S-cones has on the color appearance of small spots of light
Subjects reported blue sensations on 21% of trials, which was consistent with color assimilation
Summary
Background condition and colorimetryBackgrounds were set with an external projector in Maxwellian view. In order to measure the chromaticity and luminance of the overall white and blue backgrounds engendered by these multiple sources, a patch the same size as and adjacent to the background was generated with the external projector. The subject was given control over the chromaticity and luminance of the adjacent patch and asked to achieve a match in hue and brightness to the background. This procedure was carried out two times. The chromaticity of the blue background was 0.16, 0.15 in CIE 1931 xy space and the luminance was 38 cd m−2. The quantal catches were transformed into a MacLeod-Boynton color space constructed from the Stockman & Sharpe fundamentals[33]
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