Sensations from a single M-cone depend on the activity of surrounding S-cones

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 abberations were corrected with adaptive optics and its position was precisely tracked in real-time to compensate for natural movement. Subjects reported the color appearance of each spot. A majority of Land 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. Thus, what is seen when an M-cone is probed appears to depend on the relative activity of cones at other locations in the mosaic.

Effect of cone spectral topography on chromatic detection sensitivity

“…The coarse resolution of hue discrimination is reminiscent of earlier findings where only a small fraction (~1/3rd) of cones were associated with strong hue sensations [39,41], while the majority signaled achromatic sensations. That the cone mosaic readily serves the dual role of both high acuity spatial vision and red-green hue sensations indicates that the patterns of cone activity certainly encode sufficient information to retrieve wavelength and intensity independently from the environment.…”

“…The reliability of objective TCA measurements has been demonstrated in a few ways, in particular, Winter et al [36] used it to quantify the human eye's TCA and showed good agreement with previous theoretical estimates [37]. In addition, cone-targeted psychophysics undertaken in an AOSLO with eye-tracking employed the same objective TCA compensation and showed reliable percepts associated with single cone stimulation [38][39][40][41]. Given the reliability of TCA measurement and pupil monitoring, we can effectively eliminate it as a factor affecting our hue perception experiment.…”

Probing Computation in the Primate Visual System at Single-Cone Resolution

“…The inferences that could be made from the data described above are limited by fixational eye movements, which preclude knowledge of which cone was activated on any given trial. This limitation was overcome using real-time eye tracking in conjunction with adaptive optics (Sabesan et al 2016; see also Schmidt et al 2018). Subjects provided largely reliable color names in response to the repeated activation of individually targeted cones (Figure 4d).…”

Transverse chromatic offsets with pupil displacements in the human eye: sources of variability and methods for real-time correction

“…For example, adaptive optics scanning laser ophthalmoscope (AOSLO) based microperimetry [8] has been used to assess visual function in local areas of interest in diseased retinas [9]. Additionally, the capability for cone-targeted stimulus delivery with adaptive optics (AO) has made it possible to perform psychophysical experiments at the level of single cone photoreceptors [10][11][12][13].…”