A quantitative analysis of the contribution of melanopsin to brightness perception

Abstract

In the retina, intrinsically photosensitive retinal ganglion cells (ipRGCs) which express photopigment melanopsin have been identified as photoreceptors which differ from cones and rods. It has been established that such melanopsin-expressing RGCs are involved in the circadian photo-entrainment and pupillary light reflexes. An additional projection from ipRGCs to the lateral geniculate nucleus has been identified, which indicates the association of ipRGCs with visual perception induced by the image-forming pathway. Reportedly, ipRGCs modulate brightness perception but quantitative analysis of brightness perception involving melanopsin and cones-based signals has not been elucidated. We conducted brightness perception experiments that involved melanopsin using a novel projector with six primary colors and formulated the results for melanopsin and cone stimuli. The white visual stimuli (5 degrees in size) that we used had a single xy-chromaticity values but melanopsin stimuli were modulated by designing different spectral distributions. Perceived brightness was measured using a magnitude estimation method at several luminance levels in the near periphery (7 degrees). Additionally, pupil diameter was measured for estimating the intensity of visual stimuli on the retina. The results showed that the perceived brightness of a white visual stimulus with different spectral distributions can be described by a summation of the nearly linear melanopsin response and the non-linear cone response with weighted coefficients, and the contribution ratio of melanopsin in brightness perception increased to 50% and more with increasing visual stimulus. These suggest that melanopsin signals play a crucial role in the estimation of the absolute intensity of the light environment by obtaining absolute brightness information even when cones are adapted by light.

Prediction accuracy of L- and M-cone based human pupil light models

“…Thus, the underlying assumption of existing models that the pupil light response is controlled via an achromatic channel consisting of an additive combination of L and M-cones is obsolete. This is mainly due to the discovery of melanopsin expressing intrinsically photosensitive ganglion cells (ipRGCs) [32][33][34][35][36][37] in the inner retina which contributed fundamentally to the understanding of visual processing 34,[38][39][40][41][42] , form vision 43 , brightness perception [44][45][46][47][48][49][50] , circadian photoentrainment 37,[51][52][53] and pupil light response [54][55][56][57] . There are six different subtypes 58,59 of ipRGCs projecting to the olivary pretectal nucleus 36,41 (OPN), the dorsal lateral geniculate nucleus 43,60,61 (LGN) and the suprachiasmatic nucleus 42,62 (SCN) of the hypothalamus.…”

Melanopsin Contributions to Human Brightness Perception

“…Similarly, a blind person lacking functional classical photoreceptors can detect a light step. The apparent brightness is enhanced as stimulation of melanopsin increases in humans [3][4][5]. Although these results support the fact that melanopsin cells play an important role in the conventional visual pathway in humans, their functional role remains unclear.…”

Perfect appearance match between self-luminous and surface colors can be performed with isomeric spectra

“…The second possibility is the influence of rods and ipRGCs in color appearance. It has been shown that ipRGCs have a visual impact on peripheral vision 39 – 43 . However, the subtypes of ipRGCs, M2 and M4, which innervate dLGN 44 , also exist in the fovea 45 , suggesting that ipRGCs affect color perception even in the fovea.…”