Investigation of effect of retinal photoreceptor stimulations including melanopsin on brightness perception

Abstract

Brightness is perceived after photoreceptors are stimulated and signals from them are transmitted to the brain. Brightness perception differs depending on the wavelength. For example, yellow, a middle- wavelength light, is perceived brighter than blue light when the radiation intensity is the same. The direct heterochromatic brightness matching and the flicker photometry are widely known to measure brightness sensitivity. Although it is still unclear why there is a difference in spectral sensitivity between direct heterochromatic brightness matching and flicker photometry, the difference in brightness perception seems to be attributed to the temporal characteristics of physiological processes. The purpose of this study was to investigate the brightness perception caused by varying the amount of photoreceptor stimulations. In this study, we varied the amount of photoreceptor stimulation to clarify how each photoreceptor contributes to the brightness mechanism. It was found that observers perceived brighter as melanopsin stimulation increased according to psychometric function. The result was consistent with previous studies. In addition, we have found that there was a large difference in brightness when L- and M-cone stimulations varied whereas S-cone stimulation induced little change in brightness.