Melanopsin photoreception contributes to human visual detection, temporal and colour processing

Andrew J Zele,Beatrix Feigl,Dingcai Cao,Michelle L Maynard,Prakash Adhikari

doi:10.1038/s41598-018-22197-w

Abstract

The visual consequences of melanopsin photoreception in humans are not well understood. Here we studied melanopsin photoreception using a technique of photoreceptor silent substitution with five calibrated spectral lights after minimising the effects of individual differences in optical pre-receptoral filtering and desensitising penumbral cones in the shadow of retinal blood vessels. We demonstrate that putative melanopsin-mediated image-forming vision corresponds to an opponent S-OFF L + M-ON response property, with an average temporal resolution up to approximately 5 Hz, and >10x higher thresholds than red-green colour vision. With a capacity for signalling colour and integrating slowly changing lights, melanopsin-expressing intrinsically photosensitive retinal ganglion cells maybe the fifth photoreceptor type for peripheral vision.

Highlights

Melanopsin photoreception in intrinsically photosensitive retinal ganglion cells has fundamental roles in light dependent, non-imaging forming functions such as circadian photoentrainment and pupil light responses[1,2,3,4]
Penumbral cones can be desensitised with temporal white noise that modulates the L-cone, M-cone, S-cone and rod photoreceptor excitations to provide a direct measure of melanopsin photoreception in humans
A known neurophysiological correlate of the intrinsically photosensitive retinal ganglion cells (ipRGC) response property in humans is the characteristic opponent melanopsin and S-cone pupil response[9,28] and we confirm that melanopsin inputs to the pupil response are unaffected by temporal white noise (Fig. 2a)

Summary

Introduction

Melanopsin photoreception in intrinsically photosensitive retinal ganglion cells (ipRGC) has fundamental roles in light dependent, non-imaging forming (i.e. non-visual) functions such as circadian photoentrainment and pupil light responses[1,2,3,4]. Functional magnetic resonance imaging studies in humans to high contrast melanopsin directed stimuli elicit a response in the visual cortex (area V1) which are associated with a brightening of visual percepts and distinct from the perceptual response to cone luminance directed stimuli[5]. To measure the perceptual correlate of melanopsin signalling in humans, the behavioural effects of melanopsin activation must be separated from visually detectable L- and M-cone signals arising through inadvertent stimulation of penumbral cones in the shadow of retinal blood vessels[10]. Conditions designed to modulate the melanopsin response, we estimate the visual detection threshold for melanopsin, its temporal contrast response and characterise its purported colour opponent response property

Methods

Results

Conclusion