Modelling the spectral sensitivity of the human circadian system

Abstract

It is now well established that the spectral, spatial, temporal and absolute sensitivities of the human circadian system are very different from those of the human visual system. Although qualitative comparisons between the human circadian and visual systems can be made, there still remains some uncertainty in quantitatively predicting exactly how the circadian system will respond to different light exposures reaching the retina. This paper discusses attempts to model the spectral sensitivity of the circadian system. Each of the models discussed here varies in terms of its complexity and its consideration of retinal neuroanatomy and neurophysiology. Future testing to validate or improve any of these computational models will require a targeted hypothesis, as well as a suitably high level of experimental control before one model can be rejected in favour of another. Until specific hypotheses are formulated and tested, it would be premature to recommend international acceptance of any model or system of circadian photometry.

Ground-based hyperspectral analysis of the urban nightscape

“…Although there are still considerable uncertainties in this field, the basic mechanisms of the interaction of artificial light at night with the human physiology are progressively being unveiled (see the review in Bonmati-Carrion et al, 2014). A comprehensive model describing the effects of the nocturnal exposure to light on the production of the hormone melatonin (MLT) has been proposed by Rea et al (2005Rea et al ( , 2010Rea et al ( , 2012. This model provides quantitative predictions of the percentage of acute MLT suppression in blood (CS), under some definite experimental lighting conditions.…”

“…This radiance distribution allows the assessment of glare and light cluttering. It is also instrumental for computing the spectral irradiance in a plane tangent to the human corneal vertex for arbitrary gaze directions, which is 5 the primary input for evaluating the physiological effects of light at night by means of suitable phototransduction models (CIE, 2015;Rea et al 2005Rea et al , 2010Rea et al , 2012. The vertical irradiance on window panes allows, in turn, to quantify the severity of light trespass effects.…”

Color science of nanocrystal quantum dots for lighting and displays

“…According to Rea, melatonin suppression is affected collectively by rods, cones, and melanopsin [ 42 ], while Gall employs a simpler method [ 43 ]. Today, there is not enough data to falsify either of these models [ 44 ].…”

A Working Threshold for Acute Nocturnal Melatonin Suppression from “White” Light Sources used in Architectural Applications

“…Retinal exposure to short-wavelength light of sufficiently high level and long duration will suppress nocturnal melatonin synthesis by the pineal gland via signal from the SCN; nocturnal melatonin suppression is an orthodox marker for circadian system stimulation by light [5][6][7][8][9][10].…”

“…Posture [11], photic history [12,13], biomarker type, methods for calculating acute melatonin suppression, the pulsatic nature of melatonin production [14], individual differences in preretinal filtering [15], and diet [16] are some of the reasons why it is difficult to define a value that might be taken as "the" threshold amount of light needed to suppress nocturnal melatonin. It is possible, however, to make predictions of the potential effectiveness of different light sources for reaching a criterion amount of nocturnal melatonin suppression using the model proposed by Rea et al [6][7]. Consistent with published evidence from neurophysiology and neuro-anatomy, and from empirical data on light-induced nocturnal melatonin suppression in humans [8][9][10], the model incorporates the photopigment melanopsin contained in the Intrinsically-Photosensitive Retinal Ganglion Cells (ipRGCs) [17], as well as the photopigments in rods and cones.…”