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Sunday, July 19 • 9:00pm - 10:00pm
P167: Modelling ipRGC-influenced light response on circadian phase, melatonin suppression and subjective sleepiness.

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Zoom Meeting :    https://uni-sydney.zoom.us/j/99904979215

Tahereh Tekieh
, Peter Robinson, Steven Lockley, Stephan McCloskey, M.s Zobaer, Svetlana Postnova

A physiologically-based model of arousal dynamics is extended to incorporate the spectral effects of light (as an input to the model) on the circadian rhythms, melatonin dynamics and subjective sleepiness. Doing this, photopic illuminance in the model is replaced with melanopic irradiance which, reflects the role of melanopsin, a photopigment expressed in ipRGCs (intrinsically photosensitive retinal ganglion cells). Melanopsin-expressing ipRGCs are the primary cells in retina mediating the effect of light to different non-visual related brain regions. Melanopsins are short wavelength sensitive and their main target is the circadian clock located in suprachiasmatic nuclei (SCN), with output signals regulating sleep/wake cycles, alertness, and hormone secretion. The melanopic irradiance is thus used as the light input to the model, which affects the dynamic circadian oscillator, melatonin (hormone produced in pineal gland) profile and sleepiness. The dynamic circadian oscillator is extended according to the melanopic irradiance definition and tested against experimental circadian phase dose- and phase-response data. The function which demonstrates melatonin suppression in presence of light re- calibrated against melatonin dose-response data for monochromatic and polychromatic light sources. A new light-dependent term is then introduced into the homeostatic weight component of subjective sleepiness to represent the direct effect of light. The new term responds dynamically to light and is calibrated against experimental data with different light spectrums. The model predictions are compared to a total of 14 experimental studies containing 26 data sets for 14 different spectral light profiles. The extended melanopic model shows an average reduction in prediction error relative to the model used prior. Overall, incorporating melanopic irradiance allows simulation of wavelength-dependent responses to light observed in experiments and explains most of the observations. Models demonstrating the effect of light on circadian dynamics, sleep, and sleepiness need to use ipRGC-influenced responses as a non-visual measure of light; e.g., melanopic irradiance, instead of the traditionally used illuminance based on the visual system.

Article DOI: 10.1111/jpi.12681
Article: Modelling melanopsin-mediated effects of light on circadian phase, melatonin suppression and subjective sleepiness
Journal: Journal of Pineal Research

avatar for Tahereh Tekieh

Tahereh Tekieh

Postdoctoral Research Fellow, The University of Sydney

Sunday July 19, 2020 9:00pm - 10:00pm CEST
Slot 03