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Non-Visual Light Responses in Humans: Melanopsin and Cone Involvement.

Papamichael, Christiana. (2012) Non-Visual Light Responses in Humans: Melanopsin and Cone Involvement. Doctoral thesis, University of Surrey (United Kingdom)..

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Abstract

Melanopsin containing intrinsically photosensitive retinal ganglion cells (ipRGCs) are primarily sensitive blue light (~480 nm) irradiance detectors that mediate non-visual responses (NVRs) such as melatonin suppression by light and alteration of mood and alertness levels. Also, ipRGCs integrate inputs from rods and cones that are content dependent and enable fine-tuning of light-dependent NVR. The current thesis aimed to assess 1) whether simultaneous presentation of blue (max 479 nm) and red (max 627 nm) monochromatic light could alter human acute NVR to blue light alone (possible involvement of melanopsin bistability), 2) the dependency of the magnitude and dynamics of human acute NVRs on the irradiance, duration and total photon content of blue (max 479 nm), purple (max 437 nm) and green (max 555 nm) light stimuli to discern the contributions of melanopsin, S-cones and M/L-cones respectively, 3) the dependency of the magnitude and dynamics of human acute NVRs on the irradiance, duration and total photon content of blue-enriched polychromatic white light (17000 K). Young healthy male participants attended overnight in-laboratory sessions where lighting, caloric intake and posture where controlled. Pupils were dilated and light was administered via a sphere, with wavelength, irradiance and time of exposure being controlled. Blood sampling (for the assessment of melatonin suppression) and subjective mood and alertness scoring took place at regular intervals relative to the light exposure. Findings suggest that the blue light content is the primary determinant in bichromatic light pulses, the magnitude of NVRs is dependent on the interaction of the duration and irradiance of a light stimulus and that different NVRs are maximally sensitive to different wavelengths. The maximum NVR is not always achieved during the light exposure and is possible to utilise shorter dim 17000 K light pulses to produce similar results to brighter or longer exposures.

Item Type: Thesis (Doctoral)
Divisions : Theses
Authors : Papamichael, Christiana.
Date : 2012
Additional Information : Thesis (Ph.D.)--University of Surrey (United Kingdom), 2012.
Depositing User : EPrints Services
Date Deposited : 06 May 2020 14:23
Last Modified : 06 May 2020 14:28
URI: http://epubs.surrey.ac.uk/id/eprint/856153

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