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Lighting
Published in Sue Reed, Dino Pisaniello, Geza Benke, Principles of Occupational Health & Hygiene, 2020
More recently, a third set of photoreceptors has been found in the eye: a small population of intrinsically photosensitive retinal ganglion cells (ipRGCs). These cells contain melanopsin and are connected to the non-visual parts of the brain (Hattar et al., 2002). They show peak response to blue light with a wavelength of 460–480 nm. This action spectrum of ipRGCs is referred to as melanopic. It appears that melanopsin cells play a vital role in the entrainment of the body’s circadian rhythms by providing light input to the suprachiasmatic nucleus, located in the hypothalamus. The neurons in the hypothalamus control the body’s circadian rhythms.
Lighting
Published in Sue Reed, Dino Pisaniello, Geza Benke, Kerrie Burton, Principles of Occupational Health & Hygiene, 2020
More recently, a third set of photoreceptors has been found in the eye—a small population of intrinsically photosensitive retinal ganglion cells (ipRGCs). These cells contain melanopsin and are connected to the non-visual parts of the brain (Panda et al. 2005). They show peak response to blue light with a wavelength of 460–480 nm. It appears that melanopsin cells play a vital role in the entrainment of the body’s circadian rhythms by providing light input to the suprachiasmatic nucleus, located in the hypothalamus the neurons of which control the body’s circadian rhythms.
The Biological Basis of Non-Image-Forming Vision
Published in Agnieszka Wolska, Dariusz Sawicki, Małgorzata Tafil-Klawe, Visual and Non-Visual Effects of Light, 2020
Agnieszka Wolska, Dariusz Sawicki, Małgorzata Tafil-Klawe
According to the anatomic projection of ipRGCs, several non-visual effects of light mediated by melanopsin are described [Spitschan 2019a; Spitschan 2019b]: Pupil size regulation – strongly controlled by melanopsin dynamic pupil responses to light. All photoreceptors are involved in the control of pupil size [Spitchan 2019b].Melatonin suppression – a hormone produced by the pineal body during the night (“night hormone”). Melatonin production is suppressed by light via the retinohypothalamic pathway connecting ipRGCs to the suprachiasmatic nucleus. In some blind people, light suppresses melatonin secretion by ocular exposure to bright white light.Circadian phase shifting – night exposure to light – can shift the circadian rhythms of different biological processes, which are synchronized to the external light–dark cycle via the retinohypothalamic pathway. Illumination of the retina evokes excitatory postsynaptic potentials in a subpopulation of SCN neurons. These potentials are the result of glutamate release from the retinothalamic pathway and are mediated by inotropic and metabotropic glutamate receptors. Additionally, SCN-projecting ipRGCs synthetize pituitary adenylate cyclase-activating polypeptide (PACAP), which may act as a modulator of the glutamatergic input to the SCN [Sollars et al. 2015; Hannibal 2006]. Circadian phase-shifting is most spectacular for short wavelength light fitting melanopsin activation. In humans, cones seem to contribute to phase-shifting, and this contribution depends on the timing of the light exposure [Gooley et al. 2010; Spitschan 2019a]. It was also shown that rods may contribute to melatonin suppression [Vartanian et al. 2015].
Assessing the Effects of Polychromatic Light Exposure on Mood in Adults: A Systematic Review Contrasting α-opic Equivalent Daylight Illuminances
Published in LEUKOS, 2023
Ashley Nixon, Rebecca Robillard, Chloe Leveille, Alan B. Douglass, Meggan Porteous, Jennifer A. Veitch
In addition to stimulating visual perception, light influences many physiological and psychological processes, including cognition, sleep, and mood (Cajochen 2007; Duffy and Czeisler 2009; Golden et al. 2005). Light intensity, spectrum, duration, and timing are all thought to play a role in these effects (Prayag et al. 2019). Over recent years, researchers have revealed the prominent involvement of intrinsically photosensitive retinal ganglion cells (ipRGCs) in regulating circadian rhythms, melatonin secretion, and other biological processes. ipRGCs express melanopsin, a photopigment. They also receive synaptic input from other retinal photoreceptors (S-, M-, L-cones and rods) and contribute to diverse physiological and behavioral functions (Belenky et al. 2003; Brown et al. 2021; Dacey et al. 2005; Jusuf et al. 2007; Schmidt and Kofuji 2010; Wong et al. 2007). Direct pathways linking ipRGCs and various brain regions involved in emotional processing have also been found in both animal (Fernandez et al. 2018; Hattar et al. 2006; Huang et al. 2019; Legates et al. 2014) and human (Vandewalle et al. 2010; Weil et al. 2022) studies. While many studies focused on the melanopsin system, all photoreceptor systems interact closely and their relative contribution to the effects of light on mood in healthy humans remains poorly understood. Furthermore, because indoor lighting is typically polychromatic (i.e., white appearing and inclusive of many wavelengths), there is a need to move beyond monochromatic light comparisons, which are often used in studies that examine fundamental processes.
A Review of Human Physiological Responses to Light: Implications for the Development of Integrative Lighting Solutions
Published in LEUKOS, 2022
Céline Vetter, P. Morgan Pattison, Kevin Houser, Michael Herf, Andrew J. K. Phillips, Kenneth P. Wright, Debra J. Skene, George C. Brainard, Diane B. Boivin, Gena Glickman
The physiological effects of light are mediated by the eye in humans. Light entering the eye stimulates retinal photoreceptors that convert photic information into neuronal signals, which get transmitted via ganglion cells to various regions of the brain (Fig. 1). For many years, it was thought that there were only two classes of photoreceptors in the human eye—the rods and cones; however, another very different photoreceptor type was discovered in the mammalian eye about two decades ago. These retinal photoreceptors are specialized ganglion cells that contain the photopigment melanopsin and are intrinsically sensitive to light, and were therefore called intrinsically photosensitive retinal ganglion cells (ipRGCs) (Berson et al. 2002; Hattar et al. 2002; Provencio et al. 1998, 2000).
Syncing with the Sky: Daylight-Driven Circadian Lighting Design
Published in LEUKOS, 2021
Nathan Altenberg Vaz, Mehlika Inanici
ipRGCs contain the photopigment called melanopsin. They do not collect visual information. They respond to slow or still light for sustained periods, and they are insensitive to rapid light changes (Figueiro et al. 2008). In early studies by Brainard et al. (2001) and Thapan et al. (2001), spectral sensitivity is measured through melatonin suppression levels. Although other research show evidence that the rods and three types of cones might be contributing to nonvisual responses (Hattar et al. 2003; Lucas et al. 2003; Panda et al. 2002; Ruby et al. 2002), there has not been a wide consensus on a single standard curve to represent the integrated response of all five photoreceptors. Until a consensus is reached, Lucas et al. (2014) suggests to report photopic and melanopic illuminances, and this approach has been adopted in this paper.