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Adhikari P, Uprety S, Feigl B, Zele AJ. Melanopsin-mediated amplification of cone signals in the human visual cortex. Proc Biol Sci 2024; 291:20232708. [PMID: 38808443 DOI: 10.1098/rspb.2023.2708] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2023] [Accepted: 05/02/2024] [Indexed: 05/30/2024] Open
Abstract
The ambient daylight variation is coded by melanopsin photoreceptors and their luxotonic activity increases towards midday when colour temperatures are cooler, and irradiances are higher. Although melanopsin and cone photoresponses can be mediated via separate pathways, the connectivity of melanopsin cells across all levels of the retina enables them to modify cone signals. The downstream effects of melanopsin-cone interactions on human vision are however, incompletely understood. Here, we determined how the change in daytime melanopsin activation affects the human cone pathway signals in the visual cortex. A 5-primary silent-substitution method was developed to evaluate the dependence of cone-mediated signals on melanopsin activation by spectrally tuning the lights and stabilizing the rhodopsin activation under a constant cone photometric luminance. The retinal (white noise electroretinogram) and cortical responses (visual evoked potential) were simultaneously recorded with the photoreceptor-directed lights in 10 observers. By increasing the melanopsin activation, a reverse response pattern was observed with cone signals being supressed in the retina by 27% (p = 0.03) and subsequently amplified by 16% (p = 0.01) as they reach the cortex. We infer that melanopsin activity can amplify cone signals at sites distal to retinal bipolar cells to cause a decrease in the psychophysical Weber fraction for cone vision.
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Affiliation(s)
- Prakash Adhikari
- Centre for Vision and Eye Research, Queensland University of Technology (QUT), Brisbane, Queensland 4059, Australia
| | - Samir Uprety
- Centre for Vision and Eye Research, Queensland University of Technology (QUT), Brisbane, Queensland 4059, Australia
| | - Beatrix Feigl
- Centre for Vision and Eye Research, Queensland University of Technology (QUT), Brisbane, Queensland 4059, Australia
- School of Biomedical Sciences, Queensland University of Technology (QUT), Brisbane, Queensland 4059, Australia
- Queensland Eye Institute, Brisbane, Queensland 4101, Australia
| | - Andrew J Zele
- Centre for Vision and Eye Research, Queensland University of Technology (QUT), Brisbane, Queensland 4059, Australia
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Barrionuevo PA, Sandoval Salinas ML, Fanchini JM. Are ipRGCs involved in human color vision? Hints from physiology, psychophysics, and natural image statistics. Vision Res 2024; 217:108378. [PMID: 38458004 DOI: 10.1016/j.visres.2024.108378] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2023] [Revised: 02/09/2024] [Accepted: 02/25/2024] [Indexed: 03/10/2024]
Abstract
Human photoreceptors consist of cones, rods, and melanopsin-expressing intrinsically photosensitive retinal ganglion cells (ipRGCs). First studied in circadian regulation and pupillary control, ipRGCs project to a variety of brain centers suggesting a broader involvement beyond non-visual functions. IpRGC responses are stable, long-lasting, and with a particular codification of photoreceptor signals. In comparison with the transient and adaptive nature of cone and rod signals, ipRGCs' signaling might provide an ecological advantage to different attributes of color vision. Previous studies have indicated melanopsin's influence on visual responses yet its contribution to color perception in humans remains debated. We summarized evidence and hypotheses (from physiology, psychophysics, and natural image statistics) about direct and indirect involvement of ipRGCs in human color vision, by first briefly assessing the current knowledge about the role of melanopsin and ipRGCs in vision and codification of spectral signals. We then approached the question about melanopsin activation eliciting a color percept, discussing studies using the silent substitution method. Finally, we explore various avenues through which ipRGCs might impact color perception indirectly, such as through involvement in peripheral color matching, post-receptoral pathways, color constancy, long-term chromatic adaptation, and chromatic induction. While there is consensus about the role of ipRGCs in brightness perception, confirming its direct contribution to human color perception requires further investigation. We proposed potential approaches for future research, emphasizing the need for empirical validation and methodological thoroughness to elucidate the exact role of ipRGCs in human color vision.
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Affiliation(s)
- Pablo A Barrionuevo
- Allgemeine Psychologie, Justus-Liebig-Universität Gießen, Germany; Instituto de Investigación en Luz, Ambiente y Visión (ILAV), CONICET - Universidad Nacional de Tucumán, Argentina.
| | - María L Sandoval Salinas
- Instituto de Investigación en Luz, Ambiente y Visión (ILAV), CONICET - Universidad Nacional de Tucumán, Argentina; Instituto de Investigaciones de Biodiversidad Argentina (PIDBA), Facultad de Ciencias Naturales e Instituto Miguel Lillo, Universidad Nacional de Tucumán, Argentina
| | - José M Fanchini
- Instituto de Investigación en Luz, Ambiente y Visión (ILAV), CONICET - Universidad Nacional de Tucumán, Argentina; Departamento de Luminotecnia, Luz y Visión, Facultad de Ciencias Exactas y Tecnología, Universidad Nacional de Tucumán, Argentina
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Chien SE, Yeh SL, Yamashita W, Tsujimura SI. Enhanced human contrast sensitivity with increased stimulation of melanopsin in intrinsically photosensitive retinal ganglion cells. Vision Res 2023; 209:108271. [PMID: 37331304 DOI: 10.1016/j.visres.2023.108271] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2022] [Revised: 05/15/2023] [Accepted: 05/22/2023] [Indexed: 06/20/2023]
Abstract
The intrinsically photosensitive retinal ganglion cells (ipRGCs) are known to serve non-image-forming functions, such as photoentrainment of the circadian rhythm and pupillary light reflex. However, how they affect human spatial vision is largely unknown. The spatial contrast sensitivity function (CSF), which measures contrast sensitivity as a function of spatial frequency, was used in the current study to investigate the function of ipRGCs in pattern vision. To compare the effects of different background lights on the CSF, we utilized the silent substitution technique. We manipulated the stimulation level of melanopsin (i.e., the visual pigment of ipRGCs) from the background light while keeping the cone stimulations constant, or vice versa. We conducted four experiments to measure the CSFs at various spatial frequencies, eccentricities, and levels of background luminance. Results showed that melanopsin stimulation from the background light enhances spatial contrast sensitivity across different eccentricities and luminance levels. Our finding that melanopsin contributes to CSF, combined with the receptive field analysis, suggests a role for the magnocellular pathway and challenges the conventional view that ipRGCs are primarily responsible for non-visual functions.
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Affiliation(s)
- Sung-En Chien
- Department of Psychology, National Taiwan University, Taipei 10617, Taiwan; Ganzin Technology Inc., New Taipei City 23141, Taiwan
| | - Su-Ling Yeh
- Department of Psychology, National Taiwan University, Taipei 10617, Taiwan; Graduate Institute of Brain and Mind Sciences, National Taiwan University, Taipei 10617, Taiwan; Neurobiology and Cognitive Science Center, National Taiwan University, Taipei 10617, Taiwan; Center for Advanced Studies in the Behavioral Sciences, Stanford University, Stanford, CA 94305, USA.
| | - Wakayo Yamashita
- Faculty of Science and Engineering, Kagoshima University, Kagoshima 890-0065, Japan
| | - Sei-Ichi Tsujimura
- Faculty of Science and Engineering, Kagoshima University, Kagoshima 890-0065, Japan; Faculty of Design and Architecture, Nagoya City University, Nagoya 467-8501, Japan.
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Nugent TW, Carter DD, Uprety S, Adhikari P, Feigl B, Zele AJ. Protocol for isolation of melanopsin and rhodopsin in the human eye using silent substitution. STAR Protoc 2023; 4:102126. [PMID: 36892996 PMCID: PMC10011832 DOI: 10.1016/j.xpro.2023.102126] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2022] [Revised: 12/13/2022] [Accepted: 02/02/2023] [Indexed: 03/09/2023] Open
Abstract
Melanopsin-mediated visual and non-visual functions are difficult to study in vivo. To isolate melanopsin responses, non-standard light stimulation instruments are required, with at least as many primaries as photoreceptor classes in the eye. In this protocol, we describe the physical light calibrations of the display instrumentation, control of stimulus artefacts, and correction of individual between-eye differences in human observers. The protocol achieves complete photoreceptor silent substitution in psychophysical, pupillometry, and electroretinographic experiments for probing melanopsin, rod, and cone function. For complete details on the use and execution of this protocol, please refer to Uprety et al. (2022).1.
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Affiliation(s)
- Thomas W Nugent
- Centre for Vision and Eye Research, Queensland University of Technology (QUT), Brisbane, QLD 4059, Australia; School of Optometry and Vision Science, Queensland University of Technology (QUT), Brisbane, QLD 4059, Australia
| | - Drew D Carter
- Centre for Vision and Eye Research, Queensland University of Technology (QUT), Brisbane, QLD 4059, Australia; School of Optometry and Vision Science, Queensland University of Technology (QUT), Brisbane, QLD 4059, Australia
| | - Samir Uprety
- Centre for Vision and Eye Research, Queensland University of Technology (QUT), Brisbane, QLD 4059, Australia; School of Optometry and Vision Science, Queensland University of Technology (QUT), Brisbane, QLD 4059, Australia
| | - Prakash Adhikari
- Centre for Vision and Eye Research, Queensland University of Technology (QUT), Brisbane, QLD 4059, Australia; School of Optometry and Vision Science, Queensland University of Technology (QUT), Brisbane, QLD 4059, Australia
| | - Beatrix Feigl
- Centre for Vision and Eye Research, Queensland University of Technology (QUT), Brisbane, QLD 4059, Australia; School of Biomedical Sciences, Queensland University of Technology (QUT), Brisbane, QLD 4059, Australia; Queensland Eye Institute, Brisbane, QLD 4101, Australia
| | - Andrew J Zele
- Centre for Vision and Eye Research, Queensland University of Technology (QUT), Brisbane, QLD 4059, Australia; School of Optometry and Vision Science, Queensland University of Technology (QUT), Brisbane, QLD 4059, Australia.
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Portengen BL, Porro GL, Imhof SM, Naber M. The Trade-Off Between Luminance and Color Contrast Assessed With Pupil Responses. Transl Vis Sci Technol 2023; 12:15. [PMID: 36622687 PMCID: PMC9838585 DOI: 10.1167/tvst.12.1.15] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2022] [Accepted: 12/06/2022] [Indexed: 01/10/2023] Open
Abstract
Purpose A scene consisting of a white stimulus on a black background incorporates strong luminance contrast. When both stimulus and background receive different colors, luminance contrast decreases but color contrast increases. Here, we sought to characterize the pattern of stimulus salience across varying trade-offs of color and luminance contrasts by using the pupil light response. Methods Three experiments were conducted with 17, 16, and 17 healthy adults. For all experiments, a flickering stimulus (2 Hz; alternating color to black) was presented superimposed on a background with a complementary color to the stimulus (i.e., opponency colors in human color perception: blue and yellow for Experiment 1, red and green for Experiment 2, and equiluminant red and green for Experiment 3). Background luminance varied between 0% and 45% to trade off luminance and color contrast with the stimulus. By comparing the locus of the optimal trade-off between color and luminance across different color axes, we explored the generality of the trade-off. Results The strongest pupil responses were found when a substantial amount of color contrast was present (at the expense of luminance contrast). Pupil response amplitudes increased by 15% to 30% after the addition of color contrast. An optimal pupillary responsiveness was reached at a background luminance setting of 20% to 35% color contrast across several color axes. Conclusions These findings suggest that a substantial component of pupil light responses incorporates color processing. More sensitive pupil responses and more salient stimulus designs can be achieved by adding subtle levels of color contrast between stimulus and background. Translational Relevance More robust pupil responses will enhance tests of the visual field with pupil perimetry.
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Affiliation(s)
- Brendan L. Portengen
- Department of Ophthalmology, University Medical Center Utrecht, Utrecht, The Netherlands
- Department of Experimental Psychology, Helmholtz Institute, Utrecht University, Utrecht, The Netherlands
| | - Giorgio L. Porro
- Department of Ophthalmology, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Saskia M. Imhof
- Department of Ophthalmology, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Marnix Naber
- Department of Experimental Psychology, Helmholtz Institute, Utrecht University, Utrecht, The Netherlands
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Nugent TW, Zele AJ. A five-primary Maxwellian-view display for independent control of melanopsin, rhodopsin, and three-cone opsins on a fine spatial scale. J Vis 2022; 22:20. [DOI: 10.1167/jov.22.12.20] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Affiliation(s)
- Thomas W. Nugent
- Center for Vision and Eye Research, Queensland University of Technology (QUT), Brisbane, QLD, Australia
| | - Andrew J. Zele
- Center for Vision and Eye Research, Queensland University of Technology (QUT), Brisbane, QLD, Australia
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Cormenzana Méndez I, Martín A, O'Donell B, Cao D, Barrionuevo PA. Temporal integration of rod signals in luminance and chromatic pathways. JOURNAL OF THE OPTICAL SOCIETY OF AMERICA. A, OPTICS, IMAGE SCIENCE, AND VISION 2022; 39:1782-1793. [PMID: 36215550 DOI: 10.1364/josaa.462581] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/28/2022] [Accepted: 08/13/2022] [Indexed: 06/16/2023]
Abstract
We assessed how rod excitation (R) affects luminance (L + M + S) and chromatic [L/(L + M)] reaction times (RTs). A four-primary display based on the overlapped images of two spectrally modified monitors, which allowed specific or combined [L + M + S + R, L/(L + M) + R] photoreceptor stimulation, was used to present a C-target stimulus differing from the background only by the selected stimulation. For the luminance pathway, rod input increased RTs, suggesting a suppressive rod-cone interaction. The responses of the chromatic pathway were faster when rods were involved, suggesting a major role of rods in mesopic color perception.
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Uprety S, Adhikari P, Feigl B, Zele AJ. Melanopsin photoreception differentially modulates rod-mediated and cone-mediated human temporal vision. iScience 2022; 25:104529. [PMID: 35754721 PMCID: PMC9218364 DOI: 10.1016/j.isci.2022.104529] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2022] [Revised: 05/04/2022] [Accepted: 05/30/2022] [Indexed: 11/17/2022] Open
Abstract
To evaluate the nature of interactions between visual pathways transmitting the slower melanopsin and faster rod and cone signals, we implement a temporal phase summation paradigm in human observers using photoreceptor-directed stimuli. We show that melanopsin stimulation interacts with and alters both rod-mediated and cone-mediated vision regardless of whether it is perceptually visible or not. Melanopsin-rod interactions result in either inhibitory or facilitatory summation depending on the temporal frequency and photoreceptor pathway contrast sensitivity. Moreover, by isolating rod vision, we reveal a bipartite intensity response property of the rod pathway in photopic lighting that extends its operational range at lower frequencies to beyond its classic saturation limits but at the expense of attenuating sensitivity at higher frequencies. In comparison, melanopsin-cone interactions always lead to facilitation. These interactions can be described by linear or probability summations and potentially involve multiple intraretinal and visual cortical pathways to set human visual contrast sensitivity. Melanopsin ipRGCs support vision independent of the rod and cone signals Rod pathways mediate robust visual responses in daylight Temporal contrast sensitivity is contingent on the melanopsin excitation level Visual performance is collectively regulated by melanopsin, rod and cone pathways
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Affiliation(s)
- Samir Uprety
- Centre for Vision and Eye Research, Queensland University of Technology (QUT), Brisbane, QLD 4059, Australia.,School of Optometry and Vision Science, Queensland University of Technology (QUT), Brisbane, QLD 4059, Australia
| | - Prakash Adhikari
- Centre for Vision and Eye Research, Queensland University of Technology (QUT), Brisbane, QLD 4059, Australia.,School of Optometry and Vision Science, Queensland University of Technology (QUT), Brisbane, QLD 4059, Australia
| | - Beatrix Feigl
- Centre for Vision and Eye Research, Queensland University of Technology (QUT), Brisbane, QLD 4059, Australia.,School of Biomedical Sciences, Queensland University of Technology (QUT), Brisbane, QLD 4059, Australia.,Queensland Eye Institute, Brisbane, QLD 4101, Australia
| | - Andrew J Zele
- Centre for Vision and Eye Research, Queensland University of Technology (QUT), Brisbane, QLD 4059, Australia.,School of Optometry and Vision Science, Queensland University of Technology (QUT), Brisbane, QLD 4059, Australia
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Barrionuevo PA, Paz Filgueira C, Cao D. Is melanopsin activation affecting large field color-matching functions? JOURNAL OF THE OPTICAL SOCIETY OF AMERICA. A, OPTICS, IMAGE SCIENCE, AND VISION 2022; 39:1104-1110. [PMID: 36215541 DOI: 10.1364/josaa.457223] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/28/2022] [Accepted: 05/11/2022] [Indexed: 06/16/2023]
Abstract
Color theory is based on the exclusive activation of cones. However, since the discovery of melanopsin expressing cells in the human retina, evidence of its intrusion in brightness and color vision is increasing. We aimed to assess if differences between peripheral or large field and foveal color matches can be accounted for by melanopsin activation or rod intrusion. Photopic color matches by young observers showed that differences between extrafoveal and foveal results cannot be explained by rod intrusion. Furthermore, statistical analyses on existing color-matching functions suggest a role of melanopsin activation, particularly, in large field S fundamentals.
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Gnyawali S, Feigl B, Adhikari P, Zele AJ. The role of melanopsin photoreception on visual attention linked pupil responses. Eur J Neurosci 2022; 55:1986-2002. [PMID: 35357050 PMCID: PMC9324975 DOI: 10.1111/ejn.15659] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2021] [Accepted: 03/22/2022] [Indexed: 12/01/2022]
Abstract
A decision during a visual task is marked by a task‐evoked pupil dilation (TEPD) that is linked to the global cortical arousal state. Melanopsin expressing intrinsically photosensitive retinal ganglion cells (ipRGCs) form the afferent pathway for this pupil response. Melanopsin activation also influences mood and arousal and increases activity in decision‐making brain areas that receive direct ipRGC projections. Here, an optical photostimulation method controlled the excitations of all five photoreceptor classes in the human eye to isolate melanopsin‐mediated photoreception. We hypothesised that the TEPD can be driven by directing active visual covert attention through the ipRGC pathway. When observers are completely certain of the stimulus presence, melanopsin‐directed stimulation produces a TEPD of similar amplitude to a cone‐directed stimulation, with their combination producing larger amplitudes. This dilation is satisfactorily modelled by linear addition with a higher melanopsin weighting in ipRGCs. Visual reaction times were longest in response to melanopsin‐directed lights. Next, we asked whether the afferent photoreceptor input and decision certainty, controlled by priming the observer's a priori expectation, interact to drive the TEPD. Signal detection analysis showed that by fixing the predecision certainty (bias), the phasic arousal and TEPD amplitude vary with observer criterion (c′) and sensitivity (d′) but not with preferential activation of melanopsin. The signature feature of the melanopsin response during attention was a biphasic TEPD. We conclude that active covert attention can be modulated by visual information mediated via ipRGCs, but that phasic arousal responses marked using the TEPD are not increased by higher levels of melanopsin activation.
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Affiliation(s)
- Subodh Gnyawali
- Melanopsin Photoreception and Visual Science Laboratories, Centre for Vision and Eye Research, Queensland University of Technology (QUT), Brisbane, QLD, Australia.,School of Biomedical Sciences, Queensland University of Technology (QUT), Brisbane, Australia
| | - Beatrix Feigl
- Melanopsin Photoreception and Visual Science Laboratories, Centre for Vision and Eye Research, Queensland University of Technology (QUT), Brisbane, QLD, Australia.,School of Biomedical Sciences, Queensland University of Technology (QUT), Brisbane, Australia.,Queensland Eye Institute, Brisbane, QLD, Australia
| | - Prakash Adhikari
- Melanopsin Photoreception and Visual Science Laboratories, Centre for Vision and Eye Research, Queensland University of Technology (QUT), Brisbane, QLD, Australia.,School of Optometry and Vision Science, Queensland University of Technology (QUT), Brisbane, QLD, Australia
| | - Andrew J Zele
- Melanopsin Photoreception and Visual Science Laboratories, Centre for Vision and Eye Research, Queensland University of Technology (QUT), Brisbane, QLD, Australia.,School of Optometry and Vision Science, Queensland University of Technology (QUT), Brisbane, QLD, Australia
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Seeing and sensing temporal variations in natural daylight. PROGRESS IN BRAIN RESEARCH 2022; 273:275-301. [DOI: 10.1016/bs.pbr.2022.04.013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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Pant M, Zele AJ, Feigl B, Adhikari P. Light adaptation characteristics of melanopsin. Vision Res 2021; 188:126-138. [PMID: 34315092 DOI: 10.1016/j.visres.2021.07.005] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2020] [Revised: 06/14/2021] [Accepted: 07/07/2021] [Indexed: 11/20/2022]
Abstract
Following photopigment bleaching, the rhodopsin and cone-opsins show a characteristic exponential regeneration in the dark with a photocycle dependent on the retinal pigment epithelium. Melanopsin pigment regeneration in animal models requires different pathways to rods and cones. To quantify melanopsin-mediated light adaptation in humans, we first estimated its photopigment regeneration kinetics through the photo-bleach recovery of the intrinsic melanopsin pupil light response (PLR). An intense broadband light (~120,000 Td) bleached 43% of melanopsin compared to 86% of the cone-opsins. Recovery from a 43% bleach was 3.4X slower for the melanopsin than cone-opsin. Post-bleach melanopsin regeneration followed an exponential growth with a 2.5 min time-constant (τ) that required 11.2 min for complete recovery; the half-bleaching level (Ip) was ~ 4.47 log melanopic Td (16.10 log melanopsin effective photons.cm-2.s-1; 8.25 log photoisomerisations.photoreceptor-1.s-1). The effect on the cone-directed PLR of the level of the melanopsin excitation during continuous light adaptation was then determined. We observed that cone-directed pupil constriction amplitudes increased by ~ 10% when adapting lights had a higher melanopic excitation but the same mean photometric luminance. Our findings suggest that melanopsin light adaptation enhances cone signalling along the non-visual retina-brain axis. Parameters τ and Ip will allow estimation of the level of melanopsin bleaching in any light units; the data have implications for quantifying the relative contributions of putative melanopsin pathways to regulate the post-bleach photopigment regeneration and adaptation.
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Affiliation(s)
- Mukund Pant
- Centre for Vision and Eye Research, Queensland University of Technology (QUT), Brisbane, QLD 4059, Australia; School of Optometry and Vision Science, Queensland University of Technology (QUT), Brisbane, QLD 4059, Australia
| | - Andrew J Zele
- Centre for Vision and Eye Research, Queensland University of Technology (QUT), Brisbane, QLD 4059, Australia; School of Optometry and Vision Science, Queensland University of Technology (QUT), Brisbane, QLD 4059, Australia
| | - Beatrix Feigl
- Centre for Vision and Eye Research, Queensland University of Technology (QUT), Brisbane, QLD 4059, Australia; School of Biomedical Sciences, Queensland University of Technology (QUT), Brisbane, QLD 4059, Australia; Queensland Eye Institute, Brisbane, Australia
| | - Prakash Adhikari
- Centre for Vision and Eye Research, Queensland University of Technology (QUT), Brisbane, QLD 4059, Australia; School of Optometry and Vision Science, Queensland University of Technology (QUT), Brisbane, QLD 4059, Australia.
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