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Melanopsin Contributions to Irradiance Coding in the Thalamo-Cortical Visual System

Brown, TM; Gias, C; Hatori, M; Keding, SR; Semo, M; Coffey, PJ; Gigg, J; ... Lucas, RJ; + view all (2010) Melanopsin Contributions to Irradiance Coding in the Thalamo-Cortical Visual System. PLOS BIOL , 8 (12) , Article e1000558. 10.1371/journal.pbio.1000558. Green open access

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Abstract

Photoreception in the mammalian retina is not restricted to rods and cones but extends to a subset of retinal ganglion cells expressing the photopigment melanopsin (mRGCs). These mRGCs are known to drive such reflex light responses as circadian photoentrainment and pupillomotor movements. By contrast, until now there has been no direct assessment of their contribution to conventional visual pathways. Here, we address this deficit. Using new reporter lines, we show that mRGC projections are much more extensive than previously thought and extend across the dorsal lateral geniculate nucleus (dLGN), origin of thalamo-cortical projection neurons. We continue to show that this input supports extensive physiological light responses in the dLGN and visual cortex in mice lacking rods+cones (a model of advanced retinal degeneration). Moreover, using chromatic stimuli to isolate melanopsin-derived responses in mice with an intact visual system, we reveal strong melanopsin input to the similar to 40% of neurons in the LGN that show sustained activation to a light step. We demonstrate that this melanopsin input supports irradiance-dependent increases in the firing rate of these neurons. The implication that melanopsin is required to accurately encode stimulus irradiance is confirmed using melanopsin knockout mice. Our data establish melanopsin-based photoreception as a significant source of sensory input to the thalamo-cortical visual system, providing unique irradiance information and allowing visual responses to be retained even in the absence of rods+cones. These findings identify mRGCs as a potential origin for aspects of visual perception and indicate that they may support vision in people suffering retinal degeneration.

Type: Article
Title: Melanopsin Contributions to Irradiance Coding in the Thalamo-Cortical Visual System
Open access status: An open access version is available from UCL Discovery
DOI: 10.1371/journal.pbio.1000558
Publisher version: http://dx.doi.org/10.1371/journal.pbio.1000558
Language: English
Additional information: © 2010 Brown et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: This work was funded by grants from the Wellcome Trust (RJL and HDP), National Institutes of Health grant EY016807, Dana Foundation grant and Pew Scholar award to SP, JSPS Fellowship to MH, and was supported in part by the London Project to Cure Blindness. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Keywords: RETINAL GANGLION-CELLS, LATERAL GENICULATE-NUCLEUS, RECEPTIVE-FIELD PROPERTIES, CONE PHOTORECEPTORS, CIRCADIAN CLOCK, MOUSE RETINA, OCULAR PHOTORECEPTORS, RESPONSE PROPERTIES, PHOTIC RESPONSES, DOUBLE REPORTER
UCL classification: UCL
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Brain Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Brain Sciences > Institute of Ophthalmology
URI: https://discovery.ucl.ac.uk/id/eprint/705655
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