Distinct contributions of rod, cone, and melanopsin photoreceptors to encoding irradiance.
Bottom Line: These photoreceptors define circadian responses at very dim "scotopic" light levels but also at irradiances at which pattern vision relies heavily on cones.By contrast, cone input to irradiance responses dissipates following light adaptation to the extent that these receptors make a very limited contribution to circadian and pupillary light responses under these conditions.Our data provide new insight into retinal circuitry upstream of mRGCs and optimal stimuli for eliciting irradiance responses.
Affiliation: Faculty of Life Sciences, AV Hill Building, University of Manchester, Manchester M13 9PT, UK.Show MeSH
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Mentions: The red cone knockin allele (referred to here as Opn1mwR) results in a substantial, long-wavelength shift in the spectral sensitivity of those cones that would ordinarily express m-cone opsin (Figure 1; Smallwood et al., 2003). Electrophysiological and behavioral assessments suggest that these red cones retain normal function and retinal connectivity (Jacobs et al., 2007; Smallwood et al., 2003). To determine whether they are capable of driving NIF responses, we first compared pupillary responses to bright medium- (500 nm) and long-wavelength (650 nm) stimuli in Opn1mwR males with those of littermate wild-type mice. As expected, the two genotypes had equivalent responses to 500 nm (Figure 1C). However, 650 nm induced much larger constriction in Opn1mwR animals (Figure 1C), suggesting involvement of cones in this response.
Affiliation: Faculty of Life Sciences, AV Hill Building, University of Manchester, Manchester M13 9PT, UK.