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Updated: Oct 7, 2026

Inducing Daytime Circadian Phase Shifts Using Chemogenetic and Spectral Approaches
Published on: June 12, 2026
Extraocular phototransduction and circadian timing systems in vertebrates
S S Campbell1, P J Murphy, A G Suhner
1Department of Psychiatry, Weill Medical College of Cornell University, White Plains, New York, USA. sscampb@med.cornell.edu
Abstract:
It is widely accepted that, for organisms with eyes, the daily regulation of circadian rhythms is made possible by light transduction through those organs. Yet, it has been demonstrated repeatedly in recent years that ocular light receptors that mediate vision, at least in mammals, are not the same photoreceptors involved in circadian regulation. Moreover, it has been recognized for many years that circadian regulation can occur in organisms without eyes. In fact, extraocular circadian phototransduction (EOCP) appears to be a phylogenetic rule for the vast majority of species. EOCP has been reported in every nonmammalian species studied to date. In mammals, however, the story is very different. This paper presents findings from studies that have examined specifically the capacity for EOCP in vertebrate species. In addition, the literature addressing noncircadian aspects of extraocular phototransduction is briefly discussed. Finally, possible mechanisms underlying EOCP are discussed, as are some of the implications of the presence, or absence, of EOCP across phylogeny.
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