Back-Up Lighting Systems

Specific ganglion cells in the mammalian retina regulate responses to light without forming images, including entrainment of the circadian clock. However, genetic studies in mice have suggested that this response to light remains largely intact even in the absence of these photoreceptors. Panda et al. now report that the photoreceptors in mice of the classical image-forming visual system (rods and cones) also regulate light input into the photoresponse process that does not form images. This finding indicates that light inputs from multiple photoreceptor types are integrated in the control of processes such as circadian rhythm. S. Panda, I. Provencio, D. C. Tu, S. S. Pires, M. D. Rollag, A. M. Castrucci, M. T. Pletcher, T. K. Sato, T. Wiltshire, M. Andahazy, S. A. Kay, R. N. Van Gelder, J. B. Hogenesch, Melanopsin is required for non-image-forming photic responses in blind mice. Science 301, 525-527 (2003). [Abstract] [Full Text]