Light adaptation in cone vision involves switching between receptor and post-receptor sites

• Published in: Nature 2007-10, Vol.449 (7162), p.603-606
• Main Authors: DUNN, Felice A, LANKHEET, Martin J, RIEKE, Fred
• Format: Article
• Language: English
• Subjects: Adaptation; Adaptation (Physiology); Adaptation, Ocular - physiology; Adaptation, Ocular - radiation effects; Animals; Biological and medical sciences; Cones (Photoreceptors); Eye and associated structures. Visual pathways and centers. Vision; Fundamental and applied biological sciences. Psychology; Humans; Light; Macaca fascicularis; Macaca nemestrina; Models, Animal; Neurobiology; Neurosciences; Papio anubis; Photoreception; Photoreceptors; Retinal Bipolar Cells - metabolism; Retinal Bipolar Cells - radiation effects; Retinal Cone Photoreceptor Cells - metabolism; Retinal Cone Photoreceptor Cells - radiation effects; Retinal Ganglion Cells - metabolism; Retinal Ganglion Cells - radiation effects; Vertebrates: nervous system and sense organs; Vision; Vision, Ocular - physiology; Vision, Ocular - radiation effects
• ISSN: 0028-0836; 1476-4687; 1476-4679
• DOI: 10.1038/nature06150

We see over an enormous range of mean light levels, greater than the range of output signals retinal neurons can produce. Even highlights and shadows within a single visual scene can differ approximately 10,000-fold in intensity-exceeding the range of distinct neural signals by a factor of approximately 100. The effectiveness of daylight vision under these conditions relies on at least two retinal mechanisms that adjust sensitivity in the approximately 200 ms intervals between saccades. One mechanism is in the cone photoreceptors (receptor adaptation) and the other is at a previously unknown location within the retinal circuitry that benefits from convergence of signals from multiple cones (post-receptor adaptation). Here we find that post-receptor adaptation occurs as signals are relayed from cone bipolar cells to ganglion cells. Furthermore, we find that the two adaptive mechanisms are essentially mutually exclusive: as light levels increase the main site of adaptation switches from the circuitry to the cones. These findings help explain how human cone vision encodes everyday scenes, and, more generally, how sensory systems handle the challenges posed by a diverse physical environment.