LIGHT SENSITIVITY, ADAPTATION AND SATURATION IN MAMMALIAN RODS

This chapter discusses the absolute sensitivity, background desensitization, and saturation in guinea-pig rods. The principal purpose of this study is to establish the extent and the conditions for rod adaptation in mammals and compare them with those of lower vertebrates. In agreement with a recent report, it was found that guinea pig rods possess adaptation properties qualitatively similar to those of amphibian rods. It was also found that light-adapted guinea-pig rods may efficiently signal light changes up to background levels that for a human subject would be equivalent to ambient illuminations of over l03 candles (cd)/m2. Considering that a dark-adapted rod may generate a detectable response to the absorption of a few photons, the range of light intensity over which a single rod may efficiently contribute to vision covers more than 4 log units. © 1993, Academic Press Inc.