The search for the site of visual adaptation.

It was almost exactly 25 years ago as a graduate student in Electrical Engineering that my own intellectual curosity about mechanisms of visual adaptation was kindled. Adaptation is one of the most profound and pervasive sensory phenomena. After steady exposure to a sensory stimulus,, sensitivity is almost always decreased. Odors become less noticeable, lights appear dimmer, tastes become less strong and so on. Consequently its study is both interesting and important. It would be nice to say that my own interest stems from recognizing this, but somehow it didn’t happen like that. In fact the influence of people rather than ideas was most important. The journal (and I) began vision research in the middle of what I think of as the Rushton era. William A. H. Rushton was a brilliant, dynamic individual who made monumental contributions and for a time gave direction to much of our thinking and research on visual adaptation. It was hearing a lecture by W.A.H.R. himself in the fall of 1960 that served to channel my own interests toward the study of the visual system. Christina Enroth-Cugell had invited Rushton to deliver a lecture to the Biomedical Engineering group at Northwestern University in Evanston. As I recollect it, the lecture was an animated and forceful discourse on visual adaptation, covering much the same material published later that academic year in a paper titled, “The Intensity Factor in Vision” (Rushton, 196la). What I recall most vividly was Rushton’s vigorous attack of the pigment depletion explanation for the changes in sensitivity which occur when the eye adapts to light or darkness. The focus of his assualt was Selig Hecht’s simple and elegant photochemical ideas (Hecht, 1924).