Abstract
One of the fundamental tenets of sensory biology is that sensory systems adapt to environmental change. It has been argued that adaptation should have the effect of optimizing sensitivity to properties of the variable environment (Sakitt and Barlow, 1982; Wainwright, 1999; Stocker and Simoncelli, 2005). Previous efforts to support this premise in motion adaptation have produced controversial results (e.g., Clifford and Wenderoth, 1999; Krekelberg, van Wezel, and Albright, 2006). We have developed a normative-economic theory of motion adaptation which assumes that adaptation in the visual system amounts to finding a new balance of stimulus and measurement uncertainties as the stimulation changes. Stimulus uncertainty is determined by the statistics of stimulation whereas measurement uncertainty is determined by the uncertainty principle of measurement (Gabor, 1946; Gepshtein, Tyukin, and Kubovy, 2007). The theory is economic in the sense that it prescribes how system resources — motion sensitive cells — ought to be reallocated across the parameters of stimulation in face of variable environment. The theory predicts specific changes of the spatiotemporal sensitivity surface (Kelly, 1979) as a function of environmental statistics, such as to minimize errors in the estimation of speed, stimulus location, and stimulus frequency content. The adaptive optimization is manifested both as global changes in behavioral spatiotemporal sensitivity and as changes in tuning of the motion-sensitive neurons. The theory predicts a counterintuitive pattern of sensitivity change similar to the one that have puzzled researchers of motion adaptation. For example, sensitivity to the adapting speed either increases or decreases depending on the parameters of stimuli used to measure the effect of adaptation; sensitivity also changes for speeds very different from the adapting speed.
Supported by grants from the Japanese Institute of Natural Sciences (to S.G.), The Royal Society - the UK's National Academy of Science (to I.T.), and the National Eye Institute (to T.D.A.).