Neurophysiological Mechanisms of Intensity Discrimination in the Goldfish

The detection of changes in sound intensity (ΔI) is one of the fundamental auditory capacities for which auditory systems have presumably been “designed” throughout evolution. Questions of the neural representations of sound intensity, and the ways these are processed by the brain are basic to an analysis of sensory coding. The psychophysical literature contains two major observations: (1) The ratio ΔI/I is approximately constant for noise signals within a wide range of I values (i.e., Weber’s law holds) (Miller 1947, Rodenburg 1972). (2) For tone signals, ΔI/I declines somewhat at larger I values (i.e., there is a “near miss” to Weber’s law) (Reisz 1928, McGill and Goldberg 1968, Jesteadt, Wier, and Green 1977, Steigel 1977).