Psychophysical and physiological studies of the precedence effect and echo threshold in the behaving cat

Abstract

The precedence effect (PE) is an auditory spatial illusion where the apparent location of two sounds presented from different spatial locations but separated by a delay is determined primarily by the spatial attributes of the leading stimulus. In this review, we compare previously published psychophysical and physiological experiments on the PE in cats. Also included are data from some new psychophysical studies allowing further comparisons to published physiological results. Psychophysical experiments on the precedence effect (on the PE in cats) in cats have shown that they perceive pairs of auditory stimuli presented from different locations in space in a manner dependent on the interstimulus delay (ISD) between stimuli, similar to humans. The behavior of the cats indicates that they experience the phases of the PE, including summing localization, localization dominance, and the echo threshold. These three phenomena of the PE are elicited on the horizontal and vertical planes using ISDs. Here, we present new psychophysical data showing that the PE can also be elicited on the horizontal plane using interstimulus intensity differences (ISIs) and can be disrupted with conflicting ISDs and ISIs. While neural mechanisms of the PE phenomena are less known, single unit recordings from the inferior colliculus (IC) of anesthetized cats support the hypothesis that the IC is an important neural substrate of the PE.