Modeling Physiological and Psychophysical Responses to Precedence Effect Stimuli

Many perceptual and physiological studies of sound localization have explored the precedence effect (PE), whereby two dichotic clicks coming from different directions and arriving at the ears close together in time are perceived as one event coming from the location of the click arriving first. Here, we used a computational model of low-frequency inferior colliculus (IC) neurons to account for both physiological and psychophysical responses to PE stimuli. In the model, physiological suppression of the ITD-tuned lagging response depends on the inter-stimulus delay (ISD) between the leading and lagging sound as well as the ITD of the lead. Psychophysical predictions generated from a population of model IC neurons estimate the perceived location of the lagging click as near that of the lead click at short ISDs, consistent with subjects perceiving both lead and lag as coming from the lead location. As ISD increases, the estimated location of the lag becomes closer to the true lag location, consistent with listeners perceiving two sounds coming from separate locations. Together, these physiological and perceptual simulations suggest that ITD-dependent suppression in IC neurons can explain the behavioral phenomenon known as the PE.