Timescales of adaptation to context in horizontal sound localization

Abstract

Psychophysical experiments explored how the repeated presentation of a context, consisting of an adaptor and a target, induces plasticity in the localization of an identical target presented alone on interleaved trials. The plasticity, and its time course, was examined both in a classroom and in an anechoic chamber. Adaptors and targets were 2-ms noise clicks and listeners were tasked with localizing the targets while ignoring the adaptors (when present). The context had either a fixed temporal structure, consisting of a single-click adaptor and a target, or its structure varied from trial to trial, either containing a single-click or an 8-click adaptor. The adaptor was presented either from a frontal or a lateral location, fixed within a run. The presence of context caused responses to the isolated targets to be displaced up to 14° away from the adaptor location. This effect was stronger and slower if the context was variable, growing over the 5-minute duration of the runs. Additionally, the fixed-context buildup had a slower onset in the classroom. Overall, the results illustrate that sound localization is subject to slow adaptive processes that depend on the spatial and temporal structure of the context and on the level of reverberation in the environment.