Auditory after-effects revealing adaptive representation of auditory space

Abstract

After-effects refer to distortions of perception following prolonged exposure to a stimulus. In vision, various after-effects have been known for years and have proven to be useful tools in analyzing processing channels of the perceptual system. On the other hand, few after-effects have been reported in hearing. The authors have been studying auditory after-effects affecting sound localization in order to investigate dynamic aspects of auditory spatial representation. It was found that exposure to a sound alters the perceived localization of a subsequent sound, depending on the frequency relationship and interaural time difference (ITD) relationship between the two sounds. It was also found that adaptation to a sound affects the discrimination of ITDs of the following sounds: ITD discrimination is selectively improved in the neighborhood of the preceding sound, and reduced elsewhere. Together, these results indicate that the internal representation of auditory space is not fixed, but adaptive. The responsible mechansims are recalibrated during stimulation so that they can represent recently experienced sounds with the maximum resolution. Such adaptive representations of auditory space provide a basis for efficient information processing of auditory events in the ever-changing real-world environment.