12th congress of the European Federation of Audiology Societies (EFAS 2015) edition:12 location:Istanbul (Turkey) date:27-30 May 2015
Normal hearing listeners integrate input from two ears (binaural hearing). This allows them to localize sounds and to understand speech, even under acoustically challenging conditions.
The goal of the present study is to determine an objective measure of binaural hearing. In a first phase, 14 young normal hearing participants listened passively to binaurally presented sinusoidal amplitude-modulated tones. This enabled us to investigate neural temporal coding by means of Auditory Steady-State Responses (ASSRs). Different modulation frequencies (20, 40 and 80 Hz) were used to assess the contribution of different neural generators. The stimuli were 4 seconds in duration, with opposite phase shifts of 90° in the two ears, recurring every 400 milliseconds. These IPD changes were expected to elicit a short distortion in the synchronization of the ASSRs, which was used as a measure of binaural functioning. Results showed stable ASSRs and significant change responses elicited by the phase shifts in all participants for the 40 Hz modulation frequency. However, significant change responses for 20 (more cortical) and 80 (brainstem) Hz were only observed in 11 out of 14 participants. Currently, another measure is being evaluated for those participants in which the first measure led to inconclusive results. These data will be presented at the conference. A robust and objective measure of binaural functioning would enable us to optimize hearing aid fitting or it could be used as a measure of central auditory processing.