ELECTROPHYSIOLOGIC CORRELATES OF SPATIAL RELEASE FROM MASKING

Abstract

Speech is difficult to understand in the presence of background noise. When the speech signal and source(s) of the background noise are spatially separated, it becomes easier to detect the speech. This is known as spatial release from masking (SRM). Previous research using perceptual test methods has demonstrated that listeners with hearing loss have variable benefit from SRM. This study documented the benefits of SRM using the cortical auditory evoked potential (CAEP) in response to speech tokens as noise level and location were varied. CAEPs from twenty normally hearing adults were recorded in response to consonant-vowel speech tokens in quiet, co-located noise and spatially separated noise. SRM benefit was measured by comparing the latency an amplitude of CAEP components P1, N1, and P2 in co-located and spatially separated conditions. Psychophysical tests of speech perception were completed in the same co-located and spatially separated noise conditions. Latencies and amplitudes of the CAEP components showed a systematic shift as a function of noise location, level, SNR, and stimulus. Co-located conditions across all stimuli, levels, and SNRs had longer latencies and smaller amplitudes than the spatially separated conditions, demonstrating an electrophysiologic analog of perceptual SRM. These results provide a baseline for investigation of SRM benefits in adults with hearing loss.