The Effect of Varying the Inter-stimulus Interval on Auditory Stream Segregation in Individuals with Normal Hearing and Cochlear Hearing Loss

Abstract

Background: The present study investigates the impact of cochlear damage on auditory fusion and fission thresholds, particularly focusing on changes in the Inter-Stimulus Interval (ISI) of input signals in auditory stream segregation. The research employs the ABA with F0 discrimination paradigm to measure these thresholds in both normal-hearing and pathological cochlea-affected adults. Fusion and fission thresholds play a crucial role in integrating or segregating sounds, enhancing communication in challenging listening conditions, particularly concerning individuals with hearing loss. While previous studies have explored the effects of cochlear damage on spectral aspects, this research delves into temporal processing, filling a gap in our understanding of auditory processing abilities in pathological groups. Method: Thirty adults subjects, divided into two groups, participated in the study. Group I consisted of individuals with normal hearing and Group II with cochlear hearing loss. ABA with F0 discrimination paradigm assessed fission and fusion thresholds. The F0 between A and B was varied in semitones. In fission, the subjects listened to the sequence of sounds occurring rapidly, and perceived them as hearing more than one stream. If they perceived it as a single stream, it led to fusion percept. The responses were recorded for ten ISIs (from 10 to 100 ms in 10 ms steps). Results: The fusion and fission thresholds obtained for individuals with normal hearing and those with hearing loss were compared within groups across ISIs and between the groups. The fusion and fission thresholds showed a significant within group effect, i.e., a significant effect of ISI on thresholds. There was also a significant effect of hearing loss across all ISI. Normal hearing individuals had better thresholds than individuals with hearing loss across all ISIs. The results showed that both hearing loss and ISI affect auditory stream segregation, indicating that along with the frequency, the temporal aspects are also affected in individuals with mild-moderate cochlear hearing loss. Conclusion: The findings of this study show that individuals with hearing impairment have difficulties often with temporal processing along with impaired spectral resolution.