Objective Measure Of Auditory Stream Segregation With Cochlear Implants Using Mismatch Negativity

For patients with profound-to-severe hearing loss,cochlear implant(CI)can be used to partially restore their hearing.While most CI users are able to perceive sound and understand speech in a quiet environment,there are still many challenges for them in noise.In a real listening environment,listeners need to parse all the sounds firstly,group the sounds into different auditory streams,and then selectively focus on the sound stream of interest.Therefore,the separation ability of the auditory stream plays a crucial role in the listener's listening experience in a complex environment.Compared with normal hearing listeners,many early works had showed that CI patient had defects in the ability of auditory stream segregation.If the auditory stream segregation performance of the CI users could be objectively evaluated and key factors affecting the segregation performance could be identified,future work could improve the listening experience of CI users and help them gain better speech perception in complex environments.Previous experiments commonly used behavioral measurement methods to evaluate CI users' auditory stream segregation.As a physical test method,behavioral experiment has a number of uncertain factors due to subjective judgment and requires a high degree of cooperation of the subjects.It often affects the accuracy of experimental results and is not suitable for clinical applications.Therefore,in this study,MMN(mismatch negativity),one of the components of brain wave,was used as an objective evaluation index to evaluate the auditory stream segregation in CI population.In the experiment,a vocoder model was used to simulate CI speech processing and CI users' speech perception,and the frequency separation and time interval between the two auditory streams were separately explored.Experimental results showed that the frequency separation and time interval notably affected the auditory stream segregation performance under CI conditions.The larger the frequency separation or the smaller the time interval,the better the auditory stream segregation performance.In addition,experimental results also showed that MMN could be used as an objective physiological indicator to assess the auditory stream segregation performance of CI users.The results of this study laid a valuable foundation for the future study of the auditory stream segregation performance of CI users,and the research findings may provide some guidance for the future design of CI devices and the auditory rehabilitation strategy for implanted users.