Neural Adaptation and Temporal Integration

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Currently, cochlear implant devices are designed to stimulate auditory nerve fibers at rapid rates of presentation (...i e ,>1000 pulses/second). With. increased stimulation rates, the auditory., nerve shows the effects of adaptation. The amount of adaptation has been shown to vary across ind_wduals and across electrodes within an individual. This adapted neural response will be related to the input to the central integrator, or central auditory system, and it is possible that the time course of adaptation could affect the degree of temporal integration. The objective of this study, therefore, is to identify the relationship between peripheral neural adaptation and behavioral temporal integration in cochlear implant recipients. It is anticipated that information from this study will have direct application for the setting of individual cochlear implant devices. Neural adaptation will be measured by tracking amplitude changes of the electrically evoked compound action potential (ECAP) to varying lengths of rapid rate biphasic pulse trains. Temporal integration will be assessed through the use of a loudness balancing procedure and through the use of two threshold measures. Both electrophysical and psychophysical measures will be performed along the electrode array and across individual cochlear implant recipients. Correlation and linear regression analyses will be used to determine the relationship between neural adaptation and temporal integration.