Temporal Coding for Hearing Implants Optimized with EASSR

Objective: Temporal information transfer is limited in auditory prostheses because of the rather artificial stimulation of the neuronal networks with electrical biphasic pulses. According to the patents filed in 2014 (Bahmer: Temporal coding for hearing implants (WO2014070553A1, 2014) - Bahmer: Auditory prosthesis using stimulation rate as a multiple of periodicity of sensed sound (WO2015026688A1, 2014) – Bahmer/Schleich: Auditory Prosthesis Stimulation Rate as a Multiple of Intrinsic Oscillation (US9398382, 2014)) we propose a closed loop system that assesses the neuronal representation of a stimulation modulation and optimizes iteratively the stimulation mode (multi-channel) by genetic algorithms. Neurophysiologic measurement for closed loop may include electrically evoked auditory steady state responses (EASSR), electrically evoked brainstem response audiometry (EBERA), near field measurements, and/or electrically evoked compound action potentials (ECAP)

Methods: Multi-Channel ECAP, EABR, and EASSR was assessed in ABI and CI (MEDEL).

Results: EABR latency show intrinsic constant 0.4ms which corroborates our idea of a stimulation rate as a multiple of intrinsic oscillation. Multi-channel ECAP shows clear auditory nerve responses. EASSR responses show the feasibility of recording EASSR using the Hofmann method and jittered stimuli with MEDEL implants.

Conclusion: The prerequisite for a closed loop system were successfully tested. Multi-channel electrode array having electrodes that are spatially divided will be tested for EASSR.