Project C1 – Direct approach to study temporal processing in the auditory system: electrical stimulation of the auditory nerve in cochlear implant patients

The auditory system is an excellent model to study temporal aspects of neural processing because precise temporal cues provide the essential information for sound localization and the segregation of competing sound sources. Recently, we have developed a detailed model of the human inner ear, which codes sound signals into trains of action potentials [1]. We used this model to excite simulated auditory-brainstem neurons [2] and characterized their information processing capabilities using the framework of information theory [3] and automatic speech recognition [4].

Objectives and description of the project

We will exploit a novel approach to investigate temporal information processing by conducting measurements in cochlear implant patients with MED-EL’s Research Interface Box, which allows us to access the auditory nerve directly, bypassing the mechanical pre-processing of the cochlea. Our focus will be o n precise interaural time differences, which provide cues for spatial sound localization. In patients with bilateral implants, we will investigate the limits of interaural time-difference resolution. In collaboration with the future Professor for Audio-Signal Processing we will design experiments and models to elucidate how temporal information processing degrades with hearing loss and age, comparing normal hearing subjects and subjects with conventional hearing aids. A second focus will be on the interaction of pulse-pairs in the time domain. We will use this approach to dissect the linear and nonlinear functions that lead to auditory nerve stimulation. The data will allow us to develop and evaluate models of the electrical stimulation of the auditory nerve. We expect that our approach will shed new light on the degradation of the hearing system and also lead to novel rehabilitation strategies.

[1]: Holmberg and Hemmert J Acoust Soc Am submitted, 2009. [2]: Wiegrebe and Meddis J Acoust Soc Am 2004. [3]: Wang et al. IEEE ICASSP 2006. [4]: Holmberg et al. Speech Com 2007.