Sarah Buchholz: Spatial hearing with bionic ears: What are the challenges for the auditory system?

Abstract 

 
 The healthy mammalian auditory system uses two different binaural cues to localize sound sources in the horizontal plane: interaural level differences and interaural time differences (ITDs). But how good is directional hearing with bionic ears? Already one million deaf patients have been able to learn to hear using the most successful brain-machine interface of our age, the cochlear implant (CI). However, spatial hearing is still one of the major challenges for these patients, especially if they suffer from early hearing loss. This is mainly due to poor sensitivity to ITDs, which also affects their speech understanding. Possible causes could be a lack of hearing experience during early development as well as technical limitations of the currently available processor technology. In fact, until today, no temporal synchronization of bilateral CI processors has been realized and therefore the presentation of spatial cues in these patients is very limited.

 We propose that even the deaf brain can develop good spatial hearing if it receives an optimized presentation of acoustic information via the bilateral CIs. To investigate this hypothesis we have performed unique behavioral studies in early deafened rats with bilateral CIs. In doing so, we have full control over all stimulation parameters, allowing us to address the question of how ‘asynchronized’ CIs (clinical standard) compared to ‘synchronized’ CIs (optimized stimulation strategy) affect spatial hearing. Our preliminary results showed improved spatial hearing performance with the use of synchronized CIs and suggest that current stimulation strategies need to be revised to provide CI patients with optimal auditory perception. 

About the speaker and her research

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