Optical Stimulation of the Auditory Nerve

Improvements in cochlear implant devices during the last decade have mainly been achieved through novel coding strategies rather than through improvement of the neural interface. The neural interface, however, is a bottleneck for transferring information from the cochlear implant to the auditory nerve. Electric current spreads in the tissue and neighboring electrode contacts cannot be considered independent stimulation sources. Simultaneous transfer of information at adjacent electrodes may lead to deleterious interactions. Therefore, contemporary coding strategies use sequential stimulation paradigms that avoid simultaneous stimulation at neighboring electrode contacts. These coding strategies provide good speech recognition in quiet listening environments but fail in noisy backgrounds. It has been argued that an increase in the number of independent channels that transfer information to the auditory nerve could improve patient performance in noisy listening environments. Therefore, an important objective in implant electrode design is to maximize the spatial selectivity of stimulation.