Hearing restoration by a low-weight power-efficient multichannel optogenetic cochlear implant system.

Objective.In case of deafness, electrical cochlear implants (eCIs) bypass dysfunctional or lost hair cells by direct stimulation of the auditory nerve. However, spectral selectivity of eCI sound coding is low as the wide current spread from each electrode activates large sets of neurons along the tonotopic axis of the cochlea. As light can be better confined in space, optical cochlear implants (oCIs) combined with cochlear optogenetics promise to overcome this shortcoming of eCIs. This requires appropriate sound processing and control of multiple microscale emitters.Approach.Here, we describe the development, characterisation, and application of a preclinical miniaturised low-weight and wireless LED-based multichannel oCI system for hearing restoration, and its comparison to its sister eCI system. We present exemplary implementation of these systems in behavioural studies on freely moving rats.Main results.The system, which weights 15 g, is 20 mm in diameter and 20 mm in height, performed for up to 8 h in behavioural experiments on freely moving rats proving its utility for cueing auditory tasks in deaf animals.Significance.The head-worn oCI system enabled deafened rats to perform a locomotion task in response to acoustic stimulation proving the concept of multichannel optogenetic hearing restoration in rodents. This paves the way for implementation in other species and development of future clinical oCI systems for improved hearing restoration.