Multichannel cochlear implant for selective neuronal activation and chronic use in the free-moving Mongolian gerbil

- First study to describe a multichannel CI for chronic use in the Mongolian gerbil.
- Selective and tonotopic neuronal activation was evident in auditory cortex.
- Impedances and EABR thresholds were stable over weeks after implantation.
- Chronic electrical stimulation was safe and effective in the free-moving gerbil.

BackgroundAnimal models for chronic multichannel cochlear implant stimulation and selective neuronal activation contribute to a better understanding of auditory signal processing and central neural plasticity.New methodThis paper describes the design and surgical implantation of a multichannel cochlear implant (CI) system for chronic use in the free-moving gerbil. For chronic stimulation, adult-deafened gerbils were connected to a multichannel commutator that allowed low resistance cable rotation and stable electric connectivity to the current source.ResultsDespite the small scale of the gerbil cochlea and auditory brain regions, final electrophysiological mapping experiments revealed selective and tonotopically organized neuronal activation in the auditory cortex. Contact impedances and electrically evoked auditory brainstem responses were stable over several weeks demonstrating the long-term integrity of the implant and the efficacy of the stimulation.Comparison with existing methodsMost animal models on multichannel signal processing and stimulation-induced plasticity are limited to larger animals such as ferrets, cats and primates. Multichannel CI stimulation in the free-moving rodent and evidence for selective neuronal activation in gerbil auditory cortex have not been previously reported.ConclusionsOverall, our results show that the gerbil is a robust rodent model for selective and tonotopically organized multichannel CI stimulation. We anticipate that this model provides a useful tool to develop and test both passive stimulation and behavioral training strategies for plastic reorganization and restoration of degraded unilateral and bilateral central auditory signal processing in the hearing impaired and deaf central auditory system.