Electrophysiological Characterization of Auditory Neuron Response Profiles on Multi-Electrode Arrays

Objective. Cochlear implants (CI) are a very successful type of neuroprosthetic device, which are globally used as gold standard treatment for deafness. Despite the many advances made in the development of cochlear implants, some limitations still remain, such as poor frequency resolution and high-energy consumption. It is thought that the anatomical gap between the implanted electrode array and the spiral ganglion neurons (SGNs) might be one of the limiting factors. Therefore we analyzed the electrophysiological features of SGNs growing in close contact with an electrode array. Approach. We characterized SGN responses to extracellular stimulation in vitro using multi-electrode arrays (MEAs). SGN explants were obtained either from the cochlear’s apex or the base and were cultured with two different neurotrophic factors – brain-derived neurotrophic factor (BDNF) and/or neurotrophin-3 (NT- 3) – that are known to have opposing influences on apex and base. Main results. SGN explant culturing was successful in all six conditions: independently from the anatomical location or the supplemented neurotrophins, spontaneous and stimulated neuronal activity could be recorded in all six conditions. A difference in neuronal threshold values as well as in their accommodation was observed between apex and base depending on the supplemented neurotrophins. Significance. Understanding the relation of neurotrophic factors to apical and basal SGNs could help to improve the contact of SGNs with the electrode array as well as to include location-specific firing features of cochlear SGNs in the stimulation patterns