title: Reducing Current Spread by Use of a Novel Pulse Shape for Electrical Stimulation of the Auditory Nerve.
abstract: Improving the electrode-neuron interface to reduce current spread between individual electrodes has been identified as one of the main objectives in the search for future improvements in cochlear-implant performance. Here, we address this problem by presenting a novel stimulation strategy that takes account of the biophysical properties of the auditory neurons (spiral ganglion neurons, SGNs) stimulated in electrical hearing. This new strategy employs a ramped pulse shape, where the maximum amplitude is achieved through a linear slope in the injected current. We present the theoretical framework that supports this new strategy and that suggests it will improve the modulation of SGNs' activity by exploiting their sensitivity to the rising slope of current pulses. The theoretical consequence of this sensitivity to the slope is a reduction in the spread of excitation within the cochlea and, consequently, an increase in the neural dynamic range. To explore the impact of the novel stimulation method on neural activity, we performed in vitro recordings of SGNs in culture. We show that the stimulus efficacy required to evoke action potentials in SGNs falls as the stimulus slope decreases. This work lays the foundation for a novel, and more biomimetic, stimulation strategy with considerable potential for implementation in cochlear-implant technology.
authors.affiliation: Ear Institute, University College London, London, UK.
authors.forename: Jimena
authors.initials: J
authors.lastname: Ballestero
authors.affiliation: Ear Institute, University College London, London, UK.
authors.forename: Matthieu
authors.initials: M
authors.lastname: Recugnat
authors.affiliation: Oticon Medical, Vallauris, France.
authors.forename: Jonathan
authors.initials: J
authors.lastname: Laudanski
authors.affiliation: Ear Institute, University College London, London, UK.
authors.forename: Katie E
authors.initials: KE
authors.lastname: Smith
authors.affiliation: Ear Institute, University College London, London, UK.
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Jagger
authors.affiliation: Oticon Medical, Vallauris, France.
authors.forename: Daniel
authors.initials: D
authors.lastname: Gnansia
authors.affiliation: Ear Institute, University College London, London, UK david.mcalpine@mq.edu.au.
authors.forename: David
authors.initials: D
authors.lastname: McAlpine
mesh_terms: D000161:Acoustic Stimulation / Q000379:methods; D000200:Action Potentials; D000818:Animals; D002478:Cells, Cultured; D003054:Cochlear Implants; D003056:Cochlear Nerve / Q000166:cytology / Q000378:metabolism*; D004558:Electric Stimulation / Q000379:methods*; D004594:Electrophysiology; D051379:Mice; D008810:Mice, Inbred C57BL; D023421:Models, Animal; D015221:Potassium Channels / Q000378:metabolism*; D012680:Sensitivity and Specificity; D012815:Signal Processing, Computer-Assisted; D013136:Spiral Ganglion / Q000166:cytology / Q000378:metabolism*; D006113:United Kingdom; D000159:Vestibulocochlear Nerve / Q000166:cytology / Q000502:physiology
chemical_list: D015221:Potassium Channels
keywords: auditory nerve; cochlear implant; electric stimulation; potassium channels; spiral ganglion neurons