title: Characterization of pulse amplitude and pulse rate modulation for a human vestibular implant during acute electrical stimulation.
abstract: The vestibular system provides essential information about balance and spatial orientation via the brain to other sensory and motor systems. Bilateral vestibular loss significantly reduces quality of life, but vestibular implants (VIs) have demonstrated potential to restore lost function. However, optimal electrical stimulation strategies have not yet been identified in patients. In this study, we compared the two most common strategies, pulse amplitude modulation (PAM) and pulse rate modulation (PRM), in patients.
  
  
  
  Four subjects with a modified cochlear implant including electrodes targeting the peripheral vestibular nerve branches were tested. Charge-equivalent PAM and PRM were applied after adaptation to baseline stimulation. Vestibulo-ocular reflex eye movement responses were recorded to evaluate stimulation efficacy during acute clinical testing sessions.
  
  
  
  PAM evoked larger amplitude eye movement responses than PRM. Eye movement response axes for lateral canal stimulation were marginally better aligned with PRM than with PAM. A neural network model was developed for the tested stimulation strategies to provide insights on possible neural mechanisms. This model suggested that PAM would consistently cause a larger ensemble firing rate of neurons and thus larger responses than PRM.
  
  
  
  Due to the larger magnitude of eye movement responses, our findings strongly suggest PAM as the preferred strategy for initial VI modulation.
authors.affiliation: Bertarelli Foundation Chair in Translational Neuroengineering, School of Engineering, Center for Neuroprosthetics, Station 17, EPF Lausanne, 1015 Lausanne, Switzerland.
authors.forename: T A K
authors.initials: TA
authors.lastname: Nguyen
authors.forename: J
authors.initials: J
authors.lastname: DiGiovanna
authors.forename: S
authors.initials: S
authors.lastname: Cavuscens
authors.forename: M
authors.initials: M
authors.lastname: Ranieri
authors.forename: N
authors.initials: N
authors.lastname: Guinand
authors.forename: R
authors.initials: R
authors.lastname: van de Berg
authors.forename: J
authors.initials: J
authors.lastname: Carpaneto
authors.forename: H
authors.initials: H
authors.lastname: Kingma
authors.forename: J-P
authors.initials: JP
authors.lastname: Guyot
authors.forename: S
authors.initials: S
authors.lastname: Micera
authors.forename: A Perez
authors.initials: AP
authors.lastname: Fornos
mesh_terms: D000368:Aged; D003054:Cochlear Implants; D004424:Ear Canal / Q000502:physiology; D004558:Electric Stimulation; D005133:Eye Movements / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D008959:Models, Neurological; D016571:Neural Networks, Computer; D058117:Neural Prostheses; D009474:Neurons / Q000502:physiology; D011788:Quality of Life; D012027:Reflex, Vestibulo-Ocular / Q000502:physiology; D014726:Vestibular Nuclei / Q000502:physiology; D014722:Vestibule, Labyrinth