title: The role of electrophonics in electroacoustic stimulation of the guinea pig cochlea.
abstract: OBJECTIVE
  Interactions between cochlear responses to combined electrical and acoustic stimulation (EAS) depend on electrically evoked hair cell activity (i.e., electrophonics).
  
  
  BACKGROUND
  Although relevant for EAS strategies in cochlear implant users with residual low-frequency hearing, cochlear responses to EAS are not well characterized. Previously, we have shown that acoustically evoked compound action potentials (CAPs) can be suppressed by electrical stimulation. In the present study, we characterized the role of electrophonics in CAP suppression in guinea pigs, under conditions representative of clinically applied EAS.
  
  
  METHODS
  Electrophonics depend on the frequency spectrum of the electric pulse train, which is mainly determined by pulse width and, to a lesser extent, by pulse rate. We measured suppression of tone-evoked CAPs by electric pulse trains, while varying the pulse width (80 - 400 μs, n = 5) and the pulse rate (500 - 4000 pps, n = 5). The role of outer hair cells (OHCs) in electrophonics was tested in animals with varying degrees of OHC loss (n = 24).
  
  
  RESULTS
  Suppression of acoustically evoked CAPs varied with pulse width, indicating that electrophonics were involved. Short pulse widths resulted in minimal CAP suppression at low acoustic frequencies. Pulse rate did not significantly affect CAP suppression. OHC loss had no significant effect on electrophonic activity.
  
  
  CONCLUSIONS
  Electrophonic activity was present in cochleae with extensive basal hair cell loss, indicating that electrophonics can occur in EAS users. Our results show that short pulse widths are optimal for use in EAS stimulation strategies, on the assumption that minimal suppression is best.
authors: Department of Otorhinolaryngology and Head and Neck Surgery, Rudolf Magnus Institute of Neuroscience, University Medical Center Utrecht, Utrecht, The Netherlands. Christiaan.Stronks@nicta.com.au
authors: H Christiaan
authors: HC
authors: Stronks
authors: Huib
authors: H
authors: Versnel
authors: Vera F
authors: VF
authors: Prijs
authors: John C M J
authors: JC
authors: de Groot
authors: Wilko
authors: W
authors: Grolman
authors: Sjaak F L
authors: SF
authors: Klis
mesh_terms: D000161:Acoustic Stimulation; D000818:Animals; D003051:Cochlea / Q000502:physiology*; D004558:Electric Stimulation; D005072:Evoked Potentials, Auditory / Q000502:physiology*; D005260:Female; D006168:Guinea Pigs; D006199:Hair Cells, Auditory, Inner / Q000502:physiology*