title: Estimation of psychophysical levels using the electrically evoked compound action potential measured with the neural response telemetry capabilities of Cochlear Corporation's CI24M device.
abstract: OBJECTIVE
  The goal of this study was to estimate psychophysical levels using the electrically evoked compound action potential (EAP), measured with the Neural Response Telemetry capabilities of Cochlear Corporation's Nucleus CI24M cochlear implant system.
  
  
  METHODS
  Twelve postlingually deafened adults with at least 3 mo of implant experience with the CI24M were subjects in this study. EAP growth functions were successfully quantified on each active electrode of every subject. Correlation and regression analyses were performed between EAP measures and cochlear implant fitting psychophysics. Other information including performance, etiology and duration of hearing loss, and individual electrode impedance was considered.
  
  
  RESULTS
  EAP thresholds were found to be highly correlated with psychophysical thresholds. The rate of EAP growth with increasing stimulation levels was also found to be correlated with the dynamic range of loudness limits and psychophysical thresholds in some subjects. No relationship was evident between EAP measures and speech perception tests.
  
  
  CONCLUSIONS
  Information from EAP growth function measurements may be used to estimate psychophysical information used in cochlear implant fitting but not to predict performance with the device.
authors.affiliation: Department of Speech and Hearing Sciences, University of Washington, Seattle, USA.
authors.forename: K H
authors.initials: KH
authors.lastname: Franck
authors.forename: S J
authors.initials: SJ
authors.lastname: Norton
mesh_terms: D000328:Adult; D001309:Auditory Threshold / Q000502:physiology*; D003054:Cochlear Implants; D003638:Deafness / Q000601:surgery; D004558:Electric Stimulation / Q000295:instrumentation; D004867:Equipment Design; D005071:Evoked Potentials / Q000502:physiology*; D006801:Humans; D008144:Loudness Perception / Q000502:physiology; D008875:Middle Aged; D017755:Prosthesis Fitting; D011601:Psychophysics / Q000295:instrumentation / Q000379:methods; D013686:Telemetry / Q000295:instrumentation