Characterization and Modelling of the Electrode-Nerve Interface for Electro-Acoustic Stimulation in Cochlear Implant Users

• Applicant: Professor Dr.-Ing. Waldo Nogueira
• Subject Area: Medical Physics, Biomedical Technology ; Otolaryngology, Phoniatrics and Audiology
• Term: from 2018 to 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 396932747

• Final Report Year: 2022

Final Report Abstract

In this project we discovered different forms of interaction in cochlear implant (CI) users with residual hearing in the same ear presenting electric and acoustic stimuli through psychoacoustic masking experiments. These preliminary results demonstrated electric acoustic interaction, and most surprising showed that an acoustic stimulus reduced the perception of an electric stimulus. An asymmetric between electric masking and acoustic masking was observed. Moreover, we investigated electric acoustic interaction through peripheral electrophysiological measures such as intracochlear ECochG and evoked action potentials (ECAPs). These previous works demonstrate that the interaction already exists at peripheral level, but psychoacoustic interaction cannot be explained only at the periphery. The interaction between electric and acoustic stimulation has been used to design a novel fitting for CIs. This novel fitting termed UNMASKfit achieves the same performance as the clinical standard fitting while requiring less stimulation at the apex of the cochlea. Moreover the study showed a decrease in performance if all the bandwidth is transmitted electrically and acoustically. For this reason, an outcome of this project is the recommendation to separate the bandwidth transmitted electrically and acoustically for CI users with residual hearing. More concrete, it is recommended to restrict the bandwidth transmitted electrically to frqeueneis above the cut-off frequency of acoustic stimulation. This result was confirmed in a second study in which interaction was maximized through phantom or partial tripolar stimulation. This second study also offered an alternative mode of stimulation for subjects that have progressive hearing loss and for which phantom stimulation can substitute to some extent their low frequency acoustic hearing. Computational models are essential to understand the measures obtained. In this context, we developed a computational model of a single auditory nerve fiber excited by electric and acoustic stimulation. The computational model combined with electrophysiological measurements offer the possibility to separate for the first time the contributions of the different neural generators of the peripheral interaction between electric and acoustic hearing that can potentially be used to understand de fundamental mechanisms of electric and acoustic stimulation and improve diagnostics and treatment devices for hearing loss.

Publications

• Simultaneous masking between electric and acoustic stimulation in cochlear implant users with residual low-frequency hearing. Hearing Research, 353, 185-196.
  Krüger, Benjamin; Büchner, Andreas & Nogueira, Waldo
  
• Electric-acoustic forward masking in cochlear implant users with ipsilateral residual hearing. Hearing Research, 364, 25-37.
  Imsiecke, Marina; Krüger, Benjamin; Büchner, Andreas; Lenarz, Thomas & Nogueira, Waldo
  
• Contralateral suppression of human hearing sensitivity in single-sided deaf cochlear implant users. Hearing Research, 373, 121-129.
  Nogueira, Waldo; Krüger, Benjamin; Büchner, Andreas & Lopez-Poveda, Enrique
  
• Interaction Between Electric and Acoustic Stimulation Influences Speech Perception in Ipsilateral EAS Users. Ear & Hearing, 41(4), 868-882.
  Imsiecke, Marina; Krüger, Benjamin; Büchner, Andreas; Lenarz, Thomas & Nogueira, Waldo
  
• Amplitude growth of intracochlear electrocochleography in cochlear implant users with residual hearing. The Journal of the Acoustical Society of America, 147(2), 1147-1162.
  Krüger, Benjamin; Büchner, Andreas; Lenarz, Thomas & Nogueira, Waldo
  
• Electric-acoustic interaction measurements in cochlear-implant users with ipsilateral residual hearing using electrocochleography. The Journal of the Acoustical Society of America, 147(1), 350-363.
  Krüger, Benjamin; Büchner, Andreas; Lenarz, Thomas & Nogueira, Waldo
  
• Psychoacoustic and electrophysiological electric-acoustic interaction effects in cochlear implant users with ipsilateral residual hearing. Hearing Research, 386, 107873.
  Imsiecke, Marina; Büchner, Andreas; Lenarz, Thomas & Nogueira, Waldo
  
• The role of electroneural versus electrophonic stimulation on psychoacoustic electric-acoustic masking in cochlear implant users with residual hearing. Hearing Research, 395, 108036.
  Kipping, Daniel; Krüger, Benjamin & Nogueira, Waldo
  
• Phantom Stimulation for Cochlear Implant Users With Residual Low-Frequency Hearing. Ear & Hearing, 43(2), 631-645.
  Krüger, Benjamin; Büchner, Andreas & Nogueira, Waldo
  
• A Computational Model of a Single Auditory Nerve Fiber for Electric-Acoustic Stimulation. Journal of the Association for Research in Otolaryngology, 23(6), 835-858.
  Kipping, Daniel & Nogueira, Waldo