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Polarity Sensitivity of Human Auditory Nerve Fibers Based on Pulse Shape, Cochlear Implant Stimulation Strategy and
Amirreza Heshmat1,2, Sogand Sajedi1, Anneliese Schrott-Fischer2
1Institute for Analysis and Scientific Computing, Vienna University of Technology, Vienna, Austria.
Frontiers in Neuroscience
|December 27, 2021
Summary
Investigating neural health in cochlear implant (CI) users using polarity sensitivity reveals that asymmetric pulses and multipolar stimulation strategies effectively distinguish auditory nerve fiber (ANF) degeneration patterns.
Area of Science:
- Computational neuroscience
- Biomedical engineering
- Auditory neurophysiology
Background:
- Neural health assessment is crucial for improving speech perception in cochlear implant (CI) users.
- Polarity sensitivity is a promising but complex method for evaluating auditory nerve fiber (ANF) status.
- Existing studies show contradictory results regarding polarity sensitivity behavior in CI users.
Purpose of the Study:
- To computationally investigate factors influencing polarity sensitivity in human auditory nerve fibers (ANFs).
- To model ANF degeneration patterns and their impact on neural responses to CI stimulation.
- To identify optimal stimulation parameters for distinguishing ANF degeneration levels.
Main Methods:
- Developed an accurate 3D finite element model of the human cochlea with realistic ANFs.
- Simulated ANF degeneration by reducing axon diameter and myelination thickness.
- Analyzed polarity sensitivity under varying pulse shapes (symmetric/asymmetric), stimulation strategies (monopolar/multipolar), and array positions (perimodiolar/lateral).
Main Results:
- Action potential initiation sites were primarily peripheral in lateral arrays but varied in perimodiolar arrays based on stimulation parameters.
- Clustering of threshold values in perimodiolar arrays with multipolar strategies occurred only with asymmetric pulses.
- Polarity trends differed: perimodiolar arrays showed declining polarity with degeneration (multipolar, asymmetric pulses), while lateral arrays exhibited shifts from cathodic to anodic sensitivity with increasing degeneration.
Conclusions:
- Asymmetric pulse shapes combined with multipolar stimulation strategies are effective for distinguishing ANF degeneration patterns.
- The distance to the modiolus wall is a critical factor in interpreting polarity sensitivity.
- This computational approach provides insights into optimizing CI strategies for personalized neural health assessment.
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