Assessing the Relationship Between Pitch Perception and Neural Health in Cochlear Implant Users
Neural health assessment in cochlear implant usersAbstract
Various neural health estimates have been shown to indicate the density of spiral ganglion neurons in animal and modeling studies of cochlear implants (CIs). However, when applied to human CI users, these neural health estimates based on psychophysical and electrophysiological measures are not consistently correlated with each other or with speech recognition performance.
This study investigated whether neural health estimates have stronger correlations with temporal and place pitch sensitivity than with speech recognition performance. On five electrodes in 12 tested ears of eight adult CI users, we measured polarity effect (PE), multipulse integration (MPI), and interphase gap (IPG) effect on the amplitude growth function (AGF) of electrically evoked compound action potential (ECAP) to estimate neural health, while thresholds of amplitude modulation frequency ranking (AMFR) and virtual channel ranking (VCR) were measured to indicate temporal and place pitch sensitivity.
Study at a Glance
Key Findings
Results
The results showed significantly poorer AMFR and VCR thresholds on basal electrodes compared to apical and middle electrodes. Across ears and electrodes, only the IPG offset effect on ECAP AGF had a nearly significant negative correlation with VCR threshold after removing outliers. No significant across-ear correlations were found between mean neural health estimates, mean pitch-ranking thresholds, and AzBio sentence recognition scores.
Clinical Implications
This study suggests that central axon demyelination reflected by the IPG offset effect may be important for place pitch sensitivity in CI users, and that the IPG offset effect may predict perceptual resolution of virtual channels for CI programming optimization.
Research Poster
Visual Summary
Methodology and results overview
