Comparing Patient-Specific Variations in Intra-Cochlear Neural Health Estimated Using Psychophysical Thresholds and...

Area of Science:

• Audiology
• Neuroscience
• Biomedical Engineering

Background:

• Neural survival variations along cochlear implant (CI) electrode arrays cause off-place listening.
• This leads to reduced speech understanding in CI recipients.
• Clinically viable tests are needed to identify patient-specific intra-cochlear neural differences.

Purpose of the Study:

• To compare two methods for estimating neural health along the CI electrode array.
• To investigate the correlation between these neural health estimates.
• To determine if variations in neural health correlate with speech understanding outcomes.

Main Methods:

• Nineteen experienced adult CI recipients participated.
• Neural health was estimated using psychophysical detection thresholds (bipolar vs. monopolar modes) and panoramic electrically evoked compound action potential (PECAP).
• Correlations between methods and with speech scores were analyzed.

Main Results:

• Individual-level correlations between the two neural measures were significant for 5 out of 15 participants.
• A weak but significant group-level correlation was found between the methods.
• Greater variation in psychophysical thresholds correlated with lower phoneme speech scores (R²=0.499, p<0.01), but PECAP variations did not.

Conclusions:

• Both methods likely assess a shared neural basis along the CI array.
• Differences in results may stem from stimulus parameters or central neural influences.
• Psychophysical thresholds may be more sensitive to variations impacting speech outcomes.