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Psychophysical versus physiological spatial forward masking and the relation to speech perception in cochlear
Michelle L Hughes1, Lisa J Stille
1Boys Town National Research Hospital, Lied Learning and Technology Center, Omaha, Nebraska.
Ear and Hearing
|March 18, 2008
Summary
Electrically evoked compound action potential (ECAP) forward masking (FM) patterns show moderate correlation with psychophysical forward masking (PFM) in cochlear implant users. However, ECAP FM alone cannot reliably predict individual PFM patterns or speech perception outcomes.
Area of Science:
- Auditory Neuroscience
- Biomedical Engineering
- Cochlear Implant Technology
Background:
- Cochlear implants (CIs) aim to restore hearing by electrically stimulating the auditory nerve.
- Understanding neural processing, like forward masking, is crucial for optimizing CI performance.
- Physiological measures offer objective insights into neural activity, complementing subjective psychophysical assessments.
Purpose of the Study:
- To investigate the predictive power of physiological forward masking (FM) patterns, measured via electrically evoked compound action potentials (ECAP), for psychophysical forward masking (PFM) patterns in CI users.
- To explore the relationship between spatial forward masking patterns and speech perception abilities in CI recipients.
- To determine if reduced channel interaction, assessed through ECAP or PFM, correlates with enhanced speech understanding.
Main Methods:
- Collected data from 18 adult cochlear implant recipients using two different CI models.
- Measured physiological spatial forward masking patterns using ECAP via the implant telemetry system.
- Obtained psychophysical forward masking (PFM) patterns using a three-interval, two-alternative forced-choice adaptive procedure with varied masker locations relative to a fixed probe electrode.
Main Results:
- A significant group correlation (r = 0.55, p < 0.0001) was found between ECAP FM and PFM patterns, particularly for basal electrodes.
- Individual correlations varied, with strong agreement in 10 subjects, moderate in two, and poor in six.
- No significant correlation was observed between speech perception scores and either ECAP FM or PFM patterns; conversely, good ECAP-PFM correlation was linked to poorer speech perception.
Conclusions:
- ECAP FM and PFM patterns demonstrated good correlation in two-thirds of the participants.
- Despite statistical significance, ECAP FM patterns explained only 30% of the variance in PFM measures.
- ECAP measures alone are insufficient for accurately predicting individual psychophysical forward masking patterns in cochlear implant users.
