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Electrophysiological and Psychophysical Electric-Acoustic Forward Masking in EAS Users
18 April 2018 (online)
Cochlear implant (CI) users with ipsilateral residual hearing combine acoustic and electric stimulation in one ear both (EAS). In EAS users, forward masking can be shown for electric probes following acoustic maskers and vice versa. The stage at which interaction between the two modalities takes place is so far unclear. In CI users with residual hearing it is possible to record intracochlear potentials with a high spatial resolution via the implanted electrode array. An investigation of the electrophysiological effects during combined electric-acoustic stimulation in humans might be used to assess peripheral mechanisms of masking. Nine MED-EL Flex electrode users with ipsilateral residual hearing participated in an electric-acoustic forward masking experiment. Psychoacoustic methods were used to measure the changes in thresholds due to the presence of maskers. Neural response telemetry was used to obtain electrically evoked compound action potentials (ECAP) for electric-only and for combined electric-acoustic presentation.
Behavioral thresholds of probe tones, either electric or acoustic, were significantly elevated in the presence of acoustic or electric maskers, respectively. Electric-on-acoustic forward masking showed more pronounced but shorter masking effects. So far electrophysiological measurements could be obtained from one subject during combined electric-acoustic stimulation. Preliminary analysis of these results shows a change in ECAP amplitude due to additional acoustic stimulation, which might depend on the phase of the additional acoustic stimulation. This indicates that peripheral masking effects might have been observed.
No conflict of interest has been declared by the author(s).