Electrode-specific ECAP Amplitude Growth Functions and their relationship to psychophysically determined loudness growth on the same electrodes

Background and significance In CI subjects, an instantaneous compression curve maps the filter outputs to currents within the electrical dynamic range. The same compression curve is being used for all electrode contacts alike, not taking into account possible differences in the loudness growth functions (LGF) across electrodes. We investigate the correlation between the subjectively perceived LGF and the evoked compound action potential amplitude growth function (ECAP AGF). In case there was a good correlation between the two, an automatically determined ECAP AGF might be used to predict the shape of the loudness growth curve of each individual channel allowing for an automated individualization of the compression curves.

Material and methods 0 MedEl CI subjects with fully inserted long electrode arrays (standard 31mm or Flex 28) have been recruited for the study. ECAPs are measured using the AutoART function within the clinical fitting software Maestro, while the LGFs are determined using the psychophysical software suite PsyWorks. Subjects have to indicate the perceived loudness of each stimulus on a continuous scale from “inaudible” to “too loud”.

Results The slope of the ECAP AGF as well as the subjective LGF seems to be subject and electrode specific and both curves become shallower towards the base of the cochlear, indicating a place dependency. For selected electrodes, we found a significant correlation between the steepness of the subjective LGF and the ECAP AGF.

Conclusion Our outcomes speak in favor of an individualized compression function for each individual channel in cochlear implant systems which might in fact be achievable using an objective ECAP-AGF based approach.

Poster-PDF A-1856.PDF

Publication History

Article published online:
10 June 2020