Neural sensitivity in cochlear implantees determined by electrically-evoked compound action potentials (ECAP) and...

The sensitivity of auditory neurons in response to electric stimulation in cochlear implant (CI) listeners may reflect neuronal health, which is a major contributor to variability in performance outcomes among CI listeners. In the current study, we explore the interplay of three outcome measures of neural sensitivity, perceptual focused thresholds, objective electrically-evoked compound action potentials (ECAP), and the Failure Index (FI). We further explore the influence of CI experience and how the measures may contribute to speech perception performance.

We examined focused perceptual threshold measures, ECAP stimulation levels and N ₁ P ₂ peak response amplitudes, and ECAP input-to-output relationships in 29 adult CI recipients (14 females, 11 males, four who were bilaterally implanted). Pearson correlation analysis was performed to investigate subject specific relationships across CI electrodes, and linear mixed-effects models (LMM) were used to identify links between the outcome measures accounting for individual variation.

Individual outcomes revealed large within and across subject variability for focused thresholds, ECAP peak amplitudes, and FI. The LMMs showed, that low focused threshold measurements correspond to large ECAP peak amplitudes, while high ECAP stimulation levels reflect large ECAP peak amplitudes. Furthermore, clinical speech perception seems to be influenced by the relationship of focused thresholds and FI, with lower performance for stronger associations.

Our findings suggest that the combination of objective ECAP response measures and perceptual measures could be a robust estimate of neural health and may act as an early estimate of the speech performance abilities in CI listeners.