Toward individualized cochlear implant programming: Relating electrophysiological and psychophysical indicators of tonotopic region performance

This study compared outcomes of two electrophysiological measures, electrocochleography (ECochG) and panoramic electrically-evoked compound action potential (PECAP), and two psychophysical measures, temporal and electrode discrimination test (TED) and spectrotemporal two-octave bandpass modulation test (STM), in cochlear implant (CI) listeners. The aim was to investigate whether tonotopic regions showing poorer performance on the acoustic STM test also exhibit reduced peripheral integrity (ECochG and PECAP) or diminished modulation encoding abilities at the electrode level (TED). Twenty-seven Advanced Bionics CI candidates were prospectively enrolled prior to CI surgery. ECochG and PECAP recordings were obtained from all intracochlear electrodes intraoperatively and three months post-implantation, respectively. TED was measured via direct electrode stimulation six months post-implantation, and the STM test was conducted with CI-processed acoustic stimulation one year after surgery. All measures were obtained or averaged across four tonotopic regions. After adjusting for region-specific CI-processing differences, linear mixed model analyses showed significantly poorer STM performance in the worst-performing region compared with the other three regions (p < 0.001). TED values were also significantly worse in this region (p < 0.01), whereas ECochG and PECAP values did not differ significantly between the worst region on the STM test and the remaining regions. These findings demonstrate that while electrophysiological and psychophysical measures each provide valuable, spatially specific information, they capture distinct physiological and perceptual aspects of auditory processing. This highlights the need to investigating which measure, or combination of measures, can best guide individualized CI programming adjustments by identifying suboptimal performing tonotopic regions.