Patient-specific electrophysical and psychophysical characterisation of cochlear implant hearing for enhancement of pitch perception

There is a lot of variation between cochlear-implant (CI) patients, in their speech understanding, pitch perception, and their electrode-neuron interfaces. The research proposed will combine multiple electrophysiological and psychophysical techniques for characterisation of individual CI patients’ hearing, with a goal of leveraging highly-selective channels to investigate their ability to integrate pitch cues. I will measure electrically evoked compound action potentials (eCAPs) via reverse telemetry and use the Panoramic ECAP method to estimate current spread and neural responsiveness at the level of the auditory nerve. I will also use electroencephalography (EEG) to measure brainstem and cortical responses. I will include the ALternating Interleaved Frequency Electrical Stimulation (ALFIES) technique that will additionally provide a measure of spatial selectivity at the level of the cortex. I will then compare these electrophysiological data with psychophysics responses in the same CI users to characterise the number of perceptible rate-pitch and place-pitch steps. The pitch experiment will require CI users to indicate which of a pair of electrodes or rates has a higher pitch. Both the electrophysiological and psychophysical measures will identify highly selective channels for each individual CI user. These areas will then be targeted for two final experiments designed to investigate whether it is possible to integrate multiple place-pitch cues to detect a missing fundamental and/or a Zwicker tone. Together, these experiments will provide a dataset in which to compare electrophysiological measurements with behavioural reports of selectivity, pitch, and loudness, taking strides towards development of objective and fully-automated approaches for identifying threshold and comfort levels for CI programming. Additionally, they will provide insight into mechanisms of pitch perception, and possibly inform future signal processing techniques that could be leveraged in CI users’ programming strategies to enhance pitch cues and improve the salience of pitch-reliant cues like prosody, lexical tones, and music.