Phoneme-related potentials recorded from normal hearing listeners and cochlear implant users in a selective attention paradigm to continuous speech.

Cochlear implants can restore the ability to understand speech in patients with profound sensorineural hearing loss. At present, it is not fully understood how cochlear implant users perceive speech and how electric hearing provided by a cochlear implant differs from acoustic hearing. Phoneme-related potentials characterize neural responses to individual instances of phonemes extracted from continuous speech. This retrospective study investigated phoneme-related potentials in cochlear implant users in a selective attention paradigm. Responses were compared between normal hearing listeners and cochlear implant users, and between attended and unattended conditions. Differences between phoneme categories were compared and a classifier was trained to predict the phoneme category from the neural representation. The phoneme-related potentials of cochlear implant users showed similar responses to the ones obtained in normal hearing listeners for early responses (< 100 ms) but not for later responses (> 100 ms) where peaks were smaller or absent. Attention led to an enhancement of the response, whereas latency was mostly not affected by attention. The temporal morphology of the response was influenced by the phonetic features of the stimulus, allowing a classification of the phoneme category based on the phoneme-related potentials. There is a clinical need for methods that can rapidly and objectively assess the speech understanding performance of cochlear implant users. Phoneme-related potentials may provide such a link between the acoustic and the neural representations of phonemes. They may also reveal the challenges of individual subjects and thus provide indications for patient-specific auditory training, rehabilitation programs or the fitting of cochlear implant parameters.