Multisensory Integration and Neuroplasticity in Adults with Cochlear Implants

Abstract

Cochlear implants (CIs) can restore hearing in adults with sensorineural hearing loss, yet speech recognition outcomes vary widely among users. This variability highlights the need for improved rehabilitation strategies and a deeper understanding of the mechanisms driving speech recovery. This thesis examines two relatively underappreciated factors that contribute to CI outcomes: multisensory integration and neuroplasticity. Traditional assessments of CI success focus exclusively on auditory-only speech measures. However, everyday communication is inherently multisensory, and visual cues can be especially helpful when listening in noisy environments or listening with a CI. Additionally, clinical interventions for hearing loss have historically targeted the inner ear, either by amplifying sound (hearing aids) or directly stimulating the auditory nerve (CIs). Emerging research suggests that hearing loss has impacts beyond the cochlea, involving neuroplastic changes throughout the auditory pathway and extending into multisensory brain networks. Recognizing this broader framework opens novel avenues for intervention. This thesis investigates the impact of multisensory integration training on speech comprehension in both adults with typical hearing and CIs. It also explores the role of cholinergic modulation in sensory perception, culminating in a randomized controlled trial assessing the effects of donepezil on speech understanding in adults with CIs. Our preliminary findings suggest that audiovisual training and cholinergic augmentation enhance speech processing by promoting plasticity in cortical speech networks. By applying a holistic view of the auditory system and integrating multisensory rehabilitation strategies with pharmacological approaches that enhance cortical plasticity, we aim to enhance auditory rehabilitation and optimize speech outcomes for adults with CIs.