Multisensory Processing: Plasticity & Accommodation to a Sensory Prosthesis

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The goals of this research program are to investigate behavioral and neural consequences of lifelong sensory deprivation and relate those consequences to the potential to induce normal function in neural circuits following implantation of a sensory prosthesis. The fundamental hypotheses guiding the research plan are that: Lifelong sensorineural hearing impairment exerts profound multisensory effects on brain organization and function; Thus, the outcome of receiving a cochlear implant to induce hearing in adulthood will depend on multisensory cortical plasticity and processing. Prelingually deaf adults who are cochlear implant patients at the House Clinic will be enrolled in experiments that use behavioral, electrophysiological and functional magnetic resonance imaging (fMRI) methods to investigate multisensory (visual, vibrotactile, and auditory) processing before and after cochlear implantation. Speech and non-speech multisensory perceptual effects will be investigated. Controls will be normal-hearing adults. Experiments will investigate (1) audiovisual speech perception using behavioral methods at pre- and post-cochlear implantation; (2) Cortical activity in response to vibrotactile, visual, and visual-tactile speech stimuli, using fMRI before implantation; (3) Audiovisual versus auditory-only spoken word learning following implantation, using a behavioral training paradigm; (4) Multisensory audiovisual and visual-tactile stimulus detection before and after cochlear implantation, using event-related potentials (ERPs) from electroencephalographic (EEG) data; and (5) Multisensory event perception before and after cochlear implantation using behavioral, fMRI, and ERP data. Modeling methods for ERP data with constraints from anatomical and functional MRI will be used in order to achieve high spatial and temporal resolution data on cortical activity, and also to overcome limitations on the use of MRI following cochlear implantation. Comprehensive subject and device data will be obtained from patients to be used in conjunction with statistical analyses on experimental data and also to create a normative database on this clinical population. Relevance to Public Health: This project addresses fundamental questions about neural plasticity in adults. It explicitly tests a multisensory approach to sensory training that could generalize to other sensory disorders such as blindness. The project integrates basic science with ongoing clinical practice and with graduate student training.