Optical Approaches for Neuroprosthetic Stimulation and Chronic Visualization of Sound Processing in the Adult Auditory System
CitationHight, Ariel. 2019. Optical Approaches for Neuroprosthetic Stimulation and Chronic Visualization of Sound Processing in the Adult Auditory System. Doctoral dissertation, Harvard University, Graduate School of Arts & Sciences.
AbstractDisabling hearing loss affects approximately 433 million people world-wide, resulting in impaired speech comprehension and associated hearing disorders including tinnitus and hyperacusis. Auditory multi-channel neuroprosthetic devices are widely used bioengineering solutions for sensory restoration. Auditory neuroprosthetics bypass sensory cells or primary neurons in the inner ear to directly stimulate early stages of the auditory pathway. These devices reliably restore the perception of auditory environmental awareness but have a mixed record of success in restoring unaided speech cues that form the basis of inter-personal communication. This dissertation uses rodent models to explore new approaches for stimulating the central auditory pathway and new approaches to understand how the auditory regions of the brain reorganize after hearing loss. In chapters 1-3, we describe efforts to identify neural bottlenecks in providing usable auditory cues through electrical stimulation of the brainstem and describe efforts to improve the spatial resolution of stimulation through optogenetic stimulation. In chapter 4, we describe a new approach for studying the organization of sound frequency representations in the auditory cortex using chronic widefield epifluorescence imaging of genetically encoded calcium indicators. In chapter 5, we leverage this long-term imaging approach to study the dynamics of compensatory plasticity following sudden acoustic trauma and associate these cortical dynamics with commensurate behavioral changes in loudness perception. Taken together, these studies suggest that optical stimulation of genetically encoded opsins represents a promising candidate for improving the spatial specificity of auditory neuroprostheses. On the flip side of the coin, optical approaches to track daily dynamics in sound processing across large brain regions with high resolution will provide deeper insight into the downstream processing of sound features after sensorineural hearing loss. The dissertation discusses how neuroprosthetic stimulation strategies guided by the abstracted modes of sound processing observed later in the auditory pathway rather than low-level auditory biophysics could introduce a new chapter in the implementation of sensory restoration devices.
Citable link to this pagehttp://nrs.harvard.edu/urn-3:HUL.InstRepos:42013137
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