| Disorders of the human nervous system typically result in disabilities and ailments that significantly lower the quality of life for the afflicted individuals. Neural prostheses have emerged in an effort to alleviate some or all of these ailments. One branch of neural prosthetic research aims to restore sensory function due to congenital defects, disease, or injury. Specifically related to this project, cortical stimulation of the primary auditory cortex has been postulated to be a potential mode of operation for an auditory prosthesis. Several historical studies have shown that auditory cortex surface stimulation is inadequate due to the dangerously high threshold currents needed and poor stimulation specificity. Recent advances in neural interface technology, combined with pilot studies conducted in the visual cortex of primates and humans, validate investigations of intracortical microstimulation in auditory cortex as a mode of operation for an auditory prosthesis.; The specific aims of this research were to develop and validate an animal model for an intracortical auditory prosthesis and to evaluate the capacity of this technique to provide multi-channel information transfer through a chronically implanted brain machine interface. First, a rat-based animal model was developed utilizing a chronic, penetrating microelectrode array. This animal model was successfully validated via behavioral measurements of the ability of the subject to detect single-channel electrical microstimulation. Second, in an effort to further elucidate the sensory parameters of the microstimulation, behavioral results were evaluated in an auditory frequency discrimination task. The results suggest that parameters of the sensation elicited by micro stimulation are related to electrophysiological properties of the tissue proximal to the implanted electrode. Lastly, the behavioral salience of the micro stimulation-induced sensation was evaluated relative to natural, auditory-induced sensations. In both detection- and discrimination-based behavioral settings, microstimulation cues resulted in better performance of the task. Further, microstimulation as closely spaced as 250 microns produced significantly different behavior. These results are consistent with recent reports that sensory intracortical microstimulation provides robust, salient cues in a behavioral setting. Further, these results have implications for the feasibility and development of a cortical sensory prosthesis. |
