IN SITU ANALYSIS OF INTRACOCHLEAR ELECTRODE POSITION

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Cochlear implants are now seen as an effective clinical strategy for enhancing communication in the profoundly hearing impaired. Estimates suggest that over 150,000 patients worldwide have been implanted to date. The efficacy of this approach is, however, highly variable across patients. Animal behavioral studies have likewise shown significant inter-subject variability in psychophysical measures of implant performance. Numerous factors have been hypothesized to play roles in this variability. These factors include, but are not limited to, electrode design and configuration, overall variations in neural survival, local variations in neural density relative to electrode contacts, intracochlear location of stimulating contacts and variations in the distance between electrode contacts and the target neural elements. The goal of our reseach program has been to study systematically the relationship between electrode position within the cochlea and measures of implant performance. We have carried out extensive, long-term behavioral and electrophysiological testing in our long-term (6+ years), behaviorally-trained and implanted animals under our NIH-R01.( NIH asked us to recompete the grant from UF and a competing renewal application is currently being prepared). To determine the precise location of each electrode contact within the cochlea requires a combination of techniques; MRM for the critical anatomical details and TACT for the fine electrode details. At present we are working with Dr. Richard Webber (Bowman Gray Medical Center; developer of TACT) and Dr. Madhu Nair (University of Florida; a leading authority on TACT applications) to optimize TACT imaging parameters to image the arrays in vivo and, in situ after the animals have been sacrificed. While TACT can provide the highest resolution images of the implanted electrode array, it is not capable of imaging the fine bony structures and tissues of the inner ear.