Graduate Training in Neuroscience
University of Washington
Julie A. Bierer
Associate Professor, Speech and Hearing Sciences
Research in my lab uses multiple methods to address a couple of questions about cochlear implants and how they interface to the auditory system. In multi-channel cochlear implants, each electrode will interface to nearby neurons in a particular way and the quality of that interface depends on several factors including; how the electrical current is directed to the neurons, the local neural survival pattern, the position of the cochlear implant within the cochlea, bone and tissue growth, etc. Using psychophysical methods, we use highly focused electrical stimulation to probe the cochlea and assess local electrode-neuron interfaces. We then characterize channels believed to have a poor or a good interface by measuring behavioral and evoked potential thresholds, behavioral growth of loudness and amplitude growth functions of evoked potentials, psychophysical tuning properties and temporal modulation detection. In addition, we are developing a practical model of cochlear implant activation of the auditory nerve in the presence of varying nerve survival and/or distance between the electrode and nerve. The ability for broad (monopolar) and restricted (tripolar) configurations to detect regions of poor nerve survival will be assessed. A monopolar-tripolar hybrid configuration, partial tripolar, will also be evaluated. The model will be tested and modified to fit data from cochlear implant listeners. The long-range goal is for audiologists to have a tool to map the cochlear implant electrode relative to viable nerve cells with the threshold measures. Finally, in animal models, neurophysiological experiments are performed to characterize novel cochlear implant stimuli by measuring neural activation patterns of the central auditory nervous system using multi-channel recording techniques.