This application proposes the use of animal psychophysical techniques to explore the functional consequences of electrical and chemical stimulation of profoundly deaf individuals. The focus is specifically on the role of stimulation as possible retardants to the cell death and downregulation that may result in disadvantageous neural reorganization. Guinea pigs will be psychophysically trained with acoustic stimuli, then deafened bilaterally. One or both ears will be implanted with a multichannel scala tympani electrode array. Specific treatments involving electrical stimulation, chemical stimulation, combined electrical and chemical stimulation, or no stimulation will be administered for two months after deafening. Measures of detection threshold for specific electrical stimuli will then be used to monitor the functional condition of the auditory system following these treatments. These threshold functions were previously shown to be correlated with nerve survival patterns. Pulse-rate and electrode-place discrimination abilities in animals deafened and given no neural stimulation for the first two months after deafening will then be assessed and compared to those of animals that received electrical and/or chemical neural stimulation during this period. Spiral ganglion cell counts will also be taken after animals are sacrificed.
