It is not fully understood how spatial and temporal patterns of microstimulation of primary auditory cortex affect the quality of percept. The principle goal of this application is to use behavioral assays in rats to investigate the limits of sensory perceptions evoked by spatial patterns of intracortical microstimulation (ICMS) through multiple tetrode arrays implanted in primary auditory cortex of deafened rat. This application will determine if perceptual differences exist between monopolar and tripolar microstimulation of auditory cortex, and examine the quality of ICMS within (35 - 50 micrometers) and between (100 - 250 micrometers) tetrodes, through behavior. The use of behaviorally conditioned animals has the potential to be a strong indication of the quality of percept elicited by multi-site patterned microstimulation. The spatial limits of electrically-evoked auditory percepts determined through this application will aid in the design of future cortical neuroprosthetics. This work is of potentially great relevance in the development and design of an electrical brain-machine interface capable of stimulating auditory cortex in such a manner as to artificially evoke auditory perceptions.