The depth, waveform and pulse rate for electrical microstimulation of the auditory cortex

Intracortical microstimulation of primary sensory regions of the brain offers a compelling platform for the development of sensory prostheses. However, fundamental questions remain regarding the optimal stimulation parameters. The purpose of this paper is to summarize a series of experiments which were designed to answer the following three questions. 1) What is the best electrode implantation depth? 2) What is the optimal stimulation waveform? 3) What is the maximal useful stimulus pulse rate? The present results suggest the following answers: 1) cortical layers V&IV, 2) biphasic, charge balanced, symmetric, cathode leading pulses with of duration of ∼ 100 microseconds per phase, and 3) 80 pulses-per-second.