Characterization of single auditory nerve fibers in response to laser stimulation

One drawback with traditional cochlear implants, which use electrical currents to stimulate spiral ganglion cells, is the ability to stimulate spatially discrete cells without overlap and electric current spread. We have recently demonstrated that spatially selective stimulation of the cochlea is possible with optical stimulation. However, for light to be a useful stimulation paradigm for stimulation of neurons, including cochlear implants, the neurons must be stimulated at high stimulus repetition rates. In this paper we utilize single fiber recordings from the auditory nerve to demonstrate that stimulation is possible at high repetition rates of the light pulses. Results showed that action potentials occurred 2.5-4. ms after the laser pulse. Maximum rates of discharge were up to 300 Hz. The action potentials did not respond strictly after the light pulse with high stimulation rates, i.e. >300 pulses per second. The correlation between the action potentials and the laser pulses decreased drastically for laser pulse repetition rate larger than 300 pulses per second.