Optical Stimulation of the Auditory Nerve: Effects of Pulse Shape

It has been demonstrated that spiral ganglion cells in the cochlea can be stimulated with infrared radiation (IR). The potential benefits of infrared neural stimulation (INS) include the possibility of stimulating the neurons without direct physical contact between the stimulation source and the neural tissue and the improved spatial selectivity. In order to determine how INS can be best incorporated in both research and in neural interfaces, it is critical to identify the optimal stimulation parameters for the laser. This study focuses on direct comparison of amplitudes of neural responses evoked by various IR pulse shapes and durations. With the present experiments, the results indicate that the peak power is an important variable for stimulating auditory neurons. While the radiant energy has little effect on amplitudes of compound potentials (CAP) evoked by infrared pulses shorter than 70 mu s, it impacts the amplitudes for pulses 80 mu s and longer. In addition, we show that the shape of the infrared pulse is important and varying the shape may allow an expansion of response dynamic range while stimulating neurons. The results indicate that square pulses were the most effective pulse shape to evoke CAPs.