Laser stimulation of auditory neurons at high repetition rate

摘要

Pulsed, mid-infrared lasers can evoke neural activity from motor as well as sensory neurons in vivo. Lasers allow more selective spatial resolution of stimulation than the conventional electrical stimulation. To date, few studies have examined pulsed, mid-infrared neural stimulation and very little of the available optical parameter space has been studied. We found that pulse durations as short as 20 μs elicit a compound action potential from the gerbil cochlea. Moreover, stimulation thresholds are not a function of absolute energy or absolute power deposited. Compound action potential peak-to-peak amplitude remained constant over extended periods of stimulation. Stimulation occurred up six hours continuously and up to 50 Hz in repetition rate. Single fiber experiments were made using repetition rates of up to 1 kHz. Action potentials occurred 2.5-4 ms after the laser pulse. Maximum rates of discharge were up to 250 action potentials per second. With increasing stimulation rate (300 Hz), the action potentials did not respond strictly after the light pulse. The results from these experiments are important for designing the next generation of neuroprostheses, specifically cochlear implants.