Light can artificially stimulate nerve activity in vivo. A significant advantage of optical neural
stimulation is the potential for higher spatial selectivity when compared with electrical stimulation.
An increased spatial selectivity of stimulation could improve significantly the function of
neuroprosthetics, such as cochlear implants. Cochlear implants restore a sense of hearing and
communication to deaf individuals by directly electrically stimulating the remaining neural cells in
the cochlea. However, performance is limited by overlapping electric fields from neighboring
Here, we report on experiments with a new laser, offering a previously unavailable
wavelength, 1.94μm, and pulse durations down to 5μs, to stimulate cochlear neurons. Compound
action potentials (CAP) were evoked from the gerbil cochlea with pulse durations as short as 1μs.
Data show that water absorption of light is a significant factor in optical stimulation, as evidenced by
the required distance between the optical fiber and the neurons during stimulation. CAP threshold
measurements indicate that there is an optimal range of pulse durations over which to deposit the
laser energy, less than ~100μs. The implications of these data could direct further research and
design of an optical cochlear implant.