Apparatus and method for optical- or optical-and-electrical stimulation of midbrain and/or brainstem tissue (e.g., auditory nerve pathways). Peripheral neural stimulation using infrared lasers has been demonstrated in several systems; however, optical stimulation of the central nervous system (CNS) has not been previously described. In some embodiments of the present invention, radiant energy exposure of the cochlear nucleus using a mid-wavelength infrared laser generates optically-evoked auditory brainstem responses (oABRs). In an experiment, the cochlear nuclei of adult male Sprague-Dawley rats were exposed using a suboccipital craniotomy approach. In one embodiment, different regions of left cochlear nucleus were acutely stimulated with a 200- or 400-micron-diameter optical fiber placed on the surface of the brainstem, using 50- to 750-microsecond pulses of 1849-nm to 1865-nm-wavelength radiation at a rate of 10 to 40 Hz and power levels ranging from 10% to 80% of 5 watts. oABRs were recorded during the period of optical stimulation.
Optical stimulation of the brainstem and/or midbrain, including auditory areas