Background and objectives: For centuries, electric current has been used to stimulate neurons. Shortcomings of electrical stimulation include the contact between the stimulating electrode and the tissue, and the non-selective stimulation of the tissue. In contrast to electric stimulation, optical radiation can provide spatially selective neural stimulation without tissue contact.
Study design/materials and methods: Acute in vivo experiments using gerbils were conducted to record optically evoked compound action potentials (CAPs) from the cochlea.
Results: Optical radiation evokes CAPs in normal hearing animals and in deafened animals, in which cochleae lack outer and inner hair cells. Stimulation threshold was measured as 0.018+/-0.003 J/cm(2) (mean+/-SE). Laser radiation could be increased by 30-40 dB until drastic changes were seen in cochlear function. Cochlear response amplitudes to optical radiation were stable over extended stimulation times.
Conclusions: We have demonstrated that the auditory nerve can be stimulated by optical radiation. One potential clinical use of this technology would be for cochlear implants.
(c) 2006 Wiley-Liss, Inc.