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.
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/cm2 (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.
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. Lasers Surg. Med. 38:745–753, 2006. © 2006 Wiley-Liss, Inc.