title: Acoustic events and "optophonic" cochlear responses induced by pulsed near-infrared laser.
abstract: Optical stimulation of neural tissue within the cochlea was described as a possible alternative to electrical stimulation. Most optical stimulation was performed with pulsed lasers operating with near-infrared (NIR) light and in thermal confinement. Under these conditions, the coexistence of laser-induced optoacoustic stimulation of the cochlea ("optophony") has not been analyzed yet. This study demonstrates that pulsed 1850-nm laser light used for neural stimulation also results in sound pressure levels up to 62 dB peak-to-peak equivalent sound pressure level (SPL) in air. The sound field was confined to a small volume along the laser beam. In dry nitrogen, laser-induced acoustic events disappeared. Hydrophone measurements demonstrated pressure waves for laser fibers immersed in water. In hearing rats, laser-evoked signals were recorded from the cochlea without targeting neural tissue. The signals showed a two-domain response differing in amplitude and latency functions, as well as sensitivity to white-noise masking. The first component had characteristics of a cochlear microphonic potential, and the second component was characteristic for a compound action potential. The present data demonstrate that laser-evoked acoustic events can stimulate a hearing cochlea. Whenever optical stimulation is used, care must be taken to distinguish between such "optophony" and the true optoneural response.
authors.affiliation: Institute of Audioneurotechnology, Hannover School of Medicine, Hannover, Germany. teudt.ingo@mh-hannover.de
authors.forename: Ingo Ulrik
authors.initials: IU
authors.lastname: Teudt
authors.forename: Hannes
authors.initials: H
authors.lastname: Maier
authors.forename: Claus-Peter
authors.initials: CP
authors.lastname: Richter
authors.forename: Andrej
authors.initials: A
authors.lastname: Kral
mesh_terms: D000161:Acoustic Stimulation / Q000295:instrumentation* / Q000379:methods*; D000818:Animals; D003051:Cochlea / Q000502:physiology*; D005072:Evoked Potentials, Auditory / Q000502:physiology*; D006310:Hearing Aids; D007259:Infrared Rays; D007834:Lasers; D051381:Rats; D017207:Rats, Sprague-Dawley