Optoacoustic effect is responsible for laser-induced cochlear responses.
Optical stimulation of the cochlea with laser light has been suggested as an alternative to conventional treatment of sensorineural hearing loss with cochlear implants. The underlying mechanisms are controversially discussed: The stimulation can either be based on a direct excitation of neurons, or it is a result of an optoacoustic pressure wave acting on the basilar membrane. Animal studies comparing the intra-cochlear optical stimulation of hearing and deafened guinea pigs have indicated that the stimulation requires intact hair cells. Therefore, optoacoustic stimulation seems to be the underlying mechanism. The present study investigates optoacoustic characteristics using pulsed laser stimulation for in vivo experiments on hearing guinea pigs and pressure measurements in water. As a result, in vivo as well as pressure measurements showed corresponding signal shapes. The amplitude of the signal for both measurements depended on the absorption coefficient and on the maximum of the first time-derivative of laser pulse power (velocity of heat deposition). In conclusion, the pressure measurements directly demonstrated that laser light generates acoustic waves, with amplitudes suitable for stimulating the (partially) intact cochlea. These findings corroborate optoacoustic as the basic mechanism of optical intra-cochlear stimulation.
Laser Zentrum Hannover e.V., Hollerithallee 8, 30419 Hannover, Germany.|Cluster of Excellence "Hearing4all", Germany.
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Kallweit
Institute of Audioneurotechnology and Dept. of Experimental Otology, ENT Clinics, Hannover Medical School, Feodor-Lynen-Str. 35, 30625 Hannover, Germany.
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Baumhoff
Laser Zentrum Hannover e.V., Hollerithallee 8, 30419 Hannover, Germany.|Cluster of Excellence "Hearing4all", Germany.
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Krueger
Laser Zentrum Hannover e.V., Hollerithallee 8, 30419 Hannover, Germany.|Cluster of Excellence "Hearing4all", Germany.
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Tinne
Cluster of Excellence "Hearing4all", Germany.|Institute of Audioneurotechnology and Dept. of Experimental Otology, ENT Clinics, Hannover Medical School, Feodor-Lynen-Str. 35, 30625 Hannover, Germany.
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Kral
Laser Zentrum Hannover e.V., Hollerithallee 8, 30419 Hannover, Germany.|Cluster of Excellence "Hearing4all", Germany.
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Ripken
Cluster of Excellence "Hearing4all", Germany.|Institute of Audioneurotechnology and Dept. of Experimental Otology, ENT Clinics, Hannover Medical School, Feodor-Lynen-Str. 35, 30625 Hannover, Germany.
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Maier
D000161:Acoustic Stimulation / Q000379:methods*; D000200:Action Potentials; D000818:Animals; D003051:Cochlea / Q000502:physiology*; D005260:Female; D006168:Guinea Pigs; D006198:Hair Cells, Auditory; D007834:Lasers; D008297:Male