In vivo auditory nerve stimulation with visible light

Background:Infrared laser stimulation has been proposed as an innovative method to elicit an auditory nerve response.Most studies have focused on usi ng long-wavelength infrared(>980 nm)pulsod lasers with high water absoption cofficients.This paper sought to assts8 whether a short-wavelength laser(465 nm)with an absorption cofficient as low as 103 cm^(-1) would activate the auditory nerve and studied its potential mechanism.Method:Optical compound action potentials(OCAPs)were recorded when synchronous triger laser pulses st imulate the cochlea before and after deafening,varying the pulse durations(from 8001us to 36001us)and the amount of radiant enengy(fom 18.05 mJ/cm^(2) to 107.91 mJ/cm^(2)).A thermal infrared imager was applied to monitor the tempenature change of the guinea pig cochlea.Results:The results showed that pulsed laser stimulation at 465 nm could invoke OCAPs and had a similar waveform compared to the acoustical compound action potentials.The amplitude of OCAPs had a poaitive correlation with the in-creasi ng laser peak power,while the latency of OCAPs showed a negative correlation.The imager data showed that the temperature in thecochlea rose quickly by about 0.3℃ right after stimulating the cochlea and decreased quickly back to the initial temperature as the stimulation ended.Con-clusions:This paper demonstrates that 465-nm laser st imulation can successfully induce OCAPs outside the cochlea,and that the amplitude and latency of the invoked OCAPs are highly affected by laser peak power.This paper proposes that a photothermal efect might be the main mechanism for the auditory nerve response induced by short-wavelength laser stimulation.