Abstract
Background: Infrared laser stimulation has been proposed as an innovative method to elicit an auditory nerve response. Most studies have focused on using long-wavelength infrared ([Formula: see text][Formula: see text]nm) pulsed lasers with high water absorption coefficients. This paper sought to assess whether a short-wavelength laser (465[Formula: see text]nm) with an absorption coefficient as low as 10[Formula: see text][Formula: see text]cm[Formula: see text] would activate the auditory nerve and studied its potential mechanism. Method: Optical compound action potentials (OCAPs) were recorded when synchronous trigger laser pulses stimulate the cochlea before and after deafening, varying the pulse durations (from 800[Formula: see text][Formula: see text]s to 3600[Formula: see text][Formula: see text]s) and the amount of radiant energy (from 18.05[Formula: see text]mJ/cm2 to 107.91[Formula: see text]mJ/cm2). A thermal infrared imager was applied to monitor the temperature change of the guinea pig cochlea. Results: The results showed that pulsed laser stimulation at 465[Formula: see text]nm could invoke OCAPs and had a similar waveform compared to the acoustical compound action potentials. The amplitude of OCAPs had a positive correlation with the increasing laser peak power, while the latency of OCAPs showed a negative correlation. The imager data showed that the temperature in the cochlea rose quickly by about 0.3[Formula: see text]C right after stimulating the cochlea and decreased quickly back to the initial temperature as the stimulation ended. Conclusions: This paper demonstrates that 465-nm laser stimulation 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 effect might be the main mechanism for the auditory nerve response induced by short-wavelength laser stimulation.
Highlights
According to the World Health Organization, $360 million people su®er from disabling hearing impairment, which can cause social isolation, reduced professional capabilities, and other social problems.[1]
We analyzed the optical and acoustic compound action potentials (ACAPs) to determine whether stimulation at 465 nm could invoke an auditory response in deafened cochlea, and monitored the temperature change during stimulation to analyze the mechanism of generating optical compound action potentials (OCAPs)
Cochlear microphonic potentials were observed in ACAP curves before deafness, whereas no cochlear microphonic potentials were observed in OCAP curves in either group
Summary
Infrared laser stimulation has been proposed as an innovative method to elicit an auditory nerve response. This paper sought to assess whether a shortwavelength laser (465 nm) with an absorption coe±cient as low as 10À3 cmÀ1 would activate the auditory nerve and studied its potential mechanism. 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. Conclusions: This paper demonstrates that 465-nm laser stimulation can successfully induce OCAPs outside the cochlea, and that the amplitude and latency of the invoked OCAPs are highly a®ected. This is an Open Access article published by World Scientic Publishing Company. This paper proposes that a photothermal e®ect might be the main mechanism for the auditory nerve response induced by short-wavelength laser stimulation.
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