Intracochlear near infrared stimulation: Feasibility of optoacoustic stimulation in vivo

Baumhoff, Peter; Kallweit, Nicole; Kral, Andrej

doi:10.1016/j.heares.2018.11.003

Cited by 27 publications

(40 citation statements)

References 36 publications

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“…Three important factors may contribute to the differences among the studies: (i) gerbils and guinea pigs have different slopes of their frequency‐to‐place map in the cochlear base (3,200 µm/octave in guinea pigs and 1,540 µm/octave in gerbils), (ii) the gerbils were normal‐hearing animals, while the guinea pigs had damaged cochleae, and (iii) in gerbils, the masker was an acoustic stimulus while in the guinea pig study the masker was a second optical source. In normal‐hearing animals, we assume that the photoacoustic effect [54–58], which occurs during laser stimulation, can contribute as well and the results in the gerbil are likely biased by an acoustic interaction between the stimuli.…”

Section: Discussionmentioning

confidence: 99%

Channel Interaction During Infrared Light Stimulation in the Cochlea

Agarwal

Tan

et al. 2021

Lasers Surg Med

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Background and Objectives The number of perceptually independent channels to encode acoustic information is limited in contemporary cochlear implants (CIs) because of the current spread in the tissue. It has been suggested that neighboring electrodes have to be separated in humans by a distance of more than 2 mm to eliminate significant overlap of the electric current fields and subsequent interaction between the channels. It has also been argued that an increase in the number of independent channels could improve CI user performance in challenging listening environments, such as speech in noise, tonal languages, or music perception. Optical stimulation has been suggested as an alternative modality for neural stimulation because it is spatially selective. This study reports the results of experiments designed to quantify the interaction between neighboring optical sources in the cochlea during stimulation with infrared radiation. Study Design/Materials and Methods In seven adult albino guinea pigs, a forward masking method was used to quantify the interaction between two neighboring optical sources during stimulation. Two optical fibers were placed through cochleostomies into the scala tympani of the basal cochlear turn. The radiation beams were directed towards different neuron populations along the spiral ganglion. Optically evoked compound action potentials were recorded for different radiant energies and distances between the optical fibers. The outcome measure was the radiant energy of a masker pulse delivered 3 milliseconds before a probe pulse to reduce the response evoked by the probe pulse by 3 dB. Results were compared for different distances between the fibers placed along the cochlea. Results The energy required to reduce the probe's response by 3 dB increased by 20.4 dB/mm and by 26.0 dB/octave. The inhibition was symmetrical for the masker placed basal to the probe (base‐to‐apex) and the masker placed apical to the probe (apex‐to‐base). Conclusion The interaction between neighboring optical sources during infrared laser stimulation is less than the interaction between neighboring electrical contacts during electrical stimulation. Previously published data for electrical stimulation reported an average current spread in human and cat cochleae of 2.8 dB/mm. With the increased number of independent channels for optical stimulation, it is anticipated that speech and music performance will improve. Lasers Surg. Med. © 2020 Wiley Periodicals LLC

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Section: Discussionmentioning

confidence: 99%

Channel Interaction During Infrared Light Stimulation in the Cochlea

Agarwal

Tan

et al. 2021

Lasers Surg Med

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“…The ongoing debate is if the resulting pressure is the dominating effect in cochlear INS. Results have been presented where cochlear INS did not evoke responses in deaf animals, 60‐64 and yet results from experiments in genetically manipulated mice with missing or non‐functional hair cells (Figure 1), and a study in deaf white cats argue for a direct stimulation of spiral ganglion neurons during INS 8,65,66 . The negative studies also differ from experiments where INS evokes auditory brainstem responses (ABRs) in congenitally deaf mice such as Atoh1 f/kiNeurog1 mice, which showed no ABR response to acoustical stimuli 65,67,68 .…”

Section: Introductionmentioning

confidence: 95%

Near‐infrared stimulation of the auditory nerve: A decade of progress toward an optical cochlear implant

Littlefield

Richter

2021

Laryngoscope Investig Oto

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Objectives We provide an appraisal of recent research on stimulation of the auditory system with light. In particular, we discuss direct infrared stimulation and ongoing controversies regarding the feasibility of this modality. We also discuss advancements and barriers to the development of an optical cochlear implant. Methods This is a review article that covers relevant animal studies. Results The auditory system has been stimulated with infrared light, and in a much more spatially selective manner than with electrical stimulation. However, there are experiments from other labs that have not been able to reproduce these results. This has resulted in an ongoing controversy regarding the feasibility of infrared stimulation, and the reasons for these experimental differences still require explanation. The neural response characteristics also appear to be much different than with electrical stimulation. The electrical stimulation paradigms used for modern cochlear implants do not apply well to optical stimulation and new coding strategies are under development. Stimulation with infrared light brings the risk of heat accumulation in the tissue at high pulse repetition rates, so optimal pulse shapes and combined optical/electrical stimulation are being investigated to mitigate this. Optogenetics is another promising technique, which makes neurons more sensitive to light stimulation by inserting light sensitive ion channels via viral vectors. Challenges of optogenetics include the expression of light sensitive channels in sufficient density in the target neurons, and the risk of damaging neurons by the expression of a foreign protein. Conclusion Optical stimulation of the nervous system is a promising new field, and there has been progress toward the development of a cochlear implant that takes advantage of the benefits of optical stimulation. There are barriers, and controversies, but so far none that seem intractable. Level of evidence NA (animal studies and basic research).

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“…Optical stimulation of the cochlea got started by Richter and colleagues, who have used pulsed infrared lasers to stimulate SGNs (Izzo et al, 2007). However, these experiments revealed a high-energy threshold for neural activation (starting at 15 lJ per pulse; Izzo et al, 2007;Tan et al, 2015) and the utility of direct infrared stimulation of SGNs has been challenged by studies in other laboratories (Teudt et al, 2011;Thompson et al, 2015;Kallweit et al, 2016;Baumhoff et al, 2019). Lower light requirements as compared to infrared neural stimulation and a molecularly defined mechanism of neural activation by light are offered by optogenetics: One and a half decades ago, it has been demonstrated that light-gated ion channels found in green algae, called Channelrhodopsins (ChRs; a subtype of microbial opsins), mediate light-driven action potentials in mammalian neurons (Nagel et al, 2003;Boyden et al, 2005).…”

Section: Vector Strengthmentioning

confidence: 99%

“…Optical stimulation of the cochlea got started by Richter and colleagues, who have used pulsed infrared lasers to stimulate SGNs (Izzo et al , ). However, these experiments revealed a high‐energy threshold for neural activation (starting at 15 μJ per pulse; Izzo et al , ; Tan et al , ) and the utility of direct infrared stimulation of SGNs has been challenged by studies in other laboratories (Teudt et al , ; Thompson et al , ; Kallweit et al , ; Baumhoff et al , ).…”

Section: A Primer To Acoustic Electric and Optogenetic Hearingmentioning

confidence: 99%

Towards the optical cochlear implant: optogenetic approaches for hearing restoration

2020

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Cochlear implants (CIs) are considered the most successful neuroprosthesis as they enable speech comprehension in the majority of half a million CI users suffering from sensorineural hearing loss. By electrically stimulating the auditory nerve, CIs constitute an interface re‐connecting the brain and the auditory scene, providing the patient with information regarding the latter. However, since electric current is hard to focus in conductive environments such as the cochlea, the precision of electrical sound encoding—and thus quality of artificial hearing—is limited. Recently, optogenetic stimulation of the cochlea has been suggested as an alternative approach for hearing restoration. Cochlear optogenetics promises increased spectral selectivity of artificial sound encoding, hence improved hearing, as light can conveniently be confined in space to activate the auditory nerve within smaller tonotopic ranges. In this review, we discuss the latest experimental and technological developments of cochlear optogenetics and outline the remaining challenges on the way to clinical translation.

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Intracochlear near infrared stimulation: Feasibility of optoacoustic stimulation in vivo

Cited by 27 publications

References 36 publications

Channel Interaction During Infrared Light Stimulation in the Cochlea

Channel Interaction During Infrared Light Stimulation in the Cochlea

Near‐infrared stimulation of the auditory nerve: A decade of progress toward an optical cochlear implant

Towards the optical cochlear implant: optogenetic approaches for hearing restoration

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