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Littlefield PD, Richter C. Near-infrared stimulation of the auditory nerve: A decade of progress toward an optical cochlear implant. Laryngoscope Investig Otolaryngol 2021; 6:310-319. [PMID: 33869763 PMCID: PMC8035937 DOI: 10.1002/lio2.541] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2020] [Revised: 12/14/2020] [Accepted: 02/12/2021] [Indexed: 12/21/2022] Open
Abstract
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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Affiliation(s)
| | - Claus‐Peter Richter
- Department of OtolaryngologyNorthwestern UniversityChicagoIllinoisUSA
- Department of Communication Sciences and DisordersNorthwestern UniversityEvanstonIllinoisUSA
- Department of Biomedical EngineeringNorthwestern UniversityEvanstonIllinoisUSA
- The Hugh Knowles Center, Department of Communication Sciences and DisordersNorthwestern UniversityEvanstonIllinoisUSA
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Xu Y, Xia N, Lim M, Tan X, Tran MH, Boulger E, Peng F, Young H, Rau C, Rack A, Richter CP. Multichannel optrodes for photonic stimulation. NEUROPHOTONICS 2018; 5:045002. [PMID: 30397630 PMCID: PMC6197865 DOI: 10.1117/1.nph.5.4.045002] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/16/2018] [Accepted: 09/24/2018] [Indexed: 05/27/2023]
Abstract
An emerging method in the field of neural stimulation is the use of photons to activate neurons. The possible advantage of optical stimulation over electrical is attributable to its spatially selective activation of small neuron populations, which is promising in generating superior spatial resolution in neural interfaces. Two principal methods are explored for cochlear prostheses: direct stimulation of nerves with infrared light and optogenetics. This paper discusses basic requirements for developing a light delivery system (LDS) for the cochlea and provides examples for building such devices. The proposed device relies on small optical sources, which are assembled in an array to be inserted into the cochlea. The mechanical properties, the biocompatibility, and the efficacy of optrodes have been tested in animal models. The force required to insert optrodes into a model of the human scala tympani was comparable to insertion forces obtained for contemporary cochlear implant electrodes. Side-emitting diodes are powerful enough to evoke auditory responses in guinea pigs. Chronic implantation of the LDS did not elevate auditory brainstem responses over 26 weeks.
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Affiliation(s)
- Yingyue Xu
- Northwestern University Feinberg School of Medicine, Department of Otolaryngology, Chicago, Illinois, United States
- Northwestern University, Department of Communication Sciences and Disorders, Evanston, Illinois, United States
| | - Nan Xia
- Qingdao University, Institute for Digital Medicine and Computer-assisted Surgery, Qingdao, China
| | - Michelle Lim
- Northwestern University Feinberg School of Medicine, Department of Otolaryngology, Chicago, Illinois, United States
| | - Xiaodong Tan
- Northwestern University Feinberg School of Medicine, Department of Otolaryngology, Chicago, Illinois, United States
| | - Minh Ha Tran
- Northwestern University Feinberg School of Medicine, Department of Otolaryngology, Chicago, Illinois, United States
| | - Erin Boulger
- Northwestern University Feinberg School of Medicine, Department of Otolaryngology, Chicago, Illinois, United States
| | - Fei Peng
- Chongqing University, Bioengineering College, Chongqing, China
| | - Hunter Young
- Northwestern University Feinberg School of Medicine, Department of Otolaryngology, Chicago, Illinois, United States
| | - Christoph Rau
- Diamond Light Source Ltd., Diamond House, Harwell Science and Innovation Campus, Didcot, Oxfordshire, United Kingdom
| | - Alexander Rack
- Structure of Materials Group-ID19, European Synchrotron Radiation Facility, Cedex 9, France
| | - Claus-Peter Richter
- Northwestern University Feinberg School of Medicine, Department of Otolaryngology, Chicago, Illinois, United States
- Northwestern University, Department of Communication Sciences and Disorders, Evanston, Illinois, United States
- Northwestern University, Department of Biomedical Engineering, Evanston, Illinois, United States
- Northwestern University, Hugh Knowles Center for Clinical and Basic Sciences in Hearing, Evanston, Illinois, United States
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