Optical cochlear implants: Evaluation of surgical approach and laser parameters in cats (original) (raw)
Related papers
Infrared neural stimulation: Beam path in the guinea pig cochlea
Hearing Research, 2011
It has been demonstrated INS can be utilized to stimulate spiral ganglion cells in the cochlea. Although neural stimulation can be achieved without direct contact of the radiation source and the tissue, the presence of fluids or bone between the target structure and the radiation source may lead to absorption or scattering of the radiation, which may limit the efficacy of INS. The present study demonstrates the neural structures in the radiation beam path that can be stimulated. Histological reconstructions and microCT of guinea pig cochleae stimulated with an infrared laser suggest that the orientation of the beam from the optical fiber determined the site of stimulation in the cochlea. Best frequencies of the INS-evoked neural responses obtained from the central nucleus of the inferior colliculus matched the histological sites in the spiral ganglion.
Infrared neural stimulation in the cochlea
SPIE Proceedings, 2013
The application of photonics to manipulate and stimulate neurons and to study neural networks has gained momentum over the last decade. Two general methods have been used: the genetic expression of light or temperature sensitive ion channels in the plasma membrane of neurons (Optogenetics and Thermogenetics) and the direct stimulation of neurons using infrared radiation (Infrared Neural Stimulation, INS). Both approaches have their strengths and challenges, which are well understood with a profound understanding of the light tissue interaction(s). This paper compares the opportunities of the methods for the use in cochlear prostheses. Ample data are already available on the stimulation of the cochlea with INS. The data show that the stimulation is selective, feasible at rates that would be sufficient to encode acoustic information and may be beneficial over conventional pulsed electrical stimulation. A third approach, using lasers in stress confinement to generate pressure waves and to stimulate the functional cochlea mechanically will also be discussed.
Laser stimulation of the auditory nerve
Lasers in Surgery and Medicine, 2006
Background and ObjectivesFor centuries, electric current has been used to stimulate neurons. Shortcomings of electrical stimulation include the contact between the stimulating electrode and the tissue, and the non-selective stimulation of the tissue. In contrast to electric stimulation, optical radiation can provide spatially selective neural stimulation without tissue contact.For centuries, electric current has been used to stimulate neurons. Shortcomings of electrical stimulation include the contact between the stimulating electrode and the tissue, and the non-selective stimulation of the tissue. In contrast to electric stimulation, optical radiation can provide spatially selective neural stimulation without tissue contact.Study Design/Materials and MethodsAcute in vivo experiments using gerbils were conducted to record optically evoked compound action potentials (CAPs) from the cochlea.Acute in vivo experiments using gerbils were conducted to record optically evoked compound action potentials (CAPs) from the cochlea.ResultsOptical radiation evokes CAPs in normal hearing animals and in deafened animals, in which cochleae lack outer and inner hair cells. Stimulation threshold was measured as 0.018±0.003 J/cm2 (mean±SE). Laser radiation could be increased by 30–40 dB until drastic changes were seen in cochlear function. Cochlear response amplitudes to optical radiation were stable over extended stimulation times.Optical radiation evokes CAPs in normal hearing animals and in deafened animals, in which cochleae lack outer and inner hair cells. Stimulation threshold was measured as 0.018±0.003 J/cm2 (mean±SE). Laser radiation could be increased by 30–40 dB until drastic changes were seen in cochlear function. Cochlear response amplitudes to optical radiation were stable over extended stimulation times.ConclusionsWe have demonstrated that the auditory nerve can be stimulated by optical radiation. One potential clinical use of this technology would be for cochlear implants. Lasers Surg. Med. 38:745–753, 2006. © 2006 Wiley-Liss, Inc.We have demonstrated that the auditory nerve can be stimulated by optical radiation. One potential clinical use of this technology would be for cochlear implants. Lasers Surg. Med. 38:745–753, 2006. © 2006 Wiley-Liss, Inc.
Laser Stimulation of Auditory Neurons: Effect of Shorter Pulse Duration and Penetration Depth
Biophysical Journal, 2008
We have pioneered what we believe is a novel method of stimulating cochlear neurons, using pulsed infrared radiation, based on the hypothesis that optical radiation can provide more spatially selective stimulation of the cochlea than electric current. Very little of the available optical parameter space has been used for optical stimulation of neurons. Here, we use a pulsed diode laser (1.94 mm) to stimulate auditory neurons of the gerbil. Radiant exposures measured at CAP threshold are similar for pulse durations of 5, 10, 30, and 100 ms, but greater for 300-ms-long pulses. There is evidence that water absorption of optical radiation is a significant factor in optical stimulation. Heat-transfer-based analysis of the data indicates that potential structures involved in optical stimulation of cochlear neurons have a dimension on the order of ;10 mm. The implications of these data could direct further research and design of an optical cochlear implant.
Laser stimulation of single auditory nerve fibers
The Laryngoscope, 2010
Objectives/Hypothesis-One limitation with cochlear implants is the difficulty stimulating spatially discrete spiral ganglion cell groups because of electrode interactions. Multipolar electrodes have improved on this some, but also at the cost of much higher device power consumption. Recently, it has been shown that spatially selective stimulation of the auditory nerve is possible with a mid-infrared laser aimed at the spiral ganglion via the round window. However, these neurons must be driven at adequate rates for optical radiation to be useful in cochlear implants. We herein use single-fiber recordings to characterize the responses of auditory neurons to optical radiation. Study Design-In vivo study using normal-hearing adult gerbils. Methods-Two diode lasers were used for stimulation of the auditory nerve. They operated between 1.844 μm and 1.873 μm, with pulse durations of 35 μs to 1,000 μs, and at repetition rates up to 1,000 pulses per second (pps). The laser outputs were coupled to a 200-μm-diameter optical fiber placed against the round window membrane and oriented toward the spiral ganglion. The auditory nerve was exposed through a craniotomy, and recordings were taken from single fibers during acoustic and laser stimulation. Results-Action potentials occurred 2.5 ms to 4.0 ms after the laser pulse. The latency jitter was up to 3 ms. Maximum rates of discharge averaged 97 ± 52.5 action potentials per second. The neurons did not strictly respond to the laser at stimulation rates over 100 pps. Conclusions-Auditory neurons can be stimulated by a laser beam passing through the round window membrane and driven at rates sufficient for useful auditory information. Optical stimulation and electrical stimulation have different characteristics; which could be selectively exploited in future cochlear implants. Level of Evidence-Not applicable.
Auditory responses to electric and infrared neural stimulation of the rat cochlear nucleus
Hearing Research, 2014
In an effort to improve the auditory brainstem implant, a prosthesis in which user outcomes are modest, we applied electric and infrared neural stimulation (INS) to the cochlear nucleus in a rat animal model. Electric stimulation evoked regions of neural activation in the inferior colliculus and short-latency, multipeaked auditory brainstem responses (ABRs). Pulsed INS, delivered to the surface of the cochlear nucleus via an optical fiber, evoked broad neural activation in the inferior colliculus. Strongest responses were recorded when the fiber was placed at lateral positions on the cochlear nucleus, close to the temporal bone. INS-evoked ABRs were multipeaked but longer in latency than those for electric stimulation; they resembled the responses to acoustic stimulation. After deafening, responses to electric stimulation persisted, whereas those to INS disappeared, consistent with a reported "optophonic" effect, a laser-induced acoustic artifact. Thus, for deaf individuals who use the auditory brainstem implant, INS alone did not appear promising as a new approach.
Infrared neural stimulation fails to evoke neural activity in the deaf guinea pig cochlea
Hearing research, 2015
At present there is some debate as to the processes by which infrared neural stimulation (INS) activates neurons in the cochlea, as the lasers used for INS can potentially generate a range of secondary stimuli e.g. an acoustic stimulus is produced when the light is absorbed by water. To clarify whether INS in the cochlea requires functioning hair cells and to explore the potential relevance to cochlear implants, experiments using INS were performed in the cochleae of both normal hearing and profoundly deaf guinea pigs. A response to laser stimulation was readily evoked in normal hearing cochlea. However, no response was evoked in any profoundly deaf cochleae, for either acute or chronic deafening, contrary to previous work where a response was observed after acute deafening with ototoxic drugs. A neural response to electrical stimulation was readily evoked in all cochleae after deafening. The absence of a response from optical stimuli in profoundly deaf cochleae suggests that the re...
Stimulation of the human auditory nerve with optical radiation
2009
A novel, spatially selective method to stimulate cranial nerves has been proposed: contact free stimulation with optical radiation. The radiation source is an infrared pulsed laser. The Case Report is the first report ever that shows that optical stimulation of the auditory nerve is possible in the human. The ethical approach to conduct any measurements or tests in humans requires efficacy and safety studies in animals, which have been conducted in gerbils. This report represents the first step in a translational research project to initiate a paradigm shift in neural interfaces. A patient was selected who required surgical removal of a large meningioma angiomatum WHO I by a planned transcochlear approach. Prior to cochlear ablation by drilling and subsequent tumor resection, the cochlear nerve was stimulated with a pulsed infrared laser at low radiation energies. Stimulation with optical radiation evoked compound action potentials from the human auditory nerve. Stimulation of the auditory nerve with infrared laser pulses is possible in the human inner ear. The finding is an important step for translating results from animal experiments to human and furthers the development of a novel interface that uses optical radiation to stimulate neurons. Additional measurements are required to optimize the stimulation parameters.
Target structures for cochlear infrared neural stimulation
Neurophotonics, 2015
Infrared neural stimulation (INS) is a method to depolarize neurons with infrared light. While consensus exists that heating of the target structure is essential, subsequent steps that result in the generation of an action potential are controversially discussed in the literature. The question of whether cochlear INS is an acoustic event has not been clarified. Results have been published that could be explained solely by an acoustic event. However, data exist that do not support an acoustical stimulus as the dominant factor in cochlear INS. We review the different findings that have been suggested for the mechanism of INS. Furthermore, we present the data that clarify the role of an acoustical event in cochlear INS. Masking experiments have been performed in hearing, hearing impaired, and severely hearing impaired animals. In normal hearing animals, the laser response could be masked by the acoustic stimulus. Once thresholds to acoustic stimuli were elevated, the ability to acoustically mask the INS response gradually disappeared. Thresholds for acoustic stimuli were significantly elevated in animals with compromised cochlear function, while the thresholds for optical stimulation remained largely unchanged. The results suggest that the direct interaction between the radiation and the target structure dominates cochlear INS.
Journal of Neurosurgery, 2001
INCE 1979, when the pioneering work of William House and colleagues lead to the development of the first ABI, ,31 more than 180 profoundly deaf patients with neurofibromatosis Type II have received such a prosthesis for partial restoration of hearing. The surgical procedure is well established for both the suboccipital and the translabyrinthine approach. Speech processing strategies, originally adapted from cochlear implantation, have been refined, and the number of channels on electrode carriers has been increased to more than 20 in some of these devices; 15 however, the quality of hearing perception afforded by the ABI still does not significantly exceed that of a dual-channel cochlear implant.