Virtual Rhesus Labyrinth Model Predicts Responses to Electrical Stimulation Delivered by a Vestibular Prosthesis

Hedjoudje, Abderrahmane; Hayden, Russell; Dai, Chenkai; Ahn, Joong Ho; Rahman, Mehdi A.; Risi, Frank; Zhang, Jiangyang; Mori, Susumu; Santina, Charles C. Della

doi:10.1007/s10162-019-00725-3

Cited by 16 publications

(20 citation statements)

References 79 publications

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“…For example, electrode contact locations can be used as input to individualized finite element models that, once adequately validated via comparison with real data, can facilitate interpretation of empiric data, generation of testable hypotheses, and optimization of electrode array designs through simulation. 12 In the present study, we found that the locations of stimulating electrodes and their relation to vestibular bony structures can be depicted precisely with FPCT. All stimulating electrode arrays were close to their target end organs within the target ampullae; however, they varied with respect to location: adjacent to or far from the bone walls of each ampulla.…”

Section: Discussionsupporting

confidence: 62%

“…Typically, 1 electrode on an electrode array of a given canal outperforms the others that are 250-500 um away. 12 Knowing vestibular implant array location, their insertion depth, and distance from target vestibular nerve branches can provide helpful information to choose the best electrodes to activate and define stimulus parameters to use, valuable insights that can drive iterative improvements in electrode array design and surgical technique. For example, electrode contact locations can be used as input to individualized finite element models that, once adequately validated via comparison with real data, can facilitate interpretation of empiric data, generation of testable hypotheses, and optimization of electrode array designs through simulation.…”

Section: Discussionmentioning

confidence: 99%

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Vestibular Implant Imaging

Hedjoudje

Schoo²,

Ward³

et al. 2020

AJNR Am J Neuroradiol

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Analogous to hearing restoration via cochlear implants, vestibular function could be restored via vestibular implants that electrically stimulate vestibular nerve branches to encode head motion. This study presents the technical feasibility and first imaging results of CT for vestibular implants in 8 participants of the first-in-human Multichannel Vestibular Implant Early Feasibility Study. Imaging characteristics of 8 participants (3 men, 5 women; median age, 59.5 years; range, 51-66 years) implanted with a Multichannel Vestibular Implant System who underwent a postimplantation multislice CT (n ¼ 2) or flat panel CT (n ¼ 6) are reported. The device comprises 9 platinum electrodes inserted into the ampullae of the 3 semicircular canals and 1 reference electrode inserted in the common crus. Electrode insertion site, positions, length and angle of insertion, and number of artifacts were assessed. Individual electrode contacts were barely discernible in the 2 participants imaged using multislice CT. Electrode and osseous structures were detectable but blurred so that only 12 of the 18 stimulating electrode contacts could be individually identified. Flat panel CT could identify all 10 electrode contacts in all 6 participants. The median reference electrode insertion depth angle was 9°(range, À57.5°to 45°), and the median reference electrode insertion length was 42 mm (range, À21À66 mm). Flat panel CT of vestibular implants produces higher-resolution images with fewer artifacts than multidetector row CT, allowing visualization of individual electrode contacts and quantification of their locations relative to vestibular semicircular canals and ampullae. As multichannel vestibular implant imaging improves, so will our understanding of the relationship between electrode placement and vestibular performance.

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Section: Discussionsupporting

confidence: 62%

Section: Discussionmentioning

confidence: 99%

Vestibular Implant Imaging

Hedjoudje

Schoo²,

Ward³

et al. 2020

AJNR Am J Neuroradiol

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“…Comparable variability in evoked VOR gains has likewise been reported across subjects in prior human [ 15 , 21 ] and monkey [ 16 , 34 ] studies. One factor that could contribute to such gain variability is differences in the precise placement of the electrodes targeting the ampullae [ 52 ]. Indeed, optimization of electrode placement is a focus of ongoing research [ 53 , 54 ].…”

Section: Discussionmentioning

confidence: 99%

A prosthesis utilizing natural vestibular encoding strategies improves sensorimotor performance in monkeys

et al. 2022

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Sensory pathways provide complex and multifaceted information to the brain. Recent advances have created new opportunities for applying our understanding of the brain to sensory prothesis development. Yet complex sensor physiology, limited numbers of electrodes, and nonspecific stimulation have proven to be a challenge for many sensory systems. In contrast, the vestibular system is uniquely suited for prosthesis development. Its peripheral anatomy allows site-specific stimulation of 3 separate sensory organs that encode distinct directions of head motion. Accordingly, here, we investigated whether implementing natural encoding strategies improves vestibular prosthesis performance. The eye movements produced by the vestibulo-ocular reflex (VOR), which plays an essential role in maintaining visual stability, were measured to quantify performance. Overall, implementing the natural tuning dynamics of vestibular afferents produced more temporally accurate VOR eye movements. Exploration of the parameter space further revealed that more dynamic tunings were not beneficial due to saturation and unnatural phase advances. Trends were comparable for stimulation encoding virtual versus physical head rotations, with gains enhanced in the latter case. Finally, using computational methods, we found that the same simple model explained the eye movements evoked by sinusoidal and transient stimulation and that a stimulation efficacy substantially less than 100% could account for our results. Taken together, our results establish that prosthesis encodings that incorporate naturalistic afferent dynamics and account for activation efficacy are well suited for restoration of gaze stability. More generally, these results emphasize the benefits of leveraging the brain’s endogenous coding strategies in prosthesis development to improve functional outcomes.

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“…The assumption of quasi-static conditions using purely resistive components without considering time and frequency-dependency of the tissue conductivity or reactance was employed in all the above-mentioned computer models. This simplification was claimed to be justified because dielectric relaxation times in cochlear tissues were shorter than the time scale of the applied stimuli, and 95 % of the spectral energy of the tested stimulus waveforms was below 12.5 kHz [ 13 , 15 , 17 ]. On the other hand, it has been shown in literature that the quasi-static approximation is only valid if [ 18 ]: / 1.…”

Section: Introductionmentioning

confidence: 99%

Computer Simulation of the Electrical Stimulation of the Human Vestibular System: Effects of the Reactive Component of Impedance on Voltage Waveform and Nerve Selectivity

D'Alessandro

Handler

Saba

et al. 2022

JARO

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The vestibular system is responsible for our sense of balance and spatial orientation. Recent studies have shown the possibility of partially restoring the function of this system using vestibular implants. Electrical modeling is a valuable tool in assisting the development of these implants by analyzing stimulation effects. However, previous modeling approaches of the vestibular system assumed quasi-static conditions. In this work, an extended modeling approach is presented that considers the reactive component of impedance and the electrode-tissue interface and their effects are investigated in a 3D human vestibular computer model. The Fourier finite element method was employed considering the frequency-dependent electrical properties of the different tissues. The electrode-tissue interface was integrated by an instrumental electrode model. A neuron model of myelinated fibers was employed to predict the nerve responses to the electrical stimulus. Morphological changes of the predicted voltage waveforms considering the dielectric tissue properties were found compared to quasi-static simulations, particularly during monopolar electrode configuration. Introducing the polarization capacitance and the scar tissue around the electrode in combination with a power limitation leads to a considerable current reduction applied through the active electrode and, consequently, to reduced voltage amplitudes of the stimulus waveforms. The reactive component of impedance resulted in better selectivity for the excitation of target nerves compared to the quasi-static simulation at the expense of slightly increased stimulus current amplitudes. We conclude that tissue permittivity and effects of the electrode-tissue interface should be considered to improve the accuracy of the simulations.

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Virtual Rhesus Labyrinth Model Predicts Responses to Electrical Stimulation Delivered by a Vestibular Prosthesis

Cited by 16 publications

References 79 publications

Vestibular Implant Imaging

Vestibular Implant Imaging

A prosthesis utilizing natural vestibular encoding strategies improves sensorimotor performance in monkeys

Computer Simulation of the Electrical Stimulation of the Human Vestibular System: Effects of the Reactive Component of Impedance on Voltage Waveform and Nerve Selectivity

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