scholarly journals Polarity Sensitivity in Pediatric and Adult Cochlear Implant Listeners

2019 ◽  
Vol 23 ◽  
pp. 233121651986298 ◽  
Author(s):  
Kelly N. Jahn ◽  
Julie G. Arenberg
Keyword(s):  
Cochlear Implant ◽  
Dynamic Range ◽  
Single Channel ◽  
Spiral Ganglion ◽  
High Amplitude ◽  
Electrical Stimulus ◽  
Polarity Sensitivity ◽  
The Difference ◽  
Phoneme Perception ◽  
Ganglion Neurons

Modeling data suggest that sensitivity to the polarity of an electrical stimulus may reflect the integrity of the peripheral processes of the spiral ganglion neurons. Specifically, better sensitivity to anodic (positive) current than to cathodic (negative) current could indicate peripheral process degeneration or demyelination. The goal of this study was to characterize polarity sensitivity in pediatric and adult cochlear implant listeners (41 ears). Relationships between polarity sensitivity at threshold and (a) polarity sensitivity at suprathreshold levels, (b) age-group, (c) preimplantation duration of deafness, and (d) phoneme perception were determined. Polarity sensitivity at threshold was defined as the difference in single-channel behavioral thresholds measured in response to each of two triphasic pulses, where the central high-amplitude phase was either cathodic or anodic. Lower thresholds in response to anodic than to cathodic pulses may suggest peripheral process degeneration. On the majority of electrodes tested, threshold and suprathreshold sensitivity was lower for anodic than for cathodic stimulation; however, dynamic range was often larger for cathodic than for anodic stimulation. Polarity sensitivity did not differ between child- and adult-implanted listeners. Adults with long preimplantation durations of deafness tended to have better sensitivity to anodic pulses on channels that were estimated to interface poorly with the auditory nerve; this was not observed in the child-implanted group. Across subjects, duration of deafness predicted phoneme perception performance. The results of this study suggest that subject- and electrode-dependent differences in polarity sensitivity may assist in developing customized cochlear implant programming interventions for child- and adult-implanted listeners.

scholarly journals Neural Tissue Degeneration in Rosenthal’s Canal and Its Impact on Electrical Stimulation of the Auditory Nerve by Cochlear Implants: An Image-Based Modeling Study

2020 ◽  
Vol 21 (22) ◽  
pp. 8511
Author(s):  
Kiran Kumar Sriperumbudur ◽  
Revathi Appali ◽  
Anthony W. Gummer ◽  
Ursula van Rienen
Keyword(s):  
Cochlear Implant ◽  
Cochlear Implants ◽  
Auditory Nerve ◽  
Ganglion Cells ◽  
Spiral Ganglion ◽  
Sensorineural Deafness ◽  
Neural Tissue ◽  
Neural Degeneration ◽  
Tissue Degeneration ◽  
Ganglion Neurons

Sensorineural deafness is caused by the loss of peripheral neural input to the auditory nerve, which may result from peripheral neural degeneration and/or a loss of inner hair cells. Provided spiral ganglion cells and their central processes are patent, cochlear implants can be used to electrically stimulate the auditory nerve to facilitate hearing in the deaf or severely hard-of-hearing. Neural degeneration is a crucial impediment to the functional success of a cochlear implant. The present, first-of-its-kind two-dimensional finite-element model investigates how the depletion of neural tissues might alter the electrically induced transmembrane potential of spiral ganglion neurons. The study suggests that even as little as 10% of neural tissue degeneration could lead to a disproportionate change in the stimulation profile of the auditory nerve. This result implies that apart from encapsulation layer formation around the cochlear implant electrode, tissue degeneration could also be an essential reason for the apparent inconsistencies in the functionality of cochlear implants.

scholarly journals Hair cells use active zones with different voltage dependence of Ca2+ influx to decompose sounds into complementary neural codes

2016 ◽  
Vol 113 (32) ◽  
pp. E4716-E4725 ◽  
Author(s):  
Tzu-Lun Ohn ◽  
Mark A. Rutherford ◽  
Zhizi Jing ◽  
Sangyong Jung ◽  
Carlos J. Duque-Afonso ◽  
...  
Keyword(s):  
Hair Cells ◽  
Dynamic Range ◽  
Spiral Ganglion ◽  
Spatial Gradient ◽  
Auditory Information ◽  
Neural Codes ◽  
Deafness Gene ◽  
Wide Range ◽  
Ganglion Neurons ◽  
Channel Properties

For sounds of a given frequency, spiral ganglion neurons (SGNs) with different thresholds and dynamic ranges collectively encode the wide range of audible sound pressures. Heterogeneity of synapses between inner hair cells (IHCs) and SGNs is an attractive candidate mechanism for generating complementary neural codes covering the entire dynamic range. Here, we quantified active zone (AZ) properties as a function of AZ position within mouse IHCs by combining patch clamp and imaging of presynaptic Ca2+ influx and by immunohistochemistry. We report substantial AZ heterogeneity whereby the voltage of half-maximal activation of Ca2+ influx ranged over ∼20 mV. Ca2+ influx at AZs facing away from the ganglion activated at weaker depolarizations. Estimates of AZ size and Ca2+ channel number were correlated and larger when AZs faced the ganglion. Disruption of the deafness gene GIPC3 in mice shifted the activation of presynaptic Ca2+ influx to more hyperpolarized potentials and increased the spontaneous SGN discharge. Moreover, Gipc3 disruption enhanced Ca2+ influx and exocytosis in IHCs, reversed the spatial gradient of maximal Ca2+ influx in IHCs, and increased the maximal firing rate of SGNs at sound onset. We propose that IHCs diversify Ca2+ channel properties among AZs and thereby contribute to decomposing auditory information into complementary representations in SGNs.

scholarly journals Cochlear-Bioelectrode: Auditory response to cochlear implant can be improved by stem cell delivery into inner ear in a pig model

2021 ◽  
Author(s):  
Shiming Yang ◽  
Wei Chen
Keyword(s):  
Stem Cell ◽  
Cochlear Implant ◽  
Fluorescent Protein ◽  
Dynamic Range ◽  
Pig Model ◽  
Auditory Brainstem Responses ◽  
Cell Delivery ◽  
Swine Model ◽  
Stem Cell Delivery ◽  
Ganglion Neurons

Abstract Cochlear implant (CI) is the most successful auditory prosthesis and has changed the life for nearly half million people with profound hearing loss. The number and function of spiral ganglion neurons (SGNs) in the cochlea are crucial to CI performance. Clinically, some patients with SGNs degeneration fail to return to normal life due to unsatisfactory performance of their CIs. In this study, we show in a swine model that combined stem cell delivery and electrical stimulation (ES) via CI (defined as Cochlear-Bioelectrode) achieved stem cell enrichment near the SGNs and lowered CI stimulation thresholds. ES generated by the cochlear implant electrode array guided human induced pluripotent stem cells (hiPSCs) with a green fluorescent protein (GFP) marker to cross the osseous spiral lamina via naturally existing openings and congregate in the SGN region. In seven days, surprisingly efficient hiPSC migration into the SGN region was demonstrated, while hiPSC delivery and enrichment in the SGN region failed without ES. After two weeks of combined electric stimulation and stem cell delivery treatment, the number of SGNs increased significantly in the 60-day old pig model (mean number = 129.6/field), as compared to untreated deafness pigs of the same age (mean number = 6.2/field). With the replenished SGNs, CI stimulation thresholds were significantly reduced and hearing sensitivity and dynamic range extended, as demonstrated by electrically evoked auditory brainstem responses. Our findings provide the first evidence that in vivo Cochlear-Bioelectrode (CBe) may be feasible with broad promising clinical applications.

scholarly journals The Influence of Cochlear Implant-Based Electric Stimulation on the Electrophysiological Characteristics of Cultured Spiral Ganglion Neurons

2020 ◽  
Vol 2020 ◽  
pp. 1-8
Author(s):  
Na Shen ◽  
Lei Zhou ◽  
Bin Lai ◽  
Shufeng Li
Keyword(s):  
Electrical Stimulation ◽  
Cochlear Implant ◽  
Spiral Ganglion ◽  
Reversal Potential ◽  
Neurite Growth ◽  
Spiral Ganglion Neuron ◽  
Spiral Ganglion Neurons ◽  
Vitro Model ◽  
Ganglion Neurons

Background. Cochlear implant-based electrical stimulation may be an important reason to induce the residual hearing loss after cochlear implantation. In our previous study, we found that charge-balanced biphasic electrical stimulation inhibited the neurite growth of spiral ganglion neurons (SGNs) and decreased Schwann cell density in vitro. In this study, we want to know whether cochlear implant-based electrical stimulation can induce the change of electrical activity in cultured SGNs. Methods. Spiral ganglion neuron electrical stimulation in vitro model is established using the devices delivering cochlear implant-based electrical stimulation. After 48 h treatment by 50 μA or 100 μA electrical stimulation, the action potential (AP) and voltage depended calcium current (ICa) of SGNs are recorded using whole-cell electrophysiological method. Results. The results show that the ICa of SGNs is decreased significantly in 50 μA and 100 μA electrical stimulation groups. The reversal potential of ICa is nearly +80 mV in control SGN, but the reversal potential decreases to +50 mV in 50 μA and 100 μA electrical stimulation groups. Interestingly, the AP amplitude, the AP latency, and the AP duration of SGNs have no statistically significant differences in all three groups. Conclusion. Our study suggests cochlear implant-based electrical stimulation only significantly inhibit the ICa of cultured SGNs but has no effect on the firing of AP, and the relation of ICa inhibition and SGN damage induced by electrical stimulation and its mechanism needs to be further studied.

scholarly journals Comparison of Place-versus-Pitch Mismatch between a Perimodiolar and Lateral Wall Cochlear Implant Electrode Array in Patients with Single-Sided Deafness and a Cochlear Implant

2019 ◽  
Vol 24 (1) ◽  
pp. 38-48 ◽  
Author(s):  
Jeroen P.M. Peters ◽  
Edwin Bennink ◽  
Gijsbert A. van Zanten
Keyword(s):  
Cochlear Implant ◽  
Spiral Ganglion ◽  
Electrode Array ◽  
Lateral Wall ◽  
Electrode Arrays ◽  
High Resolution Computed Tomography ◽  
Significant Difference ◽  
Electrode Contact ◽  
The Difference ◽  
Single Sided Deafness

Background: In electric-acoustic pitch matching experiments in patients with single-sided deafness and a cochlear implant, the observed “mismatch” between perceived pitch and predicted pitch, based on the amended Greenwood frequency map, ranges from –1 to –2 octaves. It is unknown if and how this mismatch differs for perimodiolar versus lateral wall electrode arrays. Objectives: We aimed to investigate if the type of electrode array design is of influence on the electric-acoustic pitch match. Method: Fourteen patients (n = 8 with CI422 + lateral wall electrode array, n = 6 with CI512 + perimodiolar electrode array; Cochlear Ltd.) compared the pitch of acoustic stimuli to the pitch of electric stimuli at two test sessions (average interval 4.3 months). We plotted these “pitch matches” per electrode contact against insertion angle, calculated from high-resolution computed tomography scans. The difference between these pitch matches and two references (the spiral ganglion map and the default frequency allocation by Cochlear Ltd.) was defined as “mismatch.” Results: We found average mismatches of –2.2 octaves for the CI422 group and –1.3 octaves for the CI512 group. For any given electrode contact, the mismatch was smaller for the CI512 electrode array than for the CI422 electrode array. For all electrode contacts together, there was a significant difference between the mismatches of the two groups (p < 0.05). Results remained stable over time, with no significant difference between the two test sessions considering all electrode contacts. Neither group showed a significant correlation between the mismatch and phoneme recognition scores. Conclusion: The pitch mismatch was smaller for the perimodiolar electrode array than for the lateral wall electrode array.

scholarly journals Evaluating and Comparing Behavioural and Electrophysiological Estimates of Neural Health in Cochlear Implant Users

2020 ◽  
Author(s):  
Tim Brochier ◽  
François Guérit ◽  
John M. Deeks ◽  
Charlotte Garcia ◽  
Manohar Bance ◽  
...  
Keyword(s):  
Spiral Ganglion ◽  
Electrode Array ◽  
Growth Function ◽  
Spiral Ganglion Neuron ◽  
Temporal Representation ◽  
Neuron Density ◽  
The Difference ◽  
Ganglion Neurons ◽  
Test Retest Reliability ◽  
Different Characteristics

Abstract Variations in neural health along the cochlea can degrade the spectral and temporal representation of sounds conveyed by cochlear implants (CIs). We evaluated and compared one electrophysiological measure and two behavioural measures that have been proposed as estimates of neural health patterns, in order to explore the extent to which the different measures provide converging and consistent neural health estimates. All measures were obtained from the same 11 users of the Cochlear Corporation CI. The two behavioural measures were multipulse integration (MPI) and the polarity effect (PE), both measured on each of seven electrodes per subject. MPI was measured as the difference between thresholds at 80 pps and 1000 pps, and PE as the difference in thresholds between cathodic- and anodic-centred quadraphasic (QP) 80-pps pulse trains. It has been proposed that good neural health corresponds to a large MPI and to a large negative PE (lower thresholds for cathodic than anodic pulses). The electrophysiological measure was the effect of interphase gap (IPG) on the offset of the ECAP amplitude growth function (AGF), which has been correlated with spiral ganglion neuron density in guinea pigs. This ‘IPG offset’ was obtained on the same subset of electrodes used for the behavioural measures. Despite high test–retest reliability, there were no significant correlations between the neural health estimates for either within-subject comparisons across the electrode array, or between-subject comparisons of the means. A phenomenological model of a population of spiral ganglion neurons was then used to investigate physiological mechanisms that might underlie the different neural health estimates. The combined experimental and modelling results provide evidence that PE, MPI and IPG offset may reflect different characteristics of the electrode-neural interface.

scholarly journals The Perception of Ramped Pulse Shapes in Cochlear Implant Users

2021 ◽  
Vol 25 ◽  
pp. 233121652110611
Author(s):  
Charlotte Amalie Navntoft ◽  
David M. Landsberger ◽  
Tania Rinaldi Barkat ◽  
Jeremy Marozeau
Keyword(s):  
Single Channel ◽  
Spiral Ganglion ◽  
Electrode Array ◽  
Neural Activation ◽  
Activation Patterns ◽  
Power Efficient ◽  
Threshold Detection ◽  
Electric Pulses ◽  
Significant Difference ◽  
Ganglion Neurons

The electric stimulation provided by current cochlear implants (CI) is not power efficient. One underlying problem is the poor efficiency by which information from electric pulses is transformed into auditory nerve responses. A novel stimulation paradigm using ramped pulse shapes has recently been proposed to remedy this inefficiency. The primary motivation is a better biophysical fit to spiral ganglion neurons with ramped pulses compared to the rectangular pulses used in most contemporary CIs. Here, we tested the hypotheses that ramped pulses provide more efficient stimulation compared to rectangular pulses and that a rising ramp is more efficient than a declining ramp. Rectangular, rising ramped and declining ramped pulse shapes were compared in terms of charge efficiency and discriminability, and threshold variability in seven CI listeners. The tasks included single-channel threshold detection, loudness-balancing, discrimination of pulse shapes, and threshold measurement across the electrode array. Results showed that reduced charge, but increased peak current amplitudes, was required at threshold and most comfortable levels with ramped pulses relative to rectangular pulses. Furthermore, only one subject could reliably discriminate between equally-loud ramped and rectangular pulses, suggesting variations in neural activation patterns between pulse shapes in that participant. No significant difference was found between rising and declining ramped pulses across all tests. In summary, the present findings show some benefits of charge efficiency with ramped pulses relative to rectangular pulses, that the direction of a ramped slope is of less importance, and that most participants could not perceive a difference between pulse shapes.

scholarly journals Evaluating and comparing behavioural and electrophysiological estimates of neural health in cochlear implant users

2020 ◽  
Author(s):  
Tim Brochier ◽  
Francois Guerit ◽  
Charlotte Garcia ◽  
John M. Deeks ◽  
Manohar L. Bance ◽  
...  
Keyword(s):  
Spiral Ganglion ◽  
Electrode Array ◽  
Growth Function ◽  
Physiological Mechanisms ◽  
Temporal Representation ◽  
Health Patterns ◽  
The Difference ◽  
Ganglion Neurons ◽  
Test Retest Reliability ◽  
Different Characteristics

Variations in neural health along the cochlea can degrade the spectral and temporal representation of sounds conveyed by cochlear implants (CIs) . We evaluated and compared several methods that have been proposed as estimates of neural health patterns, in order to explore the extent to which the different measures provide converging and consistent neural health estimates. All measures were obtained from the same 11 users of the Cochlear Corporation CI. The two behavioural measures were multipulse integration (MPI) and the polarity effect (PE), both measured on each of seven electrodes per subject. MPI was measured as the difference between thresholds at 80-pps and 1000-pps, and PE as the difference in thresholds between cathodic- and anodic-centred quadraphasic (QP) 80-pps pulse trains. It has been proposed that good neural health corresponds to a large MPI and to a large negative PE (lower thresholds for cathodic than anodic pulses). The electrophysiological measure was the effect of interphase gap (IPG) on the offset of the ECAP amplitude growth function (AGF), which has been correlated with spiral ganglion nerve density in guinea pigs. This “IPG offset” was obtained on the same subset of electrodes as for the behavioural measures. Despite high test-retest reliability, there were no significant correlations between the neural health estimates for either within-subject comparisons across the electrode array, or between-subjects comparisons of the means. A phenomenological model of a population of spiral ganglion neurons was then used to investigate physiological mechanisms that might underlie the different neural health estimates. The combined experimental and modelling results provide evidence that PE, MPI, and IPG offset reflect different characteristics of the electrode-neural interface.

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