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.

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 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 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 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.

Otopathologic Abnormalities in CHARGE Syndrome

2021 ◽  
pp. 019459982110089
Author(s):  
Rafael da Costa Monsanto ◽  
Renata Malimpensa Knoll ◽  
Norma de Oliveira Penido ◽  
Grace Song ◽  
Felipe Santos ◽  
...  
Keyword(s):  
Facial Nerve ◽  
Middle Ear ◽  
Spiral Ganglion ◽  
Internal Auditory Canal ◽  
Semicircular Canals ◽  
Charge Syndrome ◽  
University Of Minnesota ◽  
Bony Canal ◽  
Ganglion Neurons ◽  
Temporal Bones

Objective To perform an otopathologic analysis of temporal bones (TBs) with CHARGE syndrome. Study Design Otopathologic study of human TB specimens. Setting Otopathology laboratories. Methods From the otopathology laboratories at the University of Minnesota and Massachusetts Eye and Ear Infirmary, we selected TBs from donors with CHARGE syndrome. These TBs were serially sectioned at a thickness of 20 µm, and every 10th section was stained with hematoxylin and eosin. We performed otopathologic analyses of the external ear, middle ear (middle ear cleft, mucosal lining, ossicles, mastoid, and facial nerve), and inner ear (cochlea, vestibule, internal auditory canal, and cochlear and vestibular nerves). The gathered data were statistically analyzed. Results Our study included 12 TBs from 6 donors. We found a high prevalence of abnormalities affecting the ears. The most frequent findings were stapes malformation (100%), aberrant course of the facial nerve (100%) with narrow facial recess (50%), sclerotic and hypodeveloped mastoids (50%), cochlear (100%) and vestibular (83.3%) hypoplasia with aplasia of the semicircular canals, hypoplasia and aplasia of the cochlear (66.6%) and vestibular (91.6%) nerves, and narrowing of the bony canal of the cochlear nerve (66.6%). The number of spiral ganglion and Scarpa’s ganglion neurons were decreased in all specimens (versus normative data). Conclusions In our study, CHARGE syndrome was associated with multiple TB abnormalities that may severely affect audiovestibular function and rehabilitation.

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