Objective assessment of electrode discrimination with the auditory change complex in adult cochlear implant users

Mathew, Rajeev; Undurraga, Jaime A.; Li, Guoping; Meerton, Leah; Boyle, Patrick; Shaida, Azhar; Selvadurai, David; Jiang, Dan; Vickers, Deborah

doi:10.1016/j.heares.2017.07.008

Cited by 28 publications

(48 citation statements)

References 58 publications

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“…We recently showed that it is feasible to measure the spatial ACC in different types of CI devices and as early as 1-week after switch-on in adult CI users (Mathew et al, 2017). In addition, there was a strong relationship between objective and behavioural measures of electrode discrimination.…”

Section: A N U S C R I P Tmentioning

confidence: 99%

“…One participant dropped out of the study after the first recording session and was therefore excluded from the analysis. Of the remaining 10 participants, 9 had taken part in our previous study (Mathew et al 2017). All participants were unilaterally implanted with an Advanced Bionics (AB) Hi-Res 90K device with full electrode array insertion and normal electrode impedances.…”

Section: Participantsmentioning

confidence: 99%

“…Stimuli were as described in our previous study (Mathew et al, 2017). The participants own speech processor was bypassed and electrodes were stimulated with a platinum sound processor through a research interface (BEDCS version 1.18.288 from AB).…”

Section: Stimuli For Measuring Electrode Discriminationmentioning

confidence: 99%

“…The average of two measurements was used as the final MC level. In order to reduce loudness cues when switching the active electrode, electrode pairs were carefully loudness balanced as described previously (Mathew et al 2017). The stimulation level of the test electrode was initially set at the MC level of the reference electrode.…”

Section: Stimuli For Measuring Electrode Discriminationmentioning

confidence: 99%

“…Although electrode discrimination is a multimodal percept (Collins et al, 1997), it is thought to be predominantly a measure of spatial resolution. Electrode discrimination ability has been correlated with speech perception in adult and paediatric CI populations (Busby et al, 2000;Dawson et al, 2000;Mathew et al, 2017) and the results of electrode discrimination tests have been used to optimize the CI map in a number of studies (Saleh et al, 2013;Vickers et al, 2016;Zwolan et al, 1997). However, if such interventions are to be carried out, then it would be helpful to understand how these psychophysical abilities develop over time.…”

Section: Introductionmentioning

confidence: 99%

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Development of electrophysiological and behavioural measures of electrode discrimination in adult cochlear implant users

Mathew

Vickers²,

Boyle³

et al. 2018

Hearing Research

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The plasticity of the auditory system enables it to adjust to electrical stimulation from cochlear implants (CI). Whilst speech perception may develop for many years after implant activation, very little is known about the changes in auditory processing that underpin these improvements. Such an understanding could help guide interventions that improve hearing performance. In this longitudinal study, we examine how electrode discrimination ability changes over time in newly implanted adult CI users. Electrode discrimination was measured with a behavioural task as well as the spatial auditory change complex (ACC), which is a cortical response to a change in place of stimulation. We show that there was significant improvement in electrode discrimination ability over time, though in certain individuals the process of accommodation was slower and more limited. We found a strong relationship between objective and behavioural measures of electrode discrimination using pass-fail rules. In several cases, the development of the spatial ACC preceded accurate behavioural discrimination. These data provide evidence for plasticity of auditory processing in adult CI users. Behavioural electrode discrimination score but not spatial ACC amplitude was found to be a significant predictor of speech perception. We suggest that it would be beneficial to measure electrode discrimination in CI users and that interventions that exploit the plastic capacity of the auditory system to improve basic auditory processing, could be used to optimize performance in CI users.

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Section: A N U S C R I P Tmentioning

confidence: 99%

Section: Participantsmentioning

confidence: 99%

Section: Stimuli For Measuring Electrode Discriminationmentioning

confidence: 99%

Section: Stimuli For Measuring Electrode Discriminationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Development of electrophysiological and behavioural measures of electrode discrimination in adult cochlear implant users

Mathew

Vickers²,

Boyle³

et al. 2018

Hearing Research

Self Cite

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A Site-Selection Strategy Based on Polarity Sensitivity for Cochlear Implants: Effects on Spectro-Temporal Resolution and Speech Perception

Goehring

Archer-Boyd

Deeks

et al. 2019

JARO

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Thresholds of asymmetric pulses presented to cochlear implant (CI) listeners depend on polarity in a way that differs across subjects and electrodes. It has been suggested that lower thresholds for cathodic-dominant compared to anodic-dominant pulses reflect good local neural health. We evaluated the hypothesis that this polarity effect (PE) can be used in a site-selection strategy to improve speech perception and spectro-temporal resolution. Detection thresholds were measured in eight users of Advanced Bionics CIs for 80-pps, triphasic, monopolar pulse trains where the central high-amplitude phase was either anodic or cathodic. Two experimental MAPs were then generated for each subject by deactivating the five electrodes with either the highest or the lowest PE magnitudes (cathodic minus anodic threshold). Performance with the two experimental MAPs was evaluated using two spectro-temporal tests (Spectro-Temporal Ripple for Investigating Processor EffectivenesS (STRIPES; Archer-Boyd et al. in J Acoust Soc Am 144:2983–2997, 2018 ) and Spectral-Temporally Modulated Ripple Test (SMRT; Aronoff and Landsberger in J Acoust Soc Am 134:EL217–EL222, 2013 )) and with speech recognition in quiet and in noise. Performance was also measured with an experimental MAP that used all electrodes, similar to the subjects’ clinical MAP. The PE varied strongly across subjects and electrodes, with substantial magnitudes relative to the electrical dynamic range. There were no significant differences in performance between the three MAPs at group level, but there were significant effects at subject level—not all of which were in the hypothesized direction—consistent with previous reports of a large variability in CI users’ performance and in the potential benefit of site-selection strategies. The STRIPES but not the SMRT test successfully predicted which strategy produced the best speech-in-noise performance on a subject-by-subject basis. The average PE across electrodes correlated significantly with subject age, duration of deafness, and speech perception scores, consistent with a relationship between PE and neural health. These findings motivate further investigations into site-specific measures of neural health and their application to CI processing strategies.

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Using Interleaved Stimulation to Measure the Size and Selectivity of the Sustained Phase-Locked Neural Response to Cochlear Implant Stimulation

Carlyon

Guérit

Deeks

et al. 2021

JARO

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We measured the sustained neural response to electrical stimulation by a cochlear implant (CI). To do so, we interleaved two stimuli with frequencies F1 and F2 Hz and recorded a neural distortion response (NDR) at F2-F1 Hz. We show that, because any one time point contains only the F1 or F2 stimulus, the instantaneous nonlinearities typical of electrical artefact should not produce distortion at this frequency. However, if the stimulus is smoothed, such as by charge integration at the nerve membrane, subsequent (neural) nonlinearities can produce a component at F2-F1 Hz. We stimulated a single CI electrode with interleaved sinusoids or interleaved amplitude-modulated pulse trains such that F2 = 1.5F1, and found no evidence for an NDR when F2-F1 was between 90 and 120 Hz. However, interleaved amplitude-modulated pulse trains with F2-F1~40 Hz revealed a substantial NDR with a group delay of about 45 ms, consistent with a thalamic and/or cortical response. The NDR could be measured even from recording electrodes adjacent to the implant and at the highest pulse rates (> 4000 pps) used clinically. We then measured the selectivity of this sustained response by presenting F1 and F2 to different electrodes and at different between-electrode distances. This revealed a broad tuning that, we argue, reflects the overlap between the excitation elicited by the two electrodes. Our results also provide a glimpse of the neural nonlinearity in the auditory system, unaffected by the biomechanical cochlear nonlinearities that accompany acoustic stimulation. Several potential clinical applications of our findings are discussed.

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Objective assessment of electrode discrimination with the auditory change complex in adult cochlear implant users

Cited by 28 publications

References 58 publications

Development of electrophysiological and behavioural measures of electrode discrimination in adult cochlear implant users

Development of electrophysiological and behavioural measures of electrode discrimination in adult cochlear implant users

A Site-Selection Strategy Based on Polarity Sensitivity for Cochlear Implants: Effects on Spectro-Temporal Resolution and Speech Perception

Using Interleaved Stimulation to Measure the Size and Selectivity of the Sustained Phase-Locked Neural Response to Cochlear Implant Stimulation

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