Perceptual Interactions Between Electrodes Using Focused and Monopolar Cochlear Stimulation

Marozeau, Jérémy; McDermott, Hugh J.; Swanson, Brett A.; McKay, Colette M.

doi:10.1007/s10162-015-0511-2

Cited by 33 publications

(38 citation statements)

References 26 publications

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“…They measured place specificity in terms of the function relating performance to electrode separation and found no difference between the two stimulation modes. A similar negative finding was obtained by Marozeau et al ( 2015 ) when comparing AP and MP modes. It is not clear why the conclusions have differed somewhat across studies.…”

Section: Discussionsupporting

confidence: 88%

Spatial Selectivity in Cochlear Implants: Effects of Asymmetric Waveforms and Development of a Single-Point Measure

Carlyon

Deeks

Undurraga

et al. 2017

JARO

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Three experiments studied the extent to which cochlear implant users’ spatial selectivity can be manipulated using asymmetric waveforms and tested an efficient method for comparing spatial selectivity produced by different stimuli. Experiment 1 measured forward-masked psychophysical tuning curves (PTCs) for a partial tripolar (pTP) probe. Maskers were presented on bipolar pairs separated by one unused electrode; waveforms were either symmetric biphasic (“SYM”) or pseudomonophasic with the short high-amplitude phase being either anodic (“PSA”) or cathodic (“PSC”) on the more apical electrode. For the SYM masker, several subjects showed PTCs consistent with a bimodal excitation pattern, with discrete excitation peaks on each electrode of the bipolar masker pair. Most subjects showed significant differences between the PSA and PSC maskers consistent with greater masking by the electrode where the high-amplitude phase was anodic, but the pattern differed markedly across subjects. Experiment 2 measured masked excitation patterns for a pTP probe and either a monopolar symmetric biphasic masker (“MP_SYM”) or pTP pseudomonophasic maskers where the short high-amplitude phase was either anodic (“TP_PSA”) or cathodic (“TP_PSC”) on the masker’s central electrode. Four of the five subjects showed significant differences between the masker types, but again the pattern varied markedly across subjects. Because the levels of the maskers were chosen to produce the same masking of a probe on the same channel as the masker, it was correctly predicted that maskers that produce broader masking patterns would sound louder. Experiment 3 exploited this finding by using a single-point measure of spread of excitation to reveal significantly better spatial selectivity for TP_PSA compared to TP_PSC maskers.

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Section: Discussionsupporting

confidence: 88%

Spatial Selectivity in Cochlear Implants: Effects of Asymmetric Waveforms and Development of a Single-Point Measure

Carlyon

Deeks

Undurraga

et al. 2017

JARO

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“…In addition to the limited number of electrodes, the shallow insertion depth of the array and differences in local neural survival, one major cause for the poor spectral and temporal resolution of CI users is the spread of current along the cochlea. This current spread causes broad regions of the auditory nerve to be stimulated when activating a single electrode, and numerous psychophysical studies have demonstrated substantial interactions when activating two or more channels (Marozeau et al, 2015;McKay et al, 2001;McKay and McDermott, 1996;Shannon, 1983;Townshend et al, 1987).…”

Section: Introductionmentioning

confidence: 99%

The effect of a coding strategy that removes temporally masked pulses on speech perception by cochlear implant users

Lamping¹,

Goehring²,

Marozeau³

et al. 2020

Preprint

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Speech recognition in noisy environments remains a challenge for cochlear implant (CI) recipients. Unwanted charge interactions between current pulses in the same and across different electrode channels are likely to impair performance. Here we investigate the effect of reducing the number of current pulses on speech perception. This was achieved by implementing a psychoacoustic temporal-masking model where current pulses in each channel were passed through a temporal integrator to identify and remove pulses that were less likely to be perceived by the recipient. The decision criterion of the temporal integrator was varied to control the percentage of pulses removed in each condition. In experiment 1, speech in quiet was processed with a standard Continuous Interleaved Sampling (CIS) strategy and with 25, 50 and 75% of pulses removed. In experiment 2, performance was measured for speech in noise with the CIS reference and with 50 and 75% of pulses removed. Speech intelligibility in quiet revealed no significant difference between reference and test conditions. For speech in noise, results showed a significant improvement of 2.4 dB when removing 50% of pulses. Performance both in quiet and in noise was not significantly different between the reference and when 75% of pulses were removed. Further, by reducing the overall amount of current pulses by 25, 50, and 75% but accounting for the increase in charge necessary to compensate for the decrease in loudness, estimated average power savings of 21.15, 40.95, and 63.45%, respectively, could be possible for this set of listeners. In conclusion, removing temporally masked pulses may improve speech perception in noise and result in substantial power savings.

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“…Current-focusing using FMP stimulation has been shown to be effective at restricting the field of excitation in modelling (Frijns et al, 2011), acute preclinical studies (George et al, 2015a, George et al, 2014) and initial clinical trials (Long et al, 2014, Marozeau et al, 2015). Although shown to be a promising stimulation strategy, there has been no evaluation of the underlying long-term safety issues associated with this approach.…”

Section: Introductionmentioning

confidence: 99%

Evaluation of focused multipolar stimulation for cochlear implants: a preclinical safety study

et al. 2017

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Objective Cochlear Implants (CIs) have a limited number of independent stimulation channels due to the highly conductive nature of the fluid-filled cochlea. Attempts to develop highly focused stimulation to improve speech perception in CI users includes the use of simultaneous stimulation via multiple current sources. Focused multipolar (FMP) stimulation is an example of this approach and has been shown to reduce interaction between stimulating channels. However, compared with conventional biphasic current pulses generated from a single current source, FMP is a complex stimulus that includes extended periods of stimulation before charge recovery is achieved, raising questions on whether chronic stimulation with this strategy is safe. The present study evaluated the long-term safety of intracochlear stimulation using FMP in a preclinical animal model of profound deafness. Approach Six cats were bilaterally implanted with scala tympani electrode arrays two months after deafening, and received continuous unilateral FMP stimulation at levels that evoked a behavioural response for periods of up to 182 days. Electrode impedance, electrically-evoked compound action potentials (ECAPs) and auditory brainstem responses (EABRs) were monitored periodically over the course of the stimulation program from both the stimulated and contralateral control cochleae. On completion of the stimulation program cochleae were examined histologically and the electrode arrays were evaluated for evidence of platinum (Pt) corrosion. Main results There was no significant difference in electrode impedance between control and chronically stimulated electrodes following long-term FMP stimulation. Moreover, there was no significant difference between ECAP and EABR thresholds evoked from control or stimulated cochleae at either the onset of stimulation or at completion of the stimulation program. Chronic FMP stimulation had no effect on spiral ganglion neuron (SGN) survival when compared with unstimulated control cochleae. Long-term implantation typically evoked a mild foreign body reaction proximal to the electrode array; however stimulated cochleae exhibited a small but statistically significant increase in the tissue response. Finally, there was no evidence of Pt corrosion following long-term FMP stimulation; stimulated electrodes exhibited the same surface features as the unstimulated control electrodes. Significance Chronic intracochlear FMP stimulation at levels used in the present study did not adversely affect electrically-evoked neural thresholds or SGN survival but evoked a small, benign increase in inflammatory response compared to control ears. Moreover chronic FMP stimulation does not affect the surface of Pt electrodes at suprathreshold stimulus levels. These findings support the safe clinical application of an FMP stimulation strategy.

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Perceptual Interactions Between Electrodes Using Focused and Monopolar Cochlear Stimulation

Cited by 33 publications

References 26 publications

Spatial Selectivity in Cochlear Implants: Effects of Asymmetric Waveforms and Development of a Single-Point Measure

Spatial Selectivity in Cochlear Implants: Effects of Asymmetric Waveforms and Development of a Single-Point Measure

The effect of a coding strategy that removes temporally masked pulses on speech perception by cochlear implant users

Evaluation of focused multipolar stimulation for cochlear implants: a preclinical safety study

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