Current Steering and Current Focusing in Cochlear Implants: Comparison of Monopolar, Tripolar, and Virtual Channel Electrode Configurations

Berenstein, Carlo K.; Mens, L.H.M.; Mulder, Jef J. S.; Vanpoucke, Filiep

doi:10.1097/aud.0b013e3181645336

Cited by 145 publications

(162 citation statements)

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“…During the past several years, increasing attention has been devoted to representing "fine structure" or "fine frequency" information with CIs (e.g., Smith et al, 2002;Nie et al, 2005;Wilson et al, 2005;Zeng et al, 2005;Hochmair et al, 2006;Arnoldner et al, 2007;Berenstein et al, 2008;Brendel et al, 2008;Buechner et al, 2008;Litvak et al, 2008;Bonham and Litvak, this issue). These recent efforts are reviewed and discussed in Wilson and Dorman (2008b, c).…”

Section: Processing Strategies For Cochlear Implantsmentioning

confidence: 99%

Cochlear implants: A remarkable past and a brilliant future

2008

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The aims of this paper are to (i) provide a brief history of cochlear implants; (ii) present a status report on the current state of implant engineering and the levels of speech understanding enabled by that engineering; (iii) describe limitations of current signal processing strategies and (iv) suggest new directions for research. With current technology the "average" implant patient, when listening to predictable conversations in quiet, is able to communicate with relative ease. However, in an environment typical of a workplace the average patient has a great deal of difficulty. Patients who are "above average" in terms of speech understanding, can achieve 100% correct scores on the most difficult tests of speech understanding in quiet but also have significant difficulty when signals are presented in noise. The major factors in these outcomes appear to be (i) a loss of low-frequency, fine structure information possibly due to the envelope extraction algorithms common to cochlear implant signal processing; (ii) a limitation in the number of effective channels of stimulation due to overlap in electric fields from electrodes, and (iii) central processing deficits, especially for patients with poor speech understanding. Two recent developments, bilateral implants and combined electric and acoustic stimulation, have promise to remediate some of the difficulties experienced by patients in noise and to reinstate low-frequency fine structure information. If other possibilities are realized, e.g., electrodes that emit drugs to inhibit cell death following trauma and to induce the growth of neurites toward electrodes, then the future is very bright indeed.

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Section: Processing Strategies For Cochlear Implantsmentioning

confidence: 99%

Cochlear implants: A remarkable past and a brilliant future

2008

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“…While these improvements in simulation are intriguing, there remain considerable practical difficulties associated with increasing fine-structure detail for CI users. Ongoing efforts to increase fine structure via the creation of "virtual" electrodes (e.g., McDermott and McKay, 1994;Geurts and Wouters, 2004;Firszt et al, 2007;Berenstein et al, 2008;Landsberger and Srinivasan, 2009) or the provision of fine temporal detail (e.g., Rubinstein et al, 1999;Arnoldner et al, 2007;Riss et al, 2009) have met with limited success. In general, results show some improvement in pitch detection or discrimination, but limited gains to speech reception in noise (Berenstein et al, 2008;Firszt et al, 2009;Han et al, 2009;Riss et al, 2009;Shannon et al, 2011).…”

Section: Introductionmentioning

confidence: 99%

Comparing the effects of reverberation and of noise on speech recognition in simulated electric-acoustic listening

Tillery¹,

Brown²,

Bacon³

2012

The Journal of the Acoustical Society of America

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Cochlear implant users report difficulty understanding speech in both noisy and reverberant environments. Electric-acoustic stimulation (EAS) is known to improve speech intelligibility in noise. However, little is known about the potential benefits of EAS in reverberation, or about how such benefits relate to those observed in noise. The present study used EAS simulations to examine these questions. Sentences were convolved with impulse responses from a model of a room whose estimated reverberation times were varied from 0 to 1 sec. These reverberated stimuli were then vocoded to simulate electric stimulation, or presented as a combination of vocoder plus low-pass filtered speech to simulate EAS. Monaural sentence recognition scores were measured in two conditions: reverberated speech and speech in a reverberated noise. The long-term spectrum and amplitude modulations of the noise were equated to the reverberant energy, allowing a comparison of the effects of the interferer (speech vs noise). Results indicate that, at least in simulation, (1) EAS provides significant benefit in reverberation; (2) the benefits of EAS in reverberation may be underestimated by those in a comparable noise; and (3) the EAS benefit in reverberation likely arises from partially preserved cues in this background accessible via the low-frequency acoustic component.

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“…In summary, both the model and psychophysical data verified the feasibility and efficacy of pTP-mode current steering, which can be readily incorporated into the pTP-mode processing strategies (e.g., Berenstein et al 2008) to improve CI performance. For example, Bierer and Faulkner (2010) argued that with the more focused standard pTP mode, CI users were more susceptible to cochlear "dead regions," which required more current to reach T/C levels and had less spatial selectivity of electric stimulation.…”

Section: General Discussion and Summarymentioning

confidence: 54%

“…The stimulation mode changes from full MP to full TP as σ varies from 0 to 1. Although spectral ripple discrimination improved with σ00.75, speech recognition was similar with pTP or MP stimulation (Berenstein et al 2008). With focused pTP mode, CI users were more susceptible to poor electrode-neuron interface (Bierer 2010), which may adversely affect the perception of certain frequency information.…”

Section: Introductionmentioning

confidence: 99%

Current Steering with Partial Tripolar Stimulation Mode in Cochlear Implants

Luo

2012

JARO

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The large spread of excitation is a major cause of poor spectral resolution for cochlear implant (CI) users. Partial tripolar (pTP) mode has been proposed to reduce current spread by returning an equally distributed fraction (0.5×σ) of current to two flanking electrodes and the rest to an extra-cochlear ground. This study tested the efficacy of incorporating current steering into pTP mode to add spectral channels. Different proportions of current [α×σ and (1−α)×σ] were returned to the basal and apical flanking electrodes respectively to shape the electric field. Loudness and pitch perception with α from 0 to 1 in steps of 0.1 was simulated with a computational model of CI stimulation and tested on the apical, middle, and basal electrodes of six CI subjects. The highest σ allowing for full loudness growth within the implant compliance limit was chosen for each main electrode. Pitch ranking was measured between pairs of loudness-balanced steered pTP stimuli with an α interval of 0.1 at the most comfortable level. Results demonstrated that steered pTP stimuli with α around 0.5 required more current to achieve equal loudness than those with α around 0 or 1, maybe due to more focused excitation patterns. Subjects usually perceived decreasing pitches as α increased from 0 to 1, somewhat consistent with the apical shift of the center of gravity of excitation pattern in the model. Pitch discrimination was not better with α around 0.5 than with α around 0 or 1, except for some subjects and electrodes. For three subjects with better pitch discrimination, about half of the pitch ranges of two adjacent main electrodes overlapped with each other in steered pTP mode. These results suggest that current steering with focused pTP mode may improve spectral resolution and pitch perception with CIs.

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Current Steering and Current Focusing in Cochlear Implants: Comparison of Monopolar, Tripolar, and Virtual Channel Electrode Configurations

Cited by 145 publications

References 40 publications

Cochlear implants: A remarkable past and a brilliant future

Cochlear implants: A remarkable past and a brilliant future

Comparing the effects of reverberation and of noise on speech recognition in simulated electric-acoustic listening

Current Steering with Partial Tripolar Stimulation Mode in Cochlear Implants

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