Conditions for Generating Virtual Channels in Cochlear Prosthesis Systems

Choi, C.T.M.; Hsu, Cheng Hsiung

doi:10.1007/s10439-008-9622-9

Cited by 26 publications

(12 citation statements)

References 18 publications

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“…Finally, “current steering” uses separate current sources to stimulate two electrodes simultaneously, typically in phase (Firszt et al, 2007; Koch et al, 2007; Bonham and Litvak, 2008; Choi and Hsu, 2009; Frijns et al, 2009; Saoji et al, 2009). Pitch percepts can change as the ratio of total current is varied between the two physical electrodes because the shape of the summed electrical field changes, altering the resulting neural excitation patterns.…”

Section: Introductionmentioning

confidence: 99%

ECAP spread of excitation with virtual channels and physical electrodes

et al. 2013

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The primary goal of this study was to evaluate physiological spatial excitation patterns for stimulation of adjacent physical electrodes and intermediate virtual channels. Two experiments were conducted that utilized electrically evoked compound action potential (ECAP) spread-of-excitation (SOE) functions obtained with the traditional forward-masking subtraction method. These two experiments examined spatial excitation patterns for virtual-channel maskers and probes, respectively. In Experiment 1, ECAP SOE patterns were obtained for maskers applied to physical electrodes and virtual channels to determine whether virtual-channel maskers yield SOE patterns similar to those predicted from physical electrodes. In Experiment 2, spatial separation of SOE functions was compared for two adjacent physical probe electrodes and the intermediate virtual channel to determine the extent to which ECAP SOE patterns for virtual-channel probes are spatially separate from those obtained with physical electrodes. Data were obtained for three electrode regions (basal, middle, apical) for 35 ears implanted with Cochlear (N = 16) or Advanced Bionics (N = 19) devices. Results from Experiment 1 showed no significant difference between predicted and measured ECAP amplitudes for Advanced Bionics subjects. Measured ECAP amplitudes for virtual-channel maskers were significantly larger than the predicted amplitudes for Cochlear subjects; however, the difference was <2 μV and thus is likely not clinically significant. Results from Experiment 2 showed that the probe set in the apical region demonstrated the least amount of spatial separation amongst SOE functions, which may be attributed to more uniform nerve survival patterns, closer electrode spacing, and/or the tapered geometry of the cochlea. As expected, adjacent physical probes demonstrated greater spatial separation than for comparisons between each physical probe and the intermediate virtual channel. Finally, the virtual-channel SOE functions were generally weighted toward the basal electrode in the pair.

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Section: Introductionmentioning

confidence: 99%

ECAP spread of excitation with virtual channels and physical electrodes

et al. 2013

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“…The ratio of current can then be varied between the two electrodes to produce systematic changes in the shape of the electric field and subsequent neural recruitment patterns. This method has been referred to as “current steering” (Firszt et al, 2007; Koch et al, 2007; Bonham & Litvak, 2008; Choi & Hsu, 2009; Frijns et al, 2009; Saoji et al, 2009) and can be used with devices having individual current sources for each electrode, such as the Advanced Bionics (AB) and Med-El I 100 devices. With current steering, Firszt et al (2007) reported an average of 5.3, 6.0, and 3.8 discriminable steps between adjacent physical electrodes for apical, middle, and basal electrode pairs, respectively.…”

Section: Introductionmentioning

confidence: 99%

Electrically Evoked Compound Action Potential Measures for Virtual Channels Versus Physical Electrodes

Hughes

Goulson

2011

Ear &Amp; Hearing

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Objectives-The number of distinct pitch percepts for cochlear implant (CI) listeners is somewhat limited by the number of physical electrodes in the array. Newer-generation CIs have the capability to potentially increase this number by stimulating areas of the cochlea between the physical electrodes. Currently this is achieved by electrically coupling adjacent electrodes or by simultaneously activating two electrodes with independent current sources (i.e., "current steering"). Presumably, either type of dual-electrode stimulation will generate neural excitation patterns that are intermediate to those generated by either physical electrode alone (henceforth termed virtual channel). However, it is not clear whether virtual-channel stimulation yields neural recruitment patterns with similar shapes and rates of growth as compared with each physical electrode alone. The purpose of this study was to compare basic electrically evoked compound action potential (ECAP) measures for physical electrodes and virtual channels to determine whether properties of the respective excitation patterns were similar.Design-Data were collected for 12 adult CI recipients (N = 6 Nucleus Freedom CI24RE, N = 2 Advanced Bionics HiResolution 90K, N = 4 Advanced Bionics CII). ECAP responses were measured for a set of three adjacent physical electrodes and two corresponding intermediate virtual channels (e.g., physical electrodes 4, 5, and 6 and virtual channels 4+5 and 5+6) at three positions along the electrode array (basal, middle, and apical). Virtual channels for Nucleus subjects were produced via electrical coupling of adjacent electrode pairs ("dual-electrode mode"). For AB subjects, virtual channels were produced via simultaneous, in-phase stimulation of adjacent electrode pairs with 50 % of the total current delivered to each electrode in the pair. Specific ECAP measures were: (1) threshold and slope of the input/output (I/O) functions, (2) amplitude for a masker-probe interval of 1500 μsec (measure of refractory recovery), and (3) the relative location of spread-of-excitation (SOE) functions among virtual channels and adjacent physical electrodes. Measures for virtual channels were compared with those for the flanking physical electrodes using a multivariate analysis of variance.Results-There were no statistically significant differences between physical electrodes and virtual channels for ECAP thresholds, slope of the I/O function, or refractory recovery. On average, SOE functions for the virtual channels were spatially located approximately halfway between SOE functions for the adjacent physical electrodes.Conclusions-Results from this study suggest that virtual channels produce neural recruitment patterns with properties similar to those elicited by the adjacent physical electrodes.

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“…Four-electrode current steering schemes (FECSS) is a current steering technique developed to control four adjacent electrodes simultaneously (Choi & Hsu, reviewing;Choi & Hsu, 2009). As shown in Fig.…”

Section: Hires120 (Koch Et Al 2004)mentioning

confidence: 99%