CURRENT DISTRIBUTIONS IN COCHLEAR STIMULATIONa

Black, R. C.; Clark, Graeme M.; Tong, Y. C.; Patrick, J.

doi:10.1111/j.1749-6632.1983.tb31626.x

Cited by 47 publications

(39 citation statements)

References 6 publications

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“…The latter finding is consistent with previous reports that current attenuates two to three times more rapidly for bipolar stimulation than for monopolar stimulation with increasing distance from the source (Black and Clark, 1980;Black et al, 1981Black et al, , 1983O'Leary et al, 1985;Hartmann and Klinke, 1990;Kral et al, 1998). That finding is also consistent with most previous studies that employed psychophysical forward masking patterns to examine spread of excitation across the electrode array (Shannon, 1983b;Lim et al, 1989;Boex et al, 2003;Chatterjee et al, 2006).…”

Section: A Characteristics Of Fmstcs In Electrical Hearingsupporting

confidence: 82%

“…Early studies reported length constants of approximately 3 mm for bipolar stimulation and 10 mm for monopolar stimulation (Black and Clark, 1980;Black et al, 1981Black et al, , 1983O'Leary et al, 1985). More recent studies which measured primary auditory nerve responses in cat as a function of electrode position have reported attenuation slopes of about 8 dB/mm for bipolar stimulation and 3 dB/mm for monopolar stimulation (Hartmann and Klinke, 1990;Kral et al, 1998).…”

Section: E Factors Influencing Stc Shapesmentioning

confidence: 99%

“…If no nerve fibers exist near a particular electrode, then current delivered through that electrode will necessarily stimulate auditory fibers that are apical and/or basal to the intended location. Second, structural changes to the cochlea following deafness and cochlear implantation may result in irregularities in the impedance pathways that govern current flow (Spelman et al, 1982;Black et al, 1983;Shepherd et al, 1994;Jolly, 1998;Hughes et al, 2001;Saunders et al, 2002). This may result in stimulation of auditory nerve fibers remote from the electrode contact in either the apical or basal direction.…”

Section: Introductionmentioning

confidence: 99%

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Forward-masked spatial tuning curves in cochlear implant users

Nelson

Donaldson

Kreft

2008

The Journal of the Acoustical Society of America

119

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Forward-masked psychophysical spatial tuning curves (fmSTCs) were measured in twelve cochlearimplant subjects, six using bipolar stimulation (Nucleus devices)and six using monopolar stimulation (Clarion devices). fmSTCs were measured at several probe levels on a middle electrode using a fixedlevel probe stimulus and variable-level maskers. The average fmSTC slopes obtained in subjects using bipolar stimulation (3.7 dB/mm) were approximately three times steeper than average slopes obtained in subjects using monopolar stimulation (1.2 dB/mm). Average spatial bandwidths were about half as wide for subjects with bipolar stimulation (2.6 mm) than for subjects with monopolar stimulation (4.6 mm). None of the tuning curve characteristics changed significantly with probe level. fmSTCs replotted in terms of acoustic frequency, using Greenwood's [J. Acoust. Soc. Am. 33, 1344-1356 (1961)] frequency-to-place equation, were compared with forward-masked psychophysical tuning curves obtained previously from normal-hearing and hearing-impaired acoustic listeners. The average tuning characteristics of fmSTCs in electric hearing were similar to the broad tuning observed in normal-hearing and hearing-impaired acoustic listeners at high stimulus levels. This suggests that spatial tuning is not the primary factor limiting speech perception in many cochlear implant users.

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Section: A Characteristics Of Fmstcs In Electrical Hearingsupporting

confidence: 82%

Section: E Factors Influencing Stc Shapesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Forward-masked spatial tuning curves in cochlear implant users

Nelson

Donaldson

Kreft

2008

The Journal of the Acoustical Society of America

119

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“…The approaches used in these studies range from saline tank/resistive network models of voltage distributions within the cochlea (Strelioff 1973;Black and Clark 1980;Black et al 1981Black et al , 1983O'Leary et al 1985;Girizon 1987;Ifukbe and White 1987;Kasper et al 1991;Suesserman and Spelman 1993;Jolly et al 1996;Kral et al 1998) to 2D and 3D computer simulations of intracochlear stimulation. These computer simulations attempt to model in vivo spatial excitation patterns produced by single electrodes in the spiral of the auditory nerve array (Finley 1989;Finley et al 1987Finley et al , 1990Frijns et al 1994Frijns et al , 1995Frijns et al , 1996Rattay et al 2001a,b).…”

Section: Modeling Studiesmentioning

confidence: 99%

Topographic Spread of Inferior Colliculus Activation in Response to Acoustic and Intracochlear Electric Stimulation

Snyder

Bierer

Middlebrooks

2004

JARO

140

158

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The design of contemporary multichannel cochlear implants is predicated on the presumption that they activate multiple independent sectors of the auditory nerve array. The independence of these channels, however, is limited by the spread of activation from each intracochlear electrode across the auditory nerve array. In this study, we evaluated factors that influence intracochlear spread of activation using two types of intracochlear electrodes: (1) a clinical-type device consisting of a linear series of ring contacts positioned along a silicon elastomer carrier, and (2) a pair of visually placed (VP) ball electrodes that could be positioned independently relative to particular intracochlear structures, e.g., the spiral ganglion. Activation spread was estimated by recording multineuronal evoked activity along the cochleotopic axis of the central nucleus of the inferior colliculus (ICC). This activity was recorded using silicon-based singleshank, 16-site recording probes, which were fixed within the ICC at a depth defined by responses to acoustic tones. After deafening, electric stimuli consisting of single biphasic electric pulses were presented with each electrode type in various stimulation configurations (monopolar, bipolar, tripolar) and/or various electrode orientations (radial, off-radial, longitudinal). The results indicate that monopolar (MP) stimulation with either electrode type produced widepread excitation across the ICC. Bipolar (BP) stimulation with banded pairs of electrodes oriented longitudinally produced activation that was somewhat less broad than MP stimulation, and tripolar (TP) stimulation produced activation that was more restricted than MP or BP stimulation. Bipolar stimulation with radially oriented pairs of VP ball electrodes produced the most restricted activation. The activity patterns evoked by radial VP balls were comparable to those produced by pure tones in normal-hearing animals. Variations in distance between radially oriented VP balls had little effect on activation spread, although increases in interelectrode spacing tended to reduce thresholds. Bipolar stimulation with longitudinally oriented VP electrodes produced broad activation that tended to broaden as the separation between electrodes increased.

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“…However, in cases of extremely steep slopes or when the tested electrodes had larger physical separations, only two masked thresholds were included. The fitted slopes are expressed in units of decibels per millimeter to reflect a logarithmic decay in masker current with distance in mm (Black et al, 1983). The spatial bandwidth of the fmSTC was calculated as the distance (in mm) between the apical and basal fitted slopes at an amplitude 1 dB above the minimum masker level at the tip of the tuning curve.…”

Section: Curve-fitting Proceduresmentioning

confidence: 99%

Spatial tuning curves from apical, middle, and basal electrodes in cochlear implant users

Nelson¹,

Kreft²,

Anderson³

et al. 2011

The Journal of the Acoustical Society of America

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Forward-masked psychophysical spatial tuning curves (fmSTCs) were measured in 15 cochlearimplant subjects, 10 using monopolar stimulation and 5 using bipolar stimulation. In each subject, fmSTCs were measured at several probe levels on an apical, middle, and basal electrode using a fixed-level probe stimulus and variable-level maskers. Tuning curve slopes and bandwidths did not change significantly with probe level for electrodes located in the apical, middle, or basal region although a few subjects exhibited dramatic changes in tuning at the extremes of the probe level range. Average tuning curve slopes and bandwidths did not vary significantly across electrode regions. Spatial tuning curves were symmetrical and similar in width across the three electrode regions. However, several subjects demonstrated large changes in slope and=or bandwidth across the three electrode regions, indicating poorer tuning in localized regions of the array. Cochlearimplant users exhibited bandwidths that were approximately five times wider than normal-hearing acoustic listeners but were in the same range as acoustic listeners with moderate cochlear hearing loss. No significant correlations were found between spatial tuning parameters and speech recognition; although a weak relation was seen between middle electrode tuning and transmitted information for vowel second formant frequency.

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CURRENT DISTRIBUTIONS IN COCHLEAR STIMULATIONa

Cited by 47 publications

References 6 publications

Forward-masked spatial tuning curves in cochlear implant users

Forward-masked spatial tuning curves in cochlear implant users

Topographic Spread of Inferior Colliculus Activation in Response to Acoustic and Intracochlear Electric Stimulation

Spatial tuning curves from apical, middle, and basal electrodes in cochlear implant users

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