Current-level discrimination using bipolar and monopolar electrode configurations in cochlear implants

Drennan, Ward R.; Pfingst, Bryan E.

doi:10.1016/j.heares.2004.11.010

Cited by 16 publications

(16 citation statements)

References 28 publications

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“…However, this depends on whether or not the dynamic range, which we could not obtain because of our maximum current limit, increases proportionally with JND level step size. This also depends on whether level discrimination is based on a logarithmic scale (Nelson et al, 1996;Drennan and Pfingst, 2005) for which we did not observe any significant location effects with our methods. In terms of temporal coding properties, stimulation of more rostral and ventral regions usually elicited cortical activity with shorter latencies and greater spiking precision.…”

Section: Organization Within An Icc Laminamentioning

confidence: 73%

Spatially Distinct Functional Output Regions within the Central Nucleus of the Inferior Colliculus: Implications for an Auditory Midbrain Implant

Lim¹,

Anderson²

2007

J. Neurosci.

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The inferior colliculus central nucleus (ICC) has potential as a new site for an auditory prosthesis [i.e., auditory midbrain implant (AMI)]for deaf patients who cannot benefit from cochlear implants (CIs). We have previously shown that ICC stimulation achieves lower thresholds, greater dynamic ranges, and more localized, frequency-specific primary auditory cortex (A1) activation than CI stimulation. However, we also observed that stimulation location along the caudorostral (isofrequency) dimension of the ICC affects thresholds and frequency specificity in A1, suggesting possible differences in functional (output) organization within the ICC. In this study, we electrically stimulated different regions along the isofrequency laminas of the ICC and recorded the corresponding A1 activity in ketamineanesthetized guinea pigs using multisite probes to systematically assess ICC stimulation location effects. Our results indicate that stimulation of more rostral and somewhat ventral regions within an ICC lamina achieves lower thresholds, smaller discriminable level steps, and larger evoked potentials in A1. We also observed longer first spike latencies, which correlated with reduced spiking precision, when stimulating in more caudal and dorsal ICC regions. These findings suggest that at least two spatially distinct functional output regions exist along an ICC lamina: a caudal-dorsal region and a rostral-ventral region. The AMI will be implanted along the tonotopic axis of the ICC to achieve frequency-specific activation. However, stimulation location along the ICC laminas affects response properties that have shown to be important for speech perception performance, and needs to be considered when implanting future AMI patients.

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Section: Organization Within An Icc Laminamentioning

confidence: 73%

Spatially Distinct Functional Output Regions within the Central Nucleus of the Inferior Colliculus: Implications for an Auditory Midbrain Implant

Lim¹,

Anderson²

2007

J. Neurosci.

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“…Another question is whether discriminable level steps follow a logarithmic scale. CI studies have shown that Weber fractions tend to decrease with stimulus level and absolute thresholds (Drennan and Pfingst 2005;Nelson et al 1996;Pfingst et al 1983). It is possible that the Weber fractions for cochlear FIG. 11.…”

Section: Discussionmentioning

confidence: 98%

Antidromic Activation Reveals Tonotopically Organized Projections From Primary Auditory Cortex to the Central Nucleus of the Inferior Colliculus in Guinea Pig

Lim¹,

Anderson²

2007

Journal of Neurophysiology

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. Auditory cortical responses to electrical stimulation of the inferior colliculus: implications for an auditory midbrain implant. J Neurophysiol 96: 975-988, 2006. First published May 24, 2006 doi:10.1152/jn.01112.2005. The success and limitations of cochlear implants (CIs) along with recent advances in deep brain stimulation and neural engineering have motivated the development of a central auditory prosthesis. In this study, we investigated the effects of electrical stimulation of the inferior colliculus central nucleus (ICC) on primary auditory cortex (A1) activity to determine the potential benefits of an auditory midbrain implant (AMI). We recorded multiunit activity in A1 of ketamine-anesthetized guinea pigs in response to single-pulse (200 s/phase) monopolar stimulation of the ICC using multisite silicon-substrate probes. We then compared measures of threshold, dynamic range, and tonotopic spread of activation for ICC stimulation with that of published data for CI stimulation. Our results showed that compared with cochlear stimulation, ICC stimulation achieved: 1) thresholds about 8 dB lower; 2) dynamic ranges Ն4 dB greater; and 3) more localized, frequency-specific activation, even though frequency specificity was partially lost at higher stimulus levels for low-frequency ICC regions. Our results also showed that stimulation of rostral ICC regions elicited lower thresholds but with greater activation spread along the tonotopic gradient of A1 than did stimulation of more caudal regions. These results suggest that an AMI may improve frequency and level coding with lower energy requirements compared with CIs. However, a trade-off between lower perceptual thresholds and better frequency discrimination may exist that depends on location of stimulation along the caudorostral dimension of the ICC. Overall, this study provides the foundation for future AMI research and development.

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“…If listeners based a decision in this task on overall loudness changes, the model predicts that sensitivity would get worse. Additionally, in single-electrode current-level discrimination experiments, sensitivity usually decreases with decreases in current level (Nelson et al 1996;Drennan and Pfingst 2005). Thus, the main effects of Experiment 1 appeared to be attributable to the decrease in current level of the target, and consequently a decrease in its contribution to overall loudness as the number of electrodes increased.…”

Section: Methodsmentioning

confidence: 99%

“…Studies by Nelson et al (1996) and Drennan and Pfingst (2005) investigated current-level discrimination ability in cochlear implantees at single stimulation sites when no other electrodes were stimulated. However, in common sound processing schemes, such as continuous interleaved sampling (CIS), SPEAK, and ACE (Wilson et al 1991;Skinner et al 2002), multiple electrodes are stimulated.…”

Section: Introductionmentioning

confidence: 99%

Current-Level Discrimination in the Context of Interleaved, Multichannel Stimulation in Cochlear Implants: Effects of Number of Stimulated Electrodes, Pulse Rate, and Electrode Separation

Drennan

Pfingst

2006

JARO

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The ability of cochlear implantees to detect an increment in current level at one of many stimulated electrodes was investigated. Such changes in the electric profile provide information for cochlear implantees to discriminate numerous sounds, especially vowels. In Experiment 1, sensitivity to increases in current level at one stimulation site in the electric profile decreased as the number of stimulated electrodes increased. This outcome was most likely a result of decreased stimulus levels at individual electrodes that were required to retain a comfortable loudness when the number of active electrodes was increased. Experiment 2 investigated the effects of pulse rate and separation between stimulation sites when the levels in percent of dynamic range and number of stimulated electrodes were held constant. The effect of pulse rate and electrode separation varied among listeners. The sensitivity of 6 of 9 listeners was best at the pulse rate that they used clinically. This might have been the result of adaptation to the clinical pulse rate, or listeners might have chosen their inherently best pulse rate during the clinical fitting.

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Current-level discrimination using bipolar and monopolar electrode configurations in cochlear implants

Cited by 16 publications

References 28 publications

Spatially Distinct Functional Output Regions within the Central Nucleus of the Inferior Colliculus: Implications for an Auditory Midbrain Implant

Spatially Distinct Functional Output Regions within the Central Nucleus of the Inferior Colliculus: Implications for an Auditory Midbrain Implant

Antidromic Activation Reveals Tonotopically Organized Projections From Primary Auditory Cortex to the Central Nucleus of the Inferior Colliculus in Guinea Pig

Current-Level Discrimination in the Context of Interleaved, Multichannel Stimulation in Cochlear Implants: Effects of Number of Stimulated Electrodes, Pulse Rate, and Electrode Separation

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