Higher Sensitivity of Human Auditory Nerve Fibers to Positive Electrical Currents

Macherey, Olivier; Carlyon, Robert P.; Wieringen, Astrid Van; Deeks, John M.; Wouters, Jan

doi:10.1007/s10162-008-0112-4

Cited by 107 publications

(142 citation statements)

References 36 publications

(76 reference statements)

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“…For example, in the simplest case, by stimulating with monophasic pulses using computational models of cat and human SGNs, Rattay et al (2001) demonstrated that while model cat SGNs were more easily excited with the cathodic polarity, model human nerves displayed greater sensitivity to the anodic pulse. This result was confirmed in humans with biphasic pulses (Macherey et al 2008). Therefore, care should be taken in generalizing across stimulation pulse type and species with respect to the response properties of refractoriness, facilitation, accommodation, and spike rate adaptation, because the site of action potential initiation or the patterns of subthreshold depolarizations and hyperpolarizations along an axon will be dependent on the exact electrode-neuron geometry and the pulse waveform.…”

Section: Spatial Effects Of CI Stimulation Related To Temporal Interamentioning

confidence: 62%

Temporal Considerations for Stimulating Spiral Ganglion Neurons with Cochlear Implants

Boulet

White

Bruce

2015

JARO

103

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A wealth of knowledge about different types of neural responses to electrical stimulation has been developed over the past 100 years. However, the exact forms of neural response properties can vary across different types of neurons. In this review, we survey four stimulus-response phenomena that in recent years are thought to be relevant for cochlear implant stimulation of spiral ganglion neurons (SGNs): refractoriness, facilitation, accommodation, and spike rate adaptation. Of these four, refractoriness is the most widely known, and many perceptual and physiological studies interpret their data in terms of refractoriness without incorporating facilitation, accommodation, or spike rate adaptation. In reality, several or all of these behaviors are likely involved in shaping neural responses, particularly at higher stimulation rates. A better understanding of the individual and combined effects of these phenomena could assist in developing improved cochlear implant stimulation strategies. We review the published physiological data for electrical stimulation of SGNs that explores these four different phenomena, as well as some of the recent studies that might reveal the biophysical bases of these stimulus-response phenomena.

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Section: Spatial Effects Of CI Stimulation Related To Temporal Interamentioning

confidence: 62%

Temporal Considerations for Stimulating Spiral Ganglion Neurons with Cochlear Implants

Boulet

White

Bruce

2015

JARO

103

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“…Both cathodic and anodic currents can initiate action potentials in extracellular auditory nerve stimulation (reviewed in Macherey et al 2008). Shepherd and Javel (1999) showed that when the second phase of a biphasic pulse is the excitatory one, the fiber response is delayed by the IPG duration as expected (see Fig.…”

Section: Inter-phase Gapmentioning

confidence: 64%

Auditory-Nerve Responses to Varied Inter-Phase Gap and Phase Duration of the Electric Pulse Stimulus as Predictors for Neuronal Degeneration

Ramekers

Versnel

Strahl

et al. 2014

JARO

153

268

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After severe hair cell loss, secondary degeneration of spiral ganglion cells (SGCs) is observed-a gradual process that spans years in humans but only takes weeks in guinea pigs. Being the target for cochlear implants (CIs), the physiological state of the SGCs is important for the effectiveness of a CI. For assessment of the nerve's state, focus has generally been on its response threshold. Our goal was to add a more detailed characterization of SGC functionality. To this end, the electrically evoked compound action potential (eCAP) was recorded in normal-hearing guinea pigs and guinea pigs that were deafened 2 or 6 weeks prior to the experiments. We evaluated changes in eCAP characteristics when the phase duration (PD) and inter-phase gap (IPG) of a biphasic current pulse were varied. We correlated the magnitude of these changes to quantified histological measures of neurodegeneration (SGC packing density and SGC size). The maximum eCAP amplitude, derived from the input-output function, decreased after deafening, and increased with both PD and IPG. The eCAP threshold did not change after deafening, and decreased with increasing PD and IPG. The dynamic range was wider for the 6-weeks-deaf animals than for the other two groups. Excitability increased with IPG (steeper slope of the input-output function and lower stimulation level at the half-maximum eCAP amplitude), but to a lesser extent for the deafened animals than for normal-hearing controls. The latency was shorter for the 6-weeks-deaf animals than for the other two groups. For several of these eCAP characteristics, the effect size of IPG correlated well with histological measures of degeneration, whereas effect size of PD did not. These correlations depend on the use of high current levels, which could limit clinical application. Nevertheless, their potential of these correlations towards assessment of the condition of the auditory nerve may be of great benefit to clinical diagnostics and prognosis in cochlear implant recipients.

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“…Contrary to most data obtained from animal and computer models (Frijns et al 1996;Miller et al 1997Miller et al , 1998Miller et al , 1999bMiller et al , 2001Klop et al 2004;Smit et al 2010), objective and behavioral data from CI users suggest that the anodic polarity is more effective than the cathodic one 2008Undurraga et al 2010Undurraga et al , 2012. However, there are several issues that shall be taken into account from those studies.…”

Section: Introductionmentioning

confidence: 89%

“…First, all behavioral data were obtained in the presence of a counteracting phase of opposite polarity 2008;. A number of studies have shown that thresholds decrease between 2 and 7.5 dB per doubling of phase width (PW) (Bonnet et al 2012;McKay and McDermott 1999;Miller et al 1999a;Moon et al 1993;Pfingst et al 1991;Prado-Guitierrez et al 2006;Shepherd and Javel 1999;Zeng et al 1998).…”

Section: Introductionmentioning

confidence: 99%

“…1). Macherey et al (2008) measured masking by anodic and cathodic phases of pseudomonophasic (PS) pulses with an inter-phase gap (IPG) of a symmetric (SYM) biphasic probe and found that the anodic phase produced more masking than the cathodic phase. However, it has been suggested that different polarities could excite different populations of AN fibers (Miller et al 1997;Ranck 1975).…”

Section: Introductionmentioning

confidence: 99%

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The Polarity Sensitivity of the Electrically Stimulated Human Auditory Nerve Measured at the Level of the Brainstem

Undurraga

Carlyon

Wouters

et al. 2013

JARO

Self Cite

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Recent behavioral studies have suggested that the human auditory nerve of cochlear implant (CI) users is mainly excited by the positive (anodic) polarity. Those findings were only obtained using asymmetric pseudomonophasic (PS) pulses where the effect of one phase was measured in the presence of a counteracting phase of opposite polarity, longer duration, and lower amplitude than the former phase. It was assumed that only the short high-amplitude phase was responsible for the excitation. Similarly, it has been shown that electrically evoked compound action potentials could only be obtained in response to the anodic phases of asymmetric pulses. Here, experiment 1 measured electrically evoked auditory brainstem responses to standard symmetric, PS, reversed pseudomonophasic, and reversed pseudomonophasic with inter-phase gap (6 ms) pulses presented for both polarities. Responses were time locked to the short high-amplitude phase of asymmetric pulses and were smaller, but still measurable, when that phase was cathodic than when it was anodic. This provides the first evidence that cathodic stimulation can excite the auditory system of human CI listeners and confirms that this stimulation is nevertheless less effective than for the anodic polarity. A second experiment studied the polarity sensitivity at different intensities by means of a loudness balancing task between pseudomonophasic anodic (PSA) and pseudomonophasic cathodic (PSC) stimuli. Previous studies had demonstrated greater sensitivity to anodic stimulation only for stimuli producing loud percepts. The results showed that PSC stimuli required higher amplitudes than PSA stimuli to reach the same loudness and that this held for current levels ranging from 10 to 100 % of the dynamic range.

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Higher Sensitivity of Human Auditory Nerve Fibers to Positive Electrical Currents

Cited by 107 publications

References 36 publications

Temporal Considerations for Stimulating Spiral Ganglion Neurons with Cochlear Implants

Temporal Considerations for Stimulating Spiral Ganglion Neurons with Cochlear Implants

Auditory-Nerve Responses to Varied Inter-Phase Gap and Phase Duration of the Electric Pulse Stimulus as Predictors for Neuronal Degeneration

The Polarity Sensitivity of the Electrically Stimulated Human Auditory Nerve Measured at the Level of the Brainstem

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