ORCID Profile
0000-0002-8062-0837
Current Organisations
Technical University of Denmark
,
Danmarks Tekniske Universitet
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Publisher: AIP
Date: 2011
DOI: 10.1063/1.3658158
Publisher: Springer Science and Business Media LLC
Date: 24-08-2020
DOI: 10.1007/S10162-020-00767-Y
Abstract: The effect of the relative timing between pairs of same-polarity monophasic pulses has been studied extensively in single-neuron animal studies and has revealed fundamental properties of the neurons. For human cochlear implant listeners, the requirement to use charge-balanced stimulation and the typical use of symmetric, biphasic pulses limits such measures, because currents of opposite polarities interact at the level of the neural membrane. Here, we propose a paradigm to study same-polarity summation of currents while keeping the stimulation charge-balanced within a short time window. We used pairs of mirrored pseudo-monophasic pulses (a long-low phase followed by a short-high phase for the first pulse and a short-high phase followed by a long-low phase for the second pulse). We assumed that most of the excitation would stem from the two adjacent short-high phases, which had the same polarity. The inter-pulse interval between the short-high phases was varied from 0 to 345 μs. The inter-pulse interval had a significant effect on the perceived loudness, and this effect was consistent with both passive (membrane-related) and active (ion-channel-related) neuronal mechanisms contributing to facilitation. Furthermore, the effect of interval interacted with the polarity of the pulse pairs. At threshold, there was an effect of polarity, but, surprisingly, no effect of interval nor an interaction between the two factors. We discuss possible peripheral origins of these results.
Publisher: AIP
Date: 2011
DOI: 10.1063/1.3658090
Publisher: Acoustical Society of America (ASA)
Date: 11-2018
DOI: 10.1121/1.5070150
Abstract: The symmetric biphasic pulses used in contemporary cochlear implants (CIs) consist of both cathodic and anodic currents, which may stimulate different sites on spiral ganglion neurons and, potentially, interact with each other. The effect on the order of anodic and cathodic stimulation on loudness at short inter-pulse intervals (IPIs 0–800 μs) is investigated. Pairs of opposite-polarity pseudomonophasic (PS) pulses were used and the litude of each pulse was manipulated independently. In experiment 1 the two PS pulses differed in their current level in order to elicit the same loudness when presented separately. Six users of the Advanced Bionics CI (Valencia, CA) loudness-ranked trains of the pulse pairs using a midpoint-comparison procedure. Stimuli with anodic-leading polarity were louder than those with cathodic-leading polarity for IPIs shorter than 400 μs. This effect was small—about 0.3 dB—but consistent across listeners. When the same procedure was repeated with both PS pulses having the same current level (experiment 2), anodic-leading stimuli were still louder than cathodic-leading stimuli at very short intervals. However, when using symmetric biphasic pulses (experiment 3) the effect disappeared at short intervals and reversed at long intervals. Possible peripheral sources of such polarity interactions are discussed.
Publisher: Acoustical Society of America (ASA)
Date: 10-2017
DOI: 10.1121/1.5007757
Abstract: Up to medium intensities and in the 80–100-Hz region, the auditory steady-state response (ASSR) to a multi-tone carrier is commonly considered to be a linear sum of the dipoles from each tone specific ASSR generator. Here, this hypothesis was investigated when a unique modulation frequency is used for all carrier components. Listeners were presented with a co-modulated dual-frequency carrier (1 and 4 kHz), from which the modulator starting phase Φi of the 1-kHz component was systematically varied. The results support the hypothesis of a linear superposition of the dipoles originating from different frequency specific ASSR generators.
No related grants have been discovered for Bastian Epp.