Article
Rate pitch discrimination with double pulse intervals optimized using ECAP responses
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Published: | November 28, 2019 |
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The rate pitch discrimination ability of cochlear implant (CI) users is poor compared to normal-hearing (NH) listeners. Already at low pulse rates, the just noticeable difference (JND) is on average about 20% of the base rate, while NH listeners can still discriminate small frequency differences of about 0.2% at 1 kHz.
A recent study investigated the application of double pulses with short interpulse intervals (IPIs) to improve temporal coding and therefore improve rate pitch discrimination. It was shown that double pulses with equal amplitudes have no significant effect on rate pitch discrimination.
Short IPIs, smaller than the absolute refractory period, result in a facilitation effect (first pulse reduces threshold for second pulse). The effect has its maximum if the amplitude of the first pulse is at or slightly below the ECAP threshold. The hypothesis is that double pulses with maximum facilitation improve temporal processing and therefore influences rate pitch discrimination.
Consequently, in our study, the amplitude of the first pulse was set at ECAP threshold, which was determined for each subject individually at one single apical electrode. The amplitude of the second pulse was increased until the pulse train was at most comfortable level. The rate pitch JND of this pulse train was determined for loudness balanced single and double pulses with 15 µs IPI. We will present first results but data collection is still ongoing.