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Level coding by phase duration and asymmetric pulse shape reduce channel interactions in cochlear implants

Quass, Gunnar Lennart ; Baumhoff, Peter ; Gnansia, Dan ; Stahl, Pierre ; Kral, Andrej

Hearing research, 2020-10, Vol.396, p.108070-108070, Article 108070 [Periódico revisado por pares]

Netherlands: Elsevier B.V

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  • Título:
    Level coding by phase duration and asymmetric pulse shape reduce channel interactions in cochlear implants
  • Autor: Quass, Gunnar Lennart ; Baumhoff, Peter ; Gnansia, Dan ; Stahl, Pierre ; Kral, Andrej
  • Assuntos: Channel interactions ; Cochlear implants ; Loudness coding ; Pulse symmetry ; Spread of excitation
  • É parte de: Hearing research, 2020-10, Vol.396, p.108070-108070, Article 108070
  • Notas: ObjectType-Article-1
    SourceType-Scholarly Journals-1
    ObjectType-Feature-2
    content type line 23
  • Descrição: •Asymmetric pulses reduce the spread of excitation compared to symmetric pulses.•Asymmetric pulses reduce channel interactions by up to 5%.•Phase-duration level coding amplifies this effect in the apical region. Conventional loudness coding with CIs by pulse current amplitude has a disadvantage: Increasing the stimulation current increases the spread of excitation in the auditory nerve, resulting in stronger channel interactions at high stimulation levels. These limit the number of effective information channels that a CI user can perceive. Stimulus intensity information (loudness) can alternatively be transmitted via pulse phase duration. We hypothesized that loudness coding by phase duration avoids the increase in the spread of the electric field and thus leads to less channel interactions at high stimulation levels. To avoid polarity effects, we combined this coding with pseudomonophasic stimuli. To test whether this affects the spread of excitation, 16 acutely deafened guinea pigs were implanted with CIs and neural activity from the inferior colliculus was recorded while stimulating with either biphasic, amplitude-coded pulses, or pseudomonophasic, duration- or amplitude-coded pulses. Pseudomonophasic stimuli combined with phase duration loudness coding reduced the lowest response thresholds and the spread of excitation. We investigated the channel interactions at suprathreshold levels by computing the phase-locking to a pulse train in the presence of an interacting pulse train on a different electrode on the CI. Pseudomonophasic pulses coupled with phase duration loudness coding reduced the interference by 4-5% compared to biphasic pulses, depending on the place of stimulation. This effect of pseudomonophasic stimuli was achieved with amplitude coding only in the basal cochlea, indicating a distance- or volume dependent effect. Our results show that pseudomonophasic, phase-duration-coded stimuli slightly reduce channel interactions, suggesting a potential benefit for speech understanding in humans.
  • Editor: Netherlands: Elsevier B.V
  • Idioma: Inglês
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  • Realização: ABCD-USP USP   Logos de Redes Sociais: Freepik

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