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Using Interleaved Stimulation and EEG to Measure Temporal Smoothing and Growth of the Sustained Neural Response to Cochlear-Implant Stimulation
Authors:
GUERIT, F., DEEKS, J.M., Arzounian, D., Gransier, R., Wouters, J. & CARLYON, R.P.
Reference:
Journal of the Association for Research in Otolaryngology, 24(2):253-264
Year of publication:
2023
CBU number:
8882
Abstract:
Two EEG experiments measured the sustained neural response to amplitude-modulated (AM)
high-rate pulse trains presented to a single cochlear-implant (CI) electrode. Stimuli
consisted of two interleaved pulse trains with AM rates F1 and F2 close to 80 and 120 Hz
respectively, and where F2=1.5F1. Following Carlyon et al. (2021) we assume that such
stimuli can produce a Neural Distortion Response (NDR) at F0 = F2-F1 Hz if temporal
dependencies (“smoothing”) in the auditory system are followed by one or more neural
nonlinearities. In experiment 1 the rate of each pulse train was 480 pps and the gap between
pulses in the F1 and F2 pulse trains ranged from 0 to 984 μs. The NDR had a roughly constant
amplitude for gaps between 0 and about 200-400 μs, and decreased for longer gaps. We
argue that this result is consistent with a temporal dependency, such as facilitation,
operating at the level of the auditory nerve and/or with co-incidence detection by cochlearnucleus
neurons. Experiment 2 first measured the NDR for stimuli at each listener’s most
comfortable level (“MCL”) and for F0 = 37, 40, and 43 Hz. This revealed a group delay of
about 42 ms, consistent with a thalamic/cortical source. We then showed that the NDR grew
steeply with stimulus amplitude and, for most listeners, decreased by more than 12 dB
between MCL and 75% of the listener’s dynamic range. We argue that the NDR is a potentially
useful objective estimate of MCL.
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