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Proceedings Paper

Stochastic resonance in temporal processing by cochlear implant listeners
Author(s): Monita Chatterjee; Mark E Robert
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Paper Abstract

Cochlear implants (CI) provide speech information to the hearing-impaired by transmitting temporal information from specific frequency bands to corresponding regions of the tonotopically organized auditory system via electrical stimulation. We are interested in the role of applied noise in temporal coding by CI listeners. We measured sensitivity to sinusoidal amplitude modulation in adult users of the Nucleus-22 cochlear implant. The carrier was a train of current pulses presented at various amplitudes within the subject's dynamic range, driving a single electrode pair in the middle of the implanted electrode array. Consistent with previous findings, modulation sensitivity in CI listeners was positively related to carrier level. Introducing uniformly distributed, pseudorandom noise into the carrier envelope produced level-dependent effects. At high levels, modulation sensitivity decreased with increasing noise. At less sensitive low carrier levels, modulation sensitivity showed a stochastic resonance (SR) signature with increasing noise, displaying maximum sensitivity at an optimal noise level. This finding was also consistent with previous work. In a new experiment, we tested two new ways of degrading modulation sensitivity without changing carrier level: (1) by increasing modulation frequency and (2) by introducing a concurrent, fluctuating masker on another channel. Under each of these two conditions, our results show that increasing noise in the signal carrier envelope improved sensitivity in a manner consistent with SR. These results suggest that conditions that weaken modulation sensitivity strengthen the potential for SR. We speculate that the effect arises at a relatively central stage of temporal processing in the auditory system.

Paper Details

Date Published: 30 April 2003
PDF: 8 pages
Proc. SPIE 5110, Fluctuations and Noise in Biological, Biophysical, and Biomedical Systems, (30 April 2003); doi: 10.1117/12.499216
Show Author Affiliations
Monita Chatterjee, House Ear Institute (United States)
Mark E Robert, House Ear Institute (United States)


Published in SPIE Proceedings Vol. 5110:
Fluctuations and Noise in Biological, Biophysical, and Biomedical Systems
Sergey M. Bezrukov; Hans Frauenfelder; Frank Moss, Editor(s)

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