title: Single- and multi-channel modulation detection in cochlear implant users.
abstract: Single-channel modulation detection thresholds (MDTs) have been shown to predict cochlear implant (CI) users' speech performance. However, little is known about multi-channel modulation sensitivity. Two factors likely contribute to multichannel modulation sensitivity: multichannel loudness summation and the across-site variance in single-channel MDTs. In this study, single- and multi-channel MDTs were measured in 9 CI users at relatively low and high presentation levels and modulation frequencies. Single-channel MDTs were measured at widely spaced electrode locations, and these same channels were used for the multichannel stimuli. Multichannel MDTs were measured twice, with and without adjustment for multichannel loudness summation (i.e., at the same loudness as for the single-channel MDTs or louder). Results showed that the effect of presentation level and modulation frequency were similar for single- and multi-channel MDTs. Multichannel MDTs were significantly poorer than single-channel MDTs when the current levels of the multichannel stimuli were reduced to match the loudness of the single-channel stimuli. This suggests that, at equal loudness, single-channel measures may over-estimate CI users' multichannel modulation sensitivity. At equal loudness, there was no significant correlation between the amount of multichannel loudness summation and the deficit in multichannel MDTs, relative to the average single-channel MDT. With no loudness compensation, multichannel MDTs were significantly better than the best single-channel MDT. The across-site variance in single-channel MDTs varied substantially across subjects. However, the across-site variance was not correlated with the multichannel advantage over the best single channel. This suggests that CI listeners combined envelope information across channels instead of attending to the best channel.
authors.affiliation: Division of Communication and Auditory Neuroscience, House Research Institute, Los Angeles, California, United States of America; Department of Head and Neck Surgery, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, United States of America; Department of Otorhinolaryngology, Head and Neck Surgery, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands; Research School of Behavioral and Cognitive Neurosciences, Graduate School of Medical Sciences, University of Groningen, Groningen, The Netherlands.
authors.forename: John J
authors.initials: JJ
authors.lastname: Galvin
authors.affiliation: Division of Communication and Auditory Neuroscience, House Research Institute, Los Angeles, California, United States of America; Department of Head and Neck Surgery, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, United States of America.
authors.forename: Sandy
authors.initials: S
authors.lastname: Oba
authors.affiliation: Division of Communication and Auditory Neuroscience, House Research Institute, Los Angeles, California, United States of America; Department of Head and Neck Surgery, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, United States of America.
authors.forename: Qian-Jie
authors.initials: QJ
authors.lastname: Fu
authors.affiliation: Department of Otorhinolaryngology, Head and Neck Surgery, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands; Research School of Behavioral and Cognitive Neurosciences, Graduate School of Medical Sciences, University of Groningen, Groningen, The Netherlands.
authors.forename: Deniz
authors.initials: D
authors.lastname: Başkent
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001309:Auditory Threshold; D003054:Cochlear Implants; D005260:Female; D006801:Humans; D008144:Loudness Perception; D008297:Male; D008875:Middle Aged