title: Binaural unmasking with multiple adjacent masking electrodes in bilateral cochlear implant users.
abstract: Bilateral cochlear implant (BiCI) users gain an advantage in noisy situations from a second implant, but their bilateral performance falls short of normal hearing listeners. Channel interactions due to overlapping electrical fields between electrodes can impair speech perception, but its role in limiting binaural hearing performance has not been well characterized. To address the issue, binaural masking level differences (BMLD) for a 125 Hz tone in narrowband noise were measured using a pair of pitch-matched electrodes while simultaneously presenting the same masking noise to adjacent electrodes, representing a more realistic stimulation condition compared to prior studies that used only a single electrode pair. For five subjects, BMLDs averaged 8.9 ± 1.0 dB (mean ± s.e.) in single electrode pairs but dropped to 2.1 ± 0.4 dB when presenting noise on adjacent masking electrodes, demonstrating a negative impact of the additional maskers. Removing the masking noise from only the pitch-matched electrode pair not only lowered thresholds but also resulted in smaller BMLDs. The degree of channel interaction estimated from auditory nerve evoked potentials in three subjects was significantly and negatively correlated with BMLD. The data suggest that if the amount of channel interactions can be reduced, BiCI users may experience some performance improvements related to binaural hearing.
authors.affiliation: Department of Otolaryngology - Head and Neck Surgery, University of California, Irvine, California 92697, USA. telu@uci.edu
authors.forename: Thomas
authors.initials: T
authors.lastname: Lu
authors.forename: Ruth
authors.initials: R
authors.lastname: Litovsky
authors.forename: Fan-Gang
authors.initials: FG
authors.lastname: Zeng
mesh_terms: D000161:Acoustic Stimulation; D000368:Aged; D000704:Analysis of Variance; D001309:Auditory Threshold; D019929:Cochlear Implantation / Q000295:instrumentation*; D003054:Cochlear Implants; D012048:Correction of Hearing Impairment / Q000523:psychology; D004558:Electric Stimulation; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009622:Noise / Q000009:adverse effects*; D010470:Perceptual Masking; D019986:Persons with Hearing Disabilities / Q000523:psychology / Q000534:rehabilitation; D011474:Prosthesis Design; D011571:Psychoacoustics; D012815:Signal Processing, Computer-Assisted; D013067:Speech Perception