Simulations of monaural cochlear implants in normal hearing listeners have shown that the deleterious effects of upward spectral shifting on speech perception can be overcome with training. This study simulates bilateral stimulation with a unilateral spectral shift to investigate whether listeners can adapt to upward-shifted speech information presented together with contralateral unshifted information. A six-channel, dichotic, interleaved sine-carrier vocoder simulated a binaurally mismatched frequency-to-place map. Odd channels were presented to one ear with an upward frequency shift equivalent to 6 mm on the basilar membrane, while even channels were presented to the contralateral ear unshifted. In Experiment 1, listeners were trained for 5.3 h with either the binaurally mismatched processor or with just the shifted monaural bands. In Experiment 2, the duration of training was 10 h, and the trained condition alternated between those of Experiment 1. While listeners showed learning in both experiments, intelligibility with the binaurally mismatched processor never exceeded, intelligibility with just the three unshifted bands, suggesting that listeners did not benefit from combining the mismatched maps, even though there was clear scope to do so. Frequency-place map alignment may thus be of importance when optimizing bilateral devices of the type studied here.
Resistance to learning binaurally mismatched frequency-to-place maps: Implications for bilateral stimulation with cochlear implantsa)
Author to whom correspondence should be addressed. Present address: Audiology and Deafness Research Group, School of Psychological Sciences, University of Manchester, Manchester M13 9PL, United Kingdom. Electronic mail: sicilian@post.harvard.edu
Portions of this work were presented at the 2006 Midwinter Meeting of the Association for Research in Otolaryngology, the 2007 Conference on Implantable Auditory Prostheses, and the 2007 British Society of Audiologists Short Papers Meeting on Experimental Studies of Hearing and Deafness.
Catherine M. Siciliano, Andrew Faulkner, Stuart Rosen, Katharine Mair; Resistance to learning binaurally mismatched frequency-to-place maps: Implications for bilateral stimulation with cochlear implants. J. Acoust. Soc. Am. 1 March 2010; 127 (3): 1645–1660. https://doi.org/10.1121/1.3293002
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