Objective: To determine whether auditory event-related potentials (ERPs) to a phonemic fricative contrast (“s” and “sh”) show significant differences in listening conditions with or without a hearing aid and whether the aided condition significantly alters a listener’s ERP responses to the fricative speech sounds.
Design: The raw EEG data were collected using a 64-channel system from 10 healthy adult subjects with normal hearing. The fricative stimuli were digitally edited versions of naturally produced syllables, /sa/ and /∫a/. The evoked responses were derived in unaided and aided conditions by using an alternating block design with a passive listening task. Peak latencies and amplitudes of the P1-N1-P2 components and the N1’ and P2’' peaks of the acoustic change complex (ACC) were analyzed.
Results: The evoked N1 and N1’ responses to the fricative sounds significantly differed in the unaided condition. The fricative contrast also elicited distinct N1-P2 responses in the aided condition. While the aided condition increased and delayed the N1 and ACC responses, significant differences in the P1-N1-P2 and ACC components were still observed, which would support fricative contrast perception at the cortical level.
Conclusion: Despite significant alterations in the ERP responses by the aided condition, normal-hearing adult listeners showed distinct neural coding patterns for the voiceless fricative contrast, “s” and “sh,” with or without a hearing aid.
This article describes how normal-hearing adult listeners neurally code the phonemic fricative contrast (“s” and “sh”) in cortical auditory event-related potentials in two listening conditions (with or without a hearing aid). While the aided listening condition increased and delayed the N1 and acoustic change complex responses, significant differences in the P1-N1-P2 and acoustic change complex components were still observed, which would support fricative contrast perception at the cortical level. Thus, despite significant alterations in the event-related potential responses by the aided condition, normal-hearing adult listeners showed distinct neural coding patterns for the voiceless fricative contrast with or without a hearing aid.
1Department of Speech-Language-Hearing Sciences, and 2Center for Neurobehavioral Development, University of Minnesota, Minneapolis, Minnesota, USA.
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This work was supported in part by Capita Foundation, Zhang Lab startup fund, the Graduate Research Partnership Program, and a Brain Imaging Research Award from the College of Liberal Arts, University of Minnesota.
The authors declare no other conflict of interest.
Address for correspondence: Yang Zhang, Department of Speech-Language-Hearing Sciences, 164 Pillsbury Drive SE, University of Minnesota, Minneapolis, MN 55455, USA. E-mail: firstname.lastname@example.org
Received March 6, 2013; accepted November 12, 2013.