The Effects of Decreased Audibility Produced by High-Pass Noise Masking on N1 and the Mismatch Negativity to Speech Sounds /ba/ and /da/ This study investigated the effects of decreased audibility produced by high-pass noise masking on the cortical event-related potentials (ERPs) N1 and mismatch negativity (MMN) to the speech sounds /ba/ and /da/, presented at 65 dB SPL. ERPs were recorded while normal listeners (N=11) ignored the stimuli and read a book. ... Research Article
Research Article  |   April 01, 1999
The Effects of Decreased Audibility Produced by High-Pass Noise Masking on N1 and the Mismatch Negativity to Speech Sounds /ba/ and /da/
 
Author Affiliations & Notes
  • Brett A. Martin
    Auditory Evoked Potential Research Laboratory Albert Einstein College of Medicine Bronx, New York
    Program in Speech Hearing Sciences City University of New York
  • Diane Kurtzberg
    Departments of Neuroscience and Neurology Albert Einstein College of Medicine Bronx, New York
  • David R. Stapells
    School of Audiology and Speech Sciences University of British Columbia Vancouver Canada
  • Contact author: David R. Stapells, School of Audiology and Speech Sciences, University of British Columbia, 5804 Fairview Ave., Vancouver, BC, Canada V6T 1Z3.
    Contact author: David R. Stapells, School of Audiology and Speech Sciences, University of British Columbia, 5804 Fairview Ave., Vancouver, BC, Canada V6T 1Z3.×
  • Corresponding author: E-mail: stapells@audiospeech.ubc.ca
Article Information
Hearing & Speech Perception / Acoustics / Hearing Disorders / Speech, Voice & Prosody / Hearing / Research Articles
Research Article   |   April 01, 1999
The Effects of Decreased Audibility Produced by High-Pass Noise Masking on N1 and the Mismatch Negativity to Speech Sounds /ba/ and /da/
Journal of Speech, Language, and Hearing Research, April 1999, Vol. 42, 271-286. doi:10.1044/jslhr.4202.271
History: Received November 13, 1997 , Accepted October 28, 1998
 
Journal of Speech, Language, and Hearing Research, April 1999, Vol. 42, 271-286. doi:10.1044/jslhr.4202.271
History: Received November 13, 1997; Accepted October 28, 1998

This study investigated the effects of decreased audibility produced by high-pass noise masking on the cortical event-related potentials (ERPs) N1 and mismatch negativity (MMN) to the speech sounds /ba/ and /da/, presented at 65 dB SPL. ERPs were recorded while normal listeners (N=11) ignored the stimuli and read a book. Broadband masking noise was simultaneously presented at an intensity sufficient to mask the response to the speech sounds, and subsequently high-pass filtered. The conditions were QUIET (no noise); high-pass cutoff frequencies of 4000, 2000, 1000, 500, and 250 Hz; and broadband noise. Behavioral measures of discrimination of the speech sounds (d' and reaction time) were obtained separately from the ERPs for each listener and condition. As the cutoff frequency of the high-pass masker was lowered, ERP latencies increased and amplitudes decreased. The cutoff frequency where changes first occurred differed for N1 and MMN. N1 showed small systematic changes across frequency beginning with the 4000-Hz high-pass noise. MMN and behavioral measures showed large changes that occurred at approximately 1000 Hz. These results indicate that decreased audibility, resulting from the masking, affects N1 and the MMN in a differential manner. N1 reflects the presence of audible stimulus energy, being present in all conditions where stimuli were audible, whether or not they were discriminable. The MMN is present only for those conditions where stimuli were behaviorally discriminable. These studies of cortical ERPs in high/pass noise studies provide insight into the changes in brain processes and behavioral performance that occur when audibility is reduced, as in hearing loss.

Acknowledgments
This work was carried out at the Albert Einstein College of Medicine with support from the USPHS, NIDCD, and NICHD. Brett Martin was partially supported by an American Speech and Hearing Foundation Student Research Grant in Audiology (1992). This work is based on Brett Martin's doctoral dissertation. Portions of this work were presented at the Fourteenth International Symposium of the International Evoked Response Audiometry Study Group, Lyon, France, August 30, 1995. Larry Raphael, PhD, provided helpful comments on speech science aspects of this work.
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