Caroline Jamison1, Steve J Aiken2, Michael Kiefte1, Aaron J Newman3, Manohar Bance4, Lauren Sculthorpe-Petley5. 1. School of Human Communication Disorders, Dalhousie University, Halifax, Nova Scotia, Canada. 2. School of Human Communication Disorders, Dalhousie University, Halifax, Nova Scotia, CanadaSchool of Psychology, Dalhousie University, Halifax, Nova Scotia, CanadaDivision of Otolaryngology, Queen Elizabeth II Health Sciences Centre, Halifax, Nova Scotia, Canada. 3. School of Psychology, Dalhousie University, Halifax, Nova Scotia, Canada. 4. School of Human Communication Disorders, Dalhousie University, Halifax, Nova Scotia, CanadaDivision of Otolaryngology, Queen Elizabeth II Health Sciences Centre, Halifax, Nova Scotia, Canada. 5. School of Human Communication Disorders, Dalhousie University, Halifax, Nova Scotia, CanadaSchool of Psychology, Dalhousie University, Halifax, Nova Scotia, CanadaDivision of Otolaryngology, Queen Elizabeth II Health Sciences Centre, Halifax, Nova Scotia, CanadaBiomedical Translational Imaging Centre, IWK Health Centre, Halifax, Nova Scotia, Canada.
Abstract
PURPOSE: Speech-in-noise testing relies on a number of factors beyond the auditory system, such as cognitive function, compliance, and motor function. It may be possible to avoid these limitations by using electroencephalography. The present study explored this possibility using the N400. METHOD: Eleven adults with typical hearing heard high-constraint sentences with congruent and incongruent terminal words in the presence of speech-shaped noise. Participants ignored all auditory stimulation and watched a video. The signal-to-noise ratio (SNR) was varied around each participant's behavioral threshold during electroencephalography recording. Speech was also heard in quiet. RESULTS: The amplitude of the N400 effect exhibited a nonlinear relationship with SNR. In the presence of background noise, amplitude decreased from high (+4 dB) to low (+1 dB) SNR but increased dramatically at threshold before decreasing again at subthreshold SNR (-2 dB). CONCLUSIONS: The SNR of speech in noise modulates the amplitude of the N400 effect to semantic anomalies in a nonlinear fashion. These results are the first to demonstrate modulation of the passively evoked N400 by SNR in speech-shaped noise and represent a first step toward the end goal of developing an N400-based physiological metric for speech-in-noise testing.
PURPOSE: Speech-in-noise testing relies on a number of factors beyond the auditory system, such as cognitive function, compliance, and motor function. It may be possible to avoid these limitations by using electroencephalography. The present study explored this possibility using the N400. METHOD: Eleven adults with typical hearing heard high-constraint sentences with congruent and incongruent terminal words in the presence of speech-shaped noise. Participants ignored all auditory stimulation and watched a video. The signal-to-noise ratio (SNR) was varied around each participant's behavioral threshold during electroencephalography recording. Speech was also heard in quiet. RESULTS: The amplitude of the N400 effect exhibited a nonlinear relationship with SNR. In the presence of background noise, amplitude decreased from high (+4 dB) to low (+1 dB) SNR but increased dramatically at threshold before decreasing again at subthreshold SNR (-2 dB). CONCLUSIONS: The SNR of speech in noise modulates the amplitude of the N400 effect to semantic anomalies in a nonlinear fashion. These results are the first to demonstrate modulation of the passively evoked N400 by SNR in speech-shaped noise and represent a first step toward the end goal of developing an N400-based physiological metric for speech-in-noise testing.