Preliminary Investigation of the Passively Evoked N400 as a Tool for Estimating Speech-in-Noise Thresholds.
OBJECTIVE
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.


METHODS
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.
School of Human Communication Disorders, Dalhousie University, Halifax, Nova Scotia, Canada.
Caroline
C
Jamison
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.
Steve J
SJ
Aiken
School of Human Communication Disorders, Dalhousie University, Halifax, Nova Scotia, Canada.
Michael
M
Kiefte
School of Psychology, Dalhousie University, Halifax, Nova Scotia, Canada.
Aaron J
AJ
Newman
School of Human Communication Disorders, Dalhousie University, Halifax, Nova Scotia, CanadaDivision of Otolaryngology, Queen Elizabeth II Health Sciences Centre, Halifax, Nova Scotia, Canada.
Manohar
M
Bance
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.
Lauren
L
Sculthorpe-Petley
D000161:Acoustic Stimulation; D000328:Adult; D004569:Electroencephalography; D005071:Evoked Potentials / Q000502:physiology; D005072:Evoked Potentials, Auditory / Q000502:physiology*; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D008297:Male; D009622:Noise; D059629:Signal-To-Noise Ratio; D013067:Speech Perception / Q000502:physiology*; D013069:Speech Reception Threshold Test; D055815:Young Adult