Preattentive voice discrimination by the human brain as indexed by the mismatch negativity.

The goal of the present study was to determine whether the mismatch negativity (MMN), a component of the auditory event-related potential (ERPs) indexing perceptual difference between any two sounds, could be used as an objective measure of speaker discriminability and similarity/dissimilarity. ERPs were recorded in response to natural speech sounds from subjects watching a silent video. The stimuli consisted of a sequence of repetitive 'standard' sounds (the vowel /e/ pronounced by a female voice), which was infrequently interspersed with 'deviant' stimuli; the same /e/vowel pronounced by different speakers (one male and three females). Voice intensity and duration were matched between all the voices used. A separate behavioural discrimination task measured the perceptual distance of each deviant voice from the standard voice through pair-wise dissimilarity ratings. The MMN was elicited by all deviant voices. Furthermore, the dissimilarity ratings on the behavioural task paralleled the preattentive discrimination as indexed by the MMN amplitude. These results suggest that the MMN could be used as an objective measure of voice similarity/dissimilarity, and thus could serve objective speaker recognition.