Auditory brainstem's sensitivity to human voices.

Differentiating between voices is a basic social skill humans acquire early in life. The current study aimed to understand the subcortical mechanisms of voice processing by focusing on the two most important acoustical voice features: the fundamental frequency (F0) and harmonics. We measured frequency following responses in a group of young adults to a naturally produced speech syllable under two linguistic contexts: same-syllable and multiple-syllable. Compared to the same-syllable context, the multiple-syllable context contained more speech cues to aid voice processing. We analyzed the magnitude of the response to the F0 and harmonics between same-talker and multiple-talker conditions within each linguistic context. Results establish that the human auditory brainstem is sensitive to different talkers as shown by enhanced harmonic responses under the multiple-talker compared to the same-talker condition, when the stimulus stream contained multiple syllables. This study thus provides the first electrophysiological evidence of the auditory brainstem's sensitivity to human voices.