Neural encoding of speech-in-noise in neonates: A frequency-following response study.

Background noise disrupts the neural encoding of speech, making it particularly challenging to extract a speaker's voice from competing voices-an ability crucial for successful speech processing and communication. This disruption occurs across all ages, with infants and older adults being particularly vulnerable. In infancy, when robust speech encoding is fundamental for native language acquisition, the presence of background noise could have significant consequences for the development of speech and language processing. This study investigates the impact of background noise on the neural encoding of speech sounds in neonates. We recorded the frequency-following response to a /da/ syllable in both quiet and noise conditions from 25 healthy-term neonates and 21 normal-hearing adults. Results revealed higher neural responses in the adult group compared to newborns. Both groups exhibited reduced spectral amplitudes in the noise condition, with adults showing a greater decrease in the fundamental frequency spectral amplitude during the consonant transition compared to the steady vowel section. In contrast, neonates displayed similar disruption across both sections, possibly reflecting their immature auditory systems and limited exposure to higher-frequency formants in utero. This study represents a first step toward understanding the development of speech-in-noise processing from birth.