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Cortical specialization for non-speech and speech sounds in preterm and term neonates
Poster Session C, Thursday, October 1, 10:45 am - 12:45 pm, Wangari Maathai
Tian Hong1, Wenjie Jin2, Qinfen Zhang2; 1Shanghai Jiao Tong University, 2Changzhou Children’s Hospital of Nantong University
Early speech perception relies on auditory maturation and the emerging cortical organization of language-relevant sounds. However, it remains unclear how gestational maturity shapes neonatal responses to non-speech sounds and to different speech contrasts, including segmental and lexical tone contrasts. This study examined event-related potential responses to non-speech and speech sounds in 84 neonates, including 47 preterm and 37 full-term infants. In an auditory oddball paradigm, pure tones were used as non-speech stimuli, whereas Mandarin consonant and lexical tone contrasts were used as speech stimuli. EEG was recorded from 19 scalp electrodes. Mismatch responses were calculated from deviant-minus-standard difference waves, and a lateralization index was used to assess hemispheric asymmetry. Preterm neonates showed smaller mismatch responses than full-term neonates to pure tones, consonants, and lexical tones. For non-speech pure tones, neither group showed significant hemispheric lateralization. For speech sounds, full-term neonates showed left-lateralized responses to consonant contrasts and bilateral responses to Mandarin lexical tone contrasts, whereas preterm neonates showed no significant lateralization for either speech contrast. Gestational age was positively associated with cortical responses across sound types and with stronger left lateralization for consonant processing. Postmenstrual age was additionally associated with responses to lexical tone contrasts. These findings suggest that early cortical responses to sound vary across non-speech and speech domains. Whereas non-speech auditory discrimination appears bilaterally organized, segmental speech processing already shows left-hemisphere specialization in full-term neonates. The reduced responses and weaker lateralization observed in preterm neonates indicate that gestational maturation contributes to the emergence of speech-related cortical organization. By including Mandarin consonant and lexical tone contrasts, this study provides evidence from a tone language for the early neurobiological foundations of speech processing.
Topic Areas: Language Development/Acquisition, Speech Perception