Perception-production link in infancy
Speech perception is multisensory from early in life. Pre-lingual infants match visual and auditory speech for both native (Patterson & Werker, 2003) and non-native (Danielson et al., 2017) speech suggesting that infants are sensitive to audio-visual speech without specific experience. Sensorimotor input also conveys speech-relevant information to the perceiver. Behavioural evidence shows that at 6-months, when the native phonological system is still being established, sensorimotor information influences speech perception in an articulator-specific manner (Bruderer et al., 2015; Choi et al., 2019). These studies suggest a potential link between speech perception and speech production systems that precedes active babbling. To further probe the relation between speech perception and production systems early on in ontogeny, the current study examines the neural dynamics underlying phonetic perception with and without articulator-specific oral-motor influences in 3-4 month olds. In this event-related-potential (ERP) design, neural responses to trials in which a single syllable is repeated (Standards) were compared to trials where the last syllable showed a phonetic category change following repetition (Deviants). In the auditory-only experiment, we tested discrimination of both English bilabial /ba/ vs. alveolar /da/, and non-native dental /da/ vs. retroflex /Da/. We identified a robust mismatch response (MMR) for both distinctions. In the auditory-motor experiment, infants participated in the same EEG task while their tongue-tip movement was restricted with a teething-toy. We observed an MMR only for the /ba/ and /da/ category change. These findings extend the previously reported behavioural results, providing electrophysiological evidence for articulator specific auditory-sensorimotor integration in pre-lingual infants.