Cortical processing of audiovisual speech perception in infancy and adulthood

The ability to detect auditory-visual correspondence in speech is an early hallmark of typical language development. Infants are able to detect audiovisual mismatches for spoken vowels such as /a/ and /i/ as early as 4 months of age. While adult event-related potential (ERP) data have shown an N300 associated with the detection of audiovisual incongruency in speech, it remains unclear whether similar responses can be elicited in infants. The present study collected ERP data in congruent and incongruent audiovisual presentation conditions for /a/ and /i/ from 21 typically developing infants (6~11 month of age) and 12 normal adults (18~45 years). The adult data replicated the N300 in the parietal electrode sites for detecting audiovisual incongruency in speech, and minimum norm estimation (MNE) showed the primary neural generator in the left superior temporal cortex for the N300. Unlike the adults, the infants showed a later N400 response in the centro-frontal electrode sites, and scalp topography as well as MNE results indicated bilateral activation in the temporal cortex with right-hemisphere dominance. Together, these data indicate important developmental changes in the timing and hemispheric laterality patterns for detecting audiovisual correspondence in speech.