Differential lateralization to faces in infants at risk of autism spectrum disorder with expressive language delay

Face-to-face communication between caregiver and infant is essential for the development of language and social skills in infancy. A previous study on brain response toward human faces showed that a lateralization right fusiform gyrus (FG) response when viewing faces was associated with better social skills. However, the relationship, between infant face processing and language development remains unclear. This study aimed to examine whether brain responses to faces vary based on the ability level of language expression.

Overall, 42 Japanese infants (aged 18-34 months, Mean of age (Mage) = 24.7 months, standard deviation (SD) = 4.57, 47% female) were assessed for expressive communication skills and classified into two groups: a delayed group (20 infants) and a control group (infants with typical expressive language development, 22 infants). Brain activity was recorded using a child-customized magnetoencephalography during presentation of a mother's face, a stranger's face, and a nonface (scrambled image). The lateralization index of the FG during face viewing was calculated using the following formula: (L - R)/(L + R).

The results showed a significant difference in the lateralization index between the delayed and control groups. The control group showed rightward dominance of the FG activity when viewing the mother's face and others' faces, whereas the delayed group did not exhibit this lateralization. Based on behavioral observations, 75% of the delayed group met the criteria of autism spectrum disorder (ASD) risk, and infants with a high risk of ASD who had poor expressive language showed poor right hemispheric dominance compared to the control group in their brain responses to their mothers' faces.

This study suggests that lateralization of face processing in infancy may be a predictor of expressive language abilities.