A sensorimotor basis for facial expressivity differences in autism.

In autism, differences in the appearance, timing, and intensity of facial expressions are a major barrier to social communication. While disrupted sensorimotor feedback has been proposed as a potential contributing factor, the neural pathways linking sensory input to facial motor control are poorly understood even in the general population. In this study, we provide novel characterization of resting-state functional connectivity (rs-FC) between the facial regions of the primary somatosensory (S1) and motor (M1) cortices in both nonautistic and autistic individuals. We identify that rs-FC is somatotopically patterned for the lower but not upper face in both groups, mirroring known anatomical differences in corticomotor inputs to the upper versus lower face musculature. We independently replicate this patterning in a large, open-source neuroimaging dataset. Critically, we demonstrate that upper face actions are selectively diminished in autism, and that the relationship between sensorimotor connectivity and facial behavior diverges between autistic and nonautistic individuals. These findings offer the first direct evidence of a sensorimotor basis for altered facial expressivity in autism, challenging long-held assumptions about the underlying mechanisms of this communication barrier and pointing toward new targets for therapeutic intervention.