Reduced Neural Activity of Social and Motor Networks in Children and Adolescents with Autism Spectrum Disorder and Developmental Coordination Disorder during Observation and Imitation of Social and Motor Actions

Background: A growing body of literature suggests that children with ASD often have motor deficits and that these deficits may be related to social skills in ASD (Dziuk, 2007). Previous imaging work has shown that motor system networks (e.g., Action Observation Network [AON]) play a role in supporting intention understanding as well as imitation (Iacoboni, 2005). It is thus possible that mechanisms underlying motor impairments contribute to social deficits in ASD. To our knowledge, no study to date has investigated social and motor neural processing in ASD across a spectrum of social-motor stimuli nor has anyone compared such stimuli to clinical populations with motor impairments.

Objectives: (1) To assess how children and adolescents with ASD differ in social neural networks when observing and imitating social and motor stimuli compared to typically developing (TD) participants and individuals with developmental coordination disorder (DCD). (2) To assess how these differences may be related to group differences in social and motor skills assessed with the Social Responsiveness Scale (SRS; Constantino, 2003) and Movement Assessment Battery for Children (MABC-2; Henderson, 2007).

Methods: Data from thirteen high-functioning children and adolescents with ASD (mean age [years] 11.26±1.09), seven children and adolescents with DCD (mean age [years] 11.97±2.09), and sixteen TD participants (mean age [years] 11.25±1.41) were analyzed. Imaging data was collected on a 3-T Siemens MAGNETOM Prisma scanner. In the scanner, participants observed and imitated separately to three video stimuli conditions: 1) emotional expressions (i.e., Happy), 2) Non-Emotional expressions (i.e., wiggle nose) and 3) hand actions (i.e., cutting paper). Using a block design, each condition was randomly presented for 15-seconds followed by 15-seconds of rest. Standard preprocessing and motion scrubbing were performed. Direct whole brain comparisons between groups were made. The degree of social and motor skills were also analyzed to determine group differences in ability.

Results: During the observation task, the ASD group elicited less activation in social and motor regions (angular gyrus, amygdala) when observing emotional faces and increased activity when observing hand actions compared to TD participants. During the imitation task, TD participants showed increase activation in the left IFG when imitating emotional faces compared to the ASD group (p=.021), and when imitating hand condition compared to DCD (p=.022). Movement scores were significantly related to activity in motor regions (IFG) during the imitation task across groups (R=.405, p=.019). For children with ASD, activity in motor regions (inferior frontal gyrus) was also correlated with social ability (p<.05).

Conclusions: Our results indicate that motor regions are less active in ASD during observation and imitation. During imitation, activity in motor regions (inferior frontal gyrys) correlates with motor ability (MABC2 scores) across groups, and for social ability in the ASD group. These results may have implications for understanding heterogeneity within ASD along the axis of motor impairment, and in the long run, lead to individualized forms of treatment.