Mental Imitation and Mirroring in Children with Autism

Background: Although a deficit in imitation has been reported in autism spectrum disorders (ASD) (Williams et al., 2001; Rogers et al., 2003; 2008), recent studies have reported intact imitation skills in this disorder (Bird et al., 2007; Dinstein et al., 2010; Hamilton et al., 2007). Mental imitation, perhaps a precursor to motor imitation, involves visual perspective-taking and motor imagery (Jeannerod, 1994; Goldman, 2005). Research on mental imitation in autism has been rather limited compared to that on motor imitation. Considering the proposed role of impairments in the mirror mechanism and mentalizing ability in autism, we hypothesize that children with autism will have altered patterns of brain responses coupled with poorer task performance in mental imitation of actions.

Objectives: The main objective of this study is to determine the differences in brain responses underlying mirroring and mentalizing networks during mental imitation in children and adolescents with ASD 

Methods: Thirteen high-functioning children and adolescents with ASD and 16 age-and- IQ-matched typically developing (TD) control participants took part in this fMRI study. In the MRI scanner, participants were shown cartoon pictures of people performing everyday actions (Transitive actions: e.g., ironing clothes but with the hand missing; and Intransitive actions: e.g., clapping hands with the palms missing) and were asked to identify which hand or palm orientation (of three answer choices) would best fit the gap (Mozaz et al., 2002). Neuroimaging data was analyzed using AFNI and SPM12 to examine brain activation and functional connectivity. 

Results: The main findings of this study are as follows: 1) Processing both transitive and intransitive actions yielded activation in the bilateral inferior frontal gyrus (IFG) and inferior parietal lobule (IPL) in both ASD and TD groups; 2) Between-group analysis yielded hypoactivation in the ASD children, relative to TD, in the right angular gyrus and cerebellum for both conditions; 3) Hyperactivation in ASD, relative to the TD group, in the left middle occipital gyrus, left IFG, and IPL for both transitive and intransitive actions; and 4) whole-brain functional connectivity analysis revealed underconnectivity (ASD < TD) between the RIFG seed with left cerebellum, right insula, and the right fusiform gyrus and between the right IPL seed and right precentral gyrus (All analyses are reported at a statistical threshold of p < 0.05, cluster size k = 100; FWE corrected).

Conclusions: Increased activation in IFG and IPL in both groups suggests possible role of mirroring mechanism in mental imitation of actions. Hypoactivation in RIPL and its hypoconnectivity with motor areas in ASD suggest limited and/or altered engagement of the mirroring/motor network. This pattern of activation difference may have implications for understanding social movement and in social development through modeling in ASD. Hypoconnectivity of IFG with several regions also underscores the limited engagement of social brain areas in autism. Overall, our findings suggest that mirroring and mentalizing brain networks respond differently in children with ASD during tasks of mental imitation.