Neurodevelopmental Trajectory of Emotional Attribution in Autism

Background:  The ability to interpret others’ body language is a vital skill that helps us infer their thoughts and emotions. However, individuals with autism have been found to have difficulty in understanding the meaning of people’s body language, perhaps leading to an overarching deficit in processing emotions (Moore et al., 1997; Hubert et al., 2007; Atkinson, 2009; Philip et al., 2010). There are only a few studies examining the neural bases of bodily emotions in autism (Grezes et al., 2009; Hadjikhani et al., 2009). The present study investigated the developmental trajectory of body-centered action and emotion in children and adults with autism. 

Objectives:  To investigate the neurodevelopmental changes underlying emotion and action, in the context of processing body language, in high-functioning children and adults with autism.  

Methods:  fMRI data was acquired from 17 children and 15 adults with high-functioning autism, and 16 children and 16 adults as typically developing controls, while they made emotion and action judgments about a series of static stick figure characters. The participants’ task was to view a character’s posture and choose the option, from three alternatives, that best described the action (e.g., pushing) or emotion (e.g., sad) the character was portraying. The stimuli were presented in a blocked design format and the data were acquired on a Siemens 3T scanner and analyzed using SPM8 and Group ICA Toolbox.

Results:  The main results are as follows: (1) Overall, processing body language activated bilateral inferior parietal lobule (IPL) and bilateral inferior frontal gyrus (IFG) (p=0.001, k=50). Activation in these areas became more robust moving from children to adults; (2) A simple regression using age as a covariate revealed a positive relationship between age and activation of left IFG, left postcentral, and left superior frontal cortex for judging emotional postures in participants with autism; (3) Comparing children with ASD to their TD peers, there was reduced activation in children with ASD in bilateral middle and inferior frontal cortex (p=0.005, k=20) while processing emotions; (4) An Independent Component Analysis revealed IPL, IFG, and medial prefrontal cortex (MPFC) as the primary component. Group comparison indicated significantly reduced coherence in RIPL, MPFC, and RIFG for the ASD participants compared to the control participants (p=0.005, k=50).

Conclusions:  The IFG and IPL are two main components of the human mirror neuron system (MNS) associated with the understanding of motor actions (Rizzolatti et al., 1996; Iacoboni et al., 1999).  All participants in our study engaged these regions while interpreting body language, indicating the possible use of a mirror mechanism to infer emotions from body postures. Reduced frontal cortex response in children with ASD may suggest a potential difference in the developmental trajectory of their frontal cortex. As participants with ASD increased in age, brain response in IFG and superior frontal areas increased. This may suggest a delay and/or deviance in development of the brain in ASD.