Observation of Goal-Directed Social Actions in Individuals with Autism Spectrum Disorders

Background:

The mirror neuron system (MNS), which becomes active during both action execution and action observation, is assumed to be involved in processing social information. Social communicative symptoms related to autism spectrum disorders (ASD) have been proposed to result from impairments in the MNS, however mixed results were found by previous studies.

Objectives:

To the best of our knowledge, this is the first study to compare modulations of MNS activity by the social relevance of observed actions in typically-developed young adults and in young adults with ASD.

Methods:

Participants
In the present study 20 individuals with an official diagnosis of ASD (M = 19.8 years) and 25 typically-developed (TD) individuals (M = 21.8 years) were included. ASD diagnoses were confirmed by administrating the ADOS-2 module 4.

Stimuli and procedure
Electroencephalography (EEG) recordings were obtained during the observation of video clips depicting two actors playing a simple card game governed by a set of rules, which were explained to the participants prior to the experiment. Four conditions that differed in social relevance were presented: dyadic, social, individual, and no action (baseline). Mu suppression, power reduction in the 8-13 Hz frequency band at the sensorimotor areas, was taken as index for MNS activity.

Results:

The TD group demonstrated significant mu suppression during the observation of the three types of actions and not during the observation of a still image. The degree of mu suppression was similar for the different action conditions, though increased mu suppression was found in the dyadic action condition compared to the social action condition. In contrast to the TD group, the ASD group did not show significant mu suppression during the observation of the three different actions. Due to the absence of mu suppression in all action conditions, no modulation by social relevance was detected.

Conclusions:

Based on the current findings it can be concluded that individuals with ASD might have a dysfunctional MNS, which contributes to our understanding of neurological impairments related to ASD. The indication that the MNS is not activated during the observation of both simple individual actions and more complex dyadic actions, suggests a global, rather than a specific, deficit of the MNS in individuals with ASD. The proposed link between ASD and a dysfunctional MNS could lead to new approaches for diagnosing and treating ASD. For example, therapy using imitation techniques could be an effective form of treatment in infants and children with ASD to stimulate the MNS at an early age.