# Action execution and observation in autistic adults: A systematic review of fMRI studies

## TL;DR

This study reviews fMRI findings in autistic adults during action execution and observation, showing similar brain regions are used as in neurotypical adults but with differences in activity levels.

## Contribution

The paper systematically reviews fMRI studies to identify atypical brain activation patterns in autistic adults during naturalistic actions.

## Key findings

- Autistic adults show similar brain regions as neurotypical adults during action execution and observation but with differences in activity direction and magnitude.
- Atypical recruitment of IFG, MTG, precentral, and parieto-occipital regions in ASD is linked to difficulties in motor planning and understanding others' actions.
- Brain activity overlaps suggest issues in movement planning and predictive control in autism.

## Abstract

Motor impairments are common in individuals with autism spectrum disorder (ASD) although less is known about the neural mechanisms related to such difficulties. This review provides an outline of functional magnetic resonance imaging (fMRI) findings associated with execution and observation of naturalistic actions in autistic adults. Summarized outcomes revealed that adults with ASD recruit similar brain regions as neurotypical adults during action execution and during action observation, although with a difference in direction and/or magnitude. For action execution, this included higher and lower activity bilaterally in the precentral cortex, the parietal cortex, the inferior frontal gyrus (IFG), the middle temporal gyrus (MTG), the occipital cortex, and the cerebellum. For action observation, differences mainly concerned both higher and lower activity in bilateral IFG and right precentral gyrus, and lower activity in MTG. Activity overlaps between action execution and observation highlight atypical recruitment of IFG, MTG, precentral, and parieto‐occipital regions in ASD. The results show atypical recruitment of brain regions subserving motor planning and/or predictive control in ASD. Atypical brain activations during action observation, and the pattern of activity overlaps, indicate an association with difficulties in understanding others' actions and intentions.

Movement difficulties are common in autistic individuals, possibly at least partly due to problems with planning the required motor activities to achieve an action goal and monitoring this motor plan during action. Problems with performing actions in autism may also be related to problems with understanding the action of others. One way to increase the understanding of movement problems in autism, and the particularities that may be related to such problems, is to explore what goes on in the brain during action performance. In this article, we present an overview of studies from the last 20 years that have used functional brain imaging to investigate brain activity during execution, observation, and imitation of naturalistic actions (i.e., ordinary motor behavior in the physical world) in autistic adults compared with neurotypical adults. Summarizing the various study results, we found that autistic adults mainly showed brain activity in similar brain areas as neurotypical adults, although differing in magnitude and/or direction (higher or lower activity). This indicates atypical engagement of brain regions that are important for action‐related activities, such as movement planning and performance and accessing prior experience of movement in autistic individuals. Given the frequency of movement problems in autism, it is therefore of importance to continue investigating how these problems relate to brain activity. This will help to establish a reliable scientific basis for clinical recommendations and interventions, and potentially add to the understanding of autism in general.