Neural correlates of social motor coordination in autism: A systematic review and meta-analysis of fNIRS studies

This study aimed to provide a comprehensive overview of how individuals with autism spectrum condition (ASC) process social motor coordination, focusing on joint action and its neural correlates, as examined through functional near-infrared spectroscopy (fNIRS) in comparing to their neurotypical (NT) counterparts. Eleven studies were analyzed, with nine included in the meta-analysis. The results identified the inferior parietal lobule (IPL) and superior temporal sulcus (STS) as significant moderators explaining group differences in cortical activation during joint action. Specifically, individuals with ASC showed increased IPL activation and reduced STS activation, indicating a greater reliance on kinematic processing and diminished engagement in encoding and integrating socially relevant information. Although the pooled effect size for inter-brain synchrony (IBS) was not statistically significant, descriptive analyses showed a trend toward reduced reciprocal processing in ASC, particularly in predicting and aligning with a partner's mental states, as supported by decreased IBS in the temporoparietal junction (TPJ). Furthermore, a visual inspection of behavioral and neural outcomes by autism severity exhibited distinct tendencies. Individuals with mild symptoms demonstrated different neural-behavioral associations compared to those with moderate-to-severe symptoms, suggesting that symptom severity influences how neural processing supports joint action. These findings highlight the differential involvement of neural systems in joint actions among individuals with ASC depending on task type and autism severity, and emphasize the distinction between intra- and inter-personal processing. By integrating these findings, this study offers a more integrative perspective on social motor coordination in ASC as a complex, multi-dimensional process.