Neural and Kinematic Characteristics of Reaching in Autistic Children During Movement Observation, Execution, and Synchronization: An fNIRS Study

Background/Objectives: Children with Autism Spectrum Disorder (ASD, here on termed autistic children) exhibit motor difficulties in social and non-social contexts. Although previous studies have reported behavioral and neural characteristics, their relationship remains largely unexplored. The current study aimed to investigate the behavioral and neural mechanisms underlying interpersonal synchrony in autistic children using simultaneous kinematic and Functional Near-Infrared Spectroscopy (fNIRS) recordings. Methods: Fifty-eight autistic or non-autistic children participated (mean age = 10.1, standard error = 0.3). fNIRS and an inertial measurement unit were used simultaneously to record the neural activity over frontotemporal and parietal regions and arm movement kinematics during a reach-to-clean-up task across three conditions: Watch—the child observed the tester clean up the blocks; Do—the child cleaned up the blocks independently; and Together—the child and tester cleaned up the blocks synchronously. Results: Behaviorally, autistic children demonstrated longer movement displacement, higher average velocity and acceleration, and a greater number of movement units. In terms of cortical activation, autistic children showed hypoactivation in the bilateral precentral gyrus and right inferior parietal lobe, along with hyperactivation in the right middle frontal gyrus, left inferior frontal gyrus, and left inferior parietal lobule. Correlations between kinematic and neural measures suggest that autistic children rely more on online/feedback control to compensate for reduced feedforward control. Conclusions: This study reveals unique compensatory strategies in autistic children, highlighting the connections between neural and behavioral characteristics. These findings have strong potential to inform the development of ASD screening tools and to guide targeted intervention strategies.