DisorderDexterity and fronto-parietal networks in Autism

Background: Fine motor skill impairments are common in Autism Spectrum Disorder (ASD), significantly impacting quality of life. Sensory inputs reaching the primary motor cortex (M1) from the somatosensory cortex (S1) are likely involved in fine motor skill, and specifically motor learning. However, the role of these connections has not been directly investigated in humans. This study aimed to investigate, for the first time, the role of the S1-M1 connections in healthy controls in vivo, and whether microstructural alterations are associated with motor impairment in ASD. Methods: 60 right-handed neurotypical adult males aged 18-45, and 60 right-handed ageand sexmatched subjects diagnosed with ASD underwent fine motor skill assessment and scanning with diffusion tensor imaging (DTI). The streamlines of the hand region connecting S1-M1 of the motor-sensory homunculus were virtually dissected using TrackVis, and diffusion properties extracted. The face/tongue region connections were used as control tracts. Results: The ASD group displayed lower motor performances and altered DTI measurements of the hand-region connection. Behavioral performance correlated with hand-region DTI measures in both groups, but not with the face/tongue connections, indicating anatomical specificity. There was a lefthemisphere association of motor ability in the control group, and an atypical rightward shift in the ASD group. Conclusions: These findings suggest that direct interaction between S1 and M1 may contribute to the human ability to precisely interact with and manipulate the environment. As electrophysiological evidence indicates these connections may underpin long-term potentiation in M1, our findings may lead to novel therapeutic treatments for motor skill disorders.