Hemispheric Asymmetry of Supplementary Motor Area Proper: A Functional Connectivity Study of the Motor Network

Cerebral asymmetry is a common feature of human functions. However, there are discrepancies in the literature about functional hemispheric asymmetries in the supplementary motor area (SMA), specifically in the posterior part (SMA-proper). We used resting state functional connectivity MRI to investigate the left-right asymmetries of the functional networks associated with primary motor cortex (M1) and SMA-proper using a "seed"-based correlation analysis in 30 healthy right-handed subjects. We showed that left M1 was more connected with areas involved in the motor system than right M1, and that right SMA-proper had more functional connections than its left counterpart. Our results are in agreement with a leftward asymmetry for M1 connectivity, whereas there is a rightward asymmetry of the SMA-proper connectivity.