Abstract
Background and Purpose: The human supplementary motor area (SMA) contains two functional subregions of the SMA proper and preSMA; however, the reorganization patterns of the two SMA subregions after stroke remain uncertain. Meanwhile, a focal subcortical lesion may affect the overall functional reorganization of brain networks. We sought to identify the differential reorganization of the SMA subregions after subcortical stroke using the resting-state functional connectivity (rsFC) analysis.Methods: Resting-state functional MRI was conducted in 25 patients with chronic capsular stroke exhibiting well-recovered global motor function (Fugl–Meyer score >90). The SMA proper and preSMA were identified by the rsFC-based parcellation, and the rsFCs of each SMA subregion were compared between stroke patients and healthy controls.Results: Despite common rsFC with the fronto-insular cortex (FIC), the SMA proper and preSMA were mainly correlated with the sensorimotor areas and cognitive-related regions, respectively. In stroke patients, the SMA proper and preSMA exhibited completely different functional reorganization patterns: the former showed increased rsFCs with the primary sensorimotor area and caudal cingulate motor area (CMA) of the motor execution network, whereas the latter showed increased rsFC with the rostral CMA of the motor control network. Both of the two SMA subregions showed decreased rsFC with the FIC in stroke patients; the preSMA additionally showed decreased rsFC with the prefrontal cortex (PFC).Conclusion: Although both SMA subregions exhibit functional disconnection with the cognitive-related areas, the SMA proper is implicated in the functional reorganization within the motor execution network, whereas the preSMA is involved in the functional reorganization within the motor control network in stroke patients.
Highlights
The human supplementary motor area (SMA) consists of two functionally dissociated subregions (Klein et al, 2007; Nachev et al, 2008; Kim et al, 2010; Zhang et al, 2011)
Each region of interest (ROI) of the SMA and parcellated the SMA into anterior (preSMA) subregions was defined as a sphere centered at the averaged Montreal Neurological Institute (MNI) coordinate of the centroid of each subregion
Individual z-values were entered into a random effect one-sample ttest in a voxel-wise manner to identify brain regions that showed significant correlations with the seed ROI
Summary
The human supplementary motor area (SMA) consists of two functionally dissociated subregions (Klein et al, 2007; Nachev et al, 2008; Kim et al, 2010; Zhang et al, 2011). Previous studies have explored that the focal subcortical lesions can trigger remote effects on the function of brain networks after stroke (Dancause, 2006; Grefkes et al, 2008; Dubovik et al, 2012; Grefkes and Fink, 2014), which may account for various behavioral deficits, such as motor deficit (Wang et al, 2010), aphasia (de Boissezon et al, 2005; Choi et al, 2007), spatial neglect (He et al, 2007), cognitive impairment (Stebbins et al, 2008; Gottesman and Hillis, 2010), and so on. The human supplementary motor area (SMA) contains two functional subregions of the SMA proper and preSMA; the reorganization patterns of the two SMA subregions after stroke remain uncertain. We sought to identify the differential reorganization of the SMA subregions after subcortical stroke using the resting-state functional connectivity (rsFC) analysis
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