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Cross-Modal Functional Connectivity of the Premotor Cortex Reflects Residual Motor Output After Stroke

Background Stroke is known to cause widespread activation and connectivity changes resulting in different levels of functional impairment. Recovery of motor functions is thought to rely mainly on reorganizations within the sensorimotor cortex but increasing attention is being paid to other cerebral regions Objective To investigate the motor task-related functional connectivity (FC) of the ipsilesional premotor cortex and its relation to residual motor output after stroke in poorly recovered patients. Methods 24 stroke patients with varying levels of motor deficits underwent functional magnetic resonance imaging while performing different motor tasks (passive mobilization, motor execution and motor imagery of an extension movement of the unaffected (UH) or paretic hand (AH). Task-related cerebral activation and seed-to-voxels FC of the ipsilesional lateral sensorimotor network (SMN) and particularly the premotor cortex (PMC) analyses were performed. Results Compared with movement of the UH, functional connectivity during movement of the AH was decreased between regions of the ipsilesional SMN and increased with regions of the frontal and the posterior parietal cortex such as the precuneus (Pcu). PMC FC during passive wrist mobilization with the contralesional SMN was negatively correlated with residual motor function whereas FC with non-motor regions such as the Pcu and the dorsolateral prefrontal cortex was positively correlated with the motor function. Conclusions Cross-modal FC of the ipsilesional PMC may reflect compensation strategies after stroke. The results emphasize the importance of the PMC and other non-motor regions as prominent nodes involved in reorganization processes after a stroke.