Resting-state FMRI Of Stroke With Motor Deficits

Motor dysfunction is a common sequela after stroke.In particular,motor impairments of the upper extremity and hands are very detrimental to the daily life of patients,seriously affecting the quality of patients' life.BOLD-fMRI has confirmed that subcortical stroke can lead to changes in cerebral plasticity away from the lesion,which is manifested as changes in cortical functional activities and functional reorganization.However,the relationship between the severity of motor dysfunction and changes of brain functional activitivies after subcortical stroke is still unclear.In this paper,granger causality analysis(GCA)and regional homogeneity(ReHo)of resting-state fMRI were applied to observe the altered effective connectivity and spontaneous neural activities in stroke with different severity of motor dysfunction,and further to explore the relationship between the abnormal neural activities and motor function scores.The study includes two parts as followed:(1)Altered effect connectivity of primary motor cortex in stroke with motor dysfunction The stroke survivors with different motor deficits(n=13,mild motor deficits;n=13,severe motor deficits,respectively)relative to healthy participants(n=13)were enrolled.Granger causality analysis(GCA)of resting-state fMRI data investigated the relationship between motor deficits and effective connectivity between the ipsilesional M1 and other brain regions.The results showed that compared with healthy controls,the influence from the ipsilesional M1 to contralateral sensorimotor cortices(SMC)decreased significantly in the severe motor deficits group,whereas,only the ipsilesional non-SMC involved in the mild motor deficits group;the influence to ipsilesional fronto-parietal network increased abnormally in the mild motor deficits group,whereas in the severe group,the effectivity connectivity increased only in the parietal lobe.In the opposite direction,the influences from bilateral frontal lobe to the ipsilesional M1 decreased,but from bilateral primary somatosensory cortex(S1),contralateral parietal lobule and visual cortex all increased in the severe stroke group;whereas,only the influence from the ipsilesional thalamus decreased in the mild stroke group.Compared with the severe stroke group,the mild stroke group showed decreased casual flow from the contralateral S1 and visual cortex to the ipsilesional M1,with their GCA values negatively correlated with the FMA scores(both the upper extremity section and the hand +wrist section of the Fugl–Meyer Scale).Our results indicated that the stroke patients displayed an abnormal effective connectivity network of the ipsilesional M1,which was related to the severity of upper limb motor dysfunction.These findings provided more valuable information for improving our understanding of the role of brain areas related to motor-execution and fronto-parietal motor control networks during brain plasticity following stroke,and provided reliable evidence and guidance for using appropriate clinical rehabilitation.(2)Abnormal regional homogeneity in stroke with motor dysfunction The same subjects as mentioned above were enrolled.The Kendall's concordance coefficients of the whole brain of each group was calculated.Two-sample t-test was performed to compare the differences in brain regions between the every two groups,and further investigate the relationship between motor deficits and ReHo of these areas.The results showed that compared with healthy controls,the ReHo in the ipsilesional caudate nucleus and thalamus decreased significantly,while the ReHo in the supplementary motor area and the contralesional inferior temporal gyrus,fusiform gyrus and cerebellum increased significantly in the mild stroke group.In the severe stroke group,the ReHo in the ipsilesional primary motor area,anterior cingulate gyrus,inferior temporal gyrus,insula,occipital middle gyrus and thalamus decreased significantly,but the ReHo in the contralesional superior frontal gyrus,inferior temporal gyrus and cerebellum increased significantly.Further comparison was made between the two subgroups of stroke.In the severe stroke survivors,the ReHo in the ipsilesional occipital gyrus and contralesional superior temporal gyrus were significantly lower than that in the mild motor stroke survivors,with their ReHo values positively correlated with the FMA scores(both the upper extremity section and the hand +wrist section of the Fugl–Meyer Scale).The results suggested that the abnormal resting brain function activity of unilateral subcortical stroke motor dysfunction mainly involved the subcortical regions adjacent to the lesion and the cerebral cortex far away from the lesion,which was closely related to the severity of motor dysfunction.ReHo in some brain regions were significantly correlated with patients' motor function scores,indicating that ReHo method may be used as an important reference for the assessment of motor dysfunction in stroke patients.