Contribution of the resting-state functional connectivity of the contralesional primary sensorimotor cortex to motor recovery after subcortical stroke

Abstract

It remains uncertain if the contralesional primary sensorimotor cortex (CL_PSMC) contributes to motor recovery after stroke. Here we investigated longitudinal changes in the resting-state functional connectivity (rsFC) of the CL_PSMC and their association with motor recovery. Thirteen patients who had experienced subcortical stroke underwent a series of resting-state fMRI and clinical assessments over a period of 1 year at 5 time points, i.e., within the first week, at 2 weeks, 1 month, 3 months, and 1 year after stroke onset. Thirteen age- and gender-matched healthy subjects were recruited as controls. The CL_PSMC was defined as a region centered at the voxel that had greatest activation during hand motion task. The dynamic changes in the rsFCs of the CL_PSMC within the whole brain were evaluated and correlated with the Motricity Index (MI) scores. Compared with healthy controls, the rsFCs of the CL_PSMC with the bilateral PSMC were initially decreased, then gradually increased, and finally restored to the normal level 1 year later. Moreover, the dynamic change in the inter-hemispheric rsFC between the bilateral PSMC in these patients was positively correlated with the MI scores. However, the intra-hemispheric rsFC of the CL_PSMC was not correlated with the MI scores. This study shows dynamic changes in the rsFCs of the CL_PSMC after stroke and suggests that the increased inter-hemispheric rsFC between the bilateral PSMC may facilitate motor recovery in stroke patients. However, generalization of our findings is limited by the small sample size of our study and needs to be confirmed.

Figure 1. Lesion locations of stroke patients.

The lesions are shown on axial slices of the T2-weighted images. Patient numbers correspond with those in Table 1. L, left and R, right.

Figure 2. The BOLD response evoked by hand-grasping task.

Red-yellow areas show activation of the right PSMC acquired by the left hand-grasping task of 11 normal controls, and the blue area indicates the seed region of the CL_PSMC. BOLD, blood oxygen level dependent; CL, contralesional hemisphere; L, left; PSMC, primary sensorimotor cortex; and R, right.

Figure 3. The resting-state functional connectivity patterns of the CL_PSMC.

(A) Normal controls. (B) Stroke patients. CL, contralesional hemisphere; IL, ipsilesional hemisphere; L, left; PSMC, primary sensorimotor cortex; and R, right.

Figure 4. Post-stroke recovery curves of stroke patients.

The x-axis denotes days after stroke onset; and the y-axis denotes MI scores (ranging from 0 to 100, 100 represents complete recovery). MI, motricity index.

Figure 5. The changes in rsFC of the CL_PSMC.

Brain regions show increased rsFCs with the CL_PSMC after stroke in the ipsilesional (A) and contralesional hemispheres (B). (C) and (D) show group comparisons of inter-hemispheric and intra-hemispheric rsFC of healthy subjects and patients at 5 time points. Bars represent the means, error bars represent the SDs, and stars represent the significant differences between groups. NC, normal control; TP, time points; CL, contralesional hemisphere; IL, ipsilesional hemisphere; PSMC, primary sensorimotor cortex; and rsFC, resting-state functional connectivity.

Figure 6. Correlation between the inter-hemispheric rsFC of the PSMC and MI scores after stroke.

The x-axis represents MI scores at each time point after stroke, and the y-axis denotes the rsFC of the bilateral PSMC. CL, contralesional hemisphere; IL, ipsilesional hemisphere; MI, motricity index; PSMC, primary sensorimotor cortex; and rsFC, resting-state functional connectivity.