Aberrant interhemispheric functional reciprocities of the default mode network and motor network in subcortical ischemic stroke patients with motor impairment: A longitudinal study

Abstract

Purpose: The purpose of the present study was to explore the longitudinal changes in functional homotopy in the default mode network (DMN) and motor network and its relationships with clinical characteristics in patients with stroke.

Methods: Resting-state functional magnetic resonance imaging was performed in stroke patients with subcortical ischemic lesions and healthy controls. The voxel-mirrored homotopic connectivity (VMHC) method was used to examine the differences in functional homotopy in patients with stroke between the two time points. Support vector machine (SVM) and correlation analyses were also applied to investigate whether the detected significant changes in VMHC were the specific feature in patients with stroke.

Results: The patients with stroke had significantly lower VMHC in the DMN and motor-related regions than the controls, including in the precuneus, parahippocampus, precentral gyrus, supplementary motor area, and middle frontal gyrus. Longitudinal analysis revealed that the impaired VMHC of the superior precuneus showed a significant increase at the second time point, which was no longer significantly different from the controls. Between the two time points, the changes in VMHC in the superior precuneus were significantly correlated with the changes in clinical scores. SVM analysis revealed that the VMHC of the superior precuneus could be used to correctly identify the patients with stroke from the controls with a statistically significant accuracy of 81.25% (P ≤ 0.003).

Conclusions: Our findings indicated that the increased VMHC in the superior precuneus could be regarded as the neuroimaging manifestation of functional recovery. The significant correlation and the discriminative power in classification results might provide novel evidence to understand the neural mechanisms responsible for brain reorganization after stroke.

Keywords: functional homotopy; machine learning; resting-state functional magnetic resonance imaging; subcortical stroke; superior precuneus.

Figure 1

Lesion overlay map displaying regions of lesion overlap between participants. The n-value denotes the number of patients with a lesion in each voxel. L, left.

Figure 2

Regions showing significant changes in voxel-mirrored homotopic connectivity (VMHC) between each pair of the three groups. The threshold of the resulting statistical map was a combination of p < 0.005 for a single voxel and a minimum cluster size of 297 mm³.

Figure 3

The comparisons of VMHC between the three groups in the DMN and motor-related regions of interest. Bars represent the mean and error bars represent the standard deviations. SMA, supplementary motor area; MFG, middle frontal gyrus. Patients_pre = the patient group in the pretreatment stage. Patients_post = the patient group in the posttreatment stage. *, p < 0.05; **, p < 0.01; ***, p < 0.001.

Figure 4

The correlations between the changes in VMHC and the changes in clinical variables from the first timepoint and the second timepoint in the superior precuneus of stroke patients. (A) The correlation (r = 0.55, p = 0.03) between the changes of VMHC in superior precuneus and the changes of FMA. (B) The correlation (r = 0.72, p = 0.002) between the changes of VMHC in superior precuneus and the changes of NDS. (C) The correlation (r = −0.53, p = 0.04) between the changes of VMHC in SMA and the changes of NDS.

Figure 5

Classification plot (A) and receiver operating characteristic (ROC) curve (B) for the comparison between groups. Voxel-mirrored homotopic connectivity maps of 19 patients with stroke (pretreatment) and 13 healthy controls were used for classification, which yielded an accuracy of 81.25% (84.21% sensitivity, 76.92% specificity), which was statistically significant at p < 0.003.