Altered Functional Organization Within And Between Resting-state Networks In Chronic Subcortical Infarction

Objective:This study aimed to perform ICA to investigate the changes in FC within each RSN and between RSNs in subcortical stroke patients who were well-recovered.Subjects and Methods:A total of25well-recovered patients (7females and18males) with a unilateral chronic ischemic infarct, involving of the internal capsule and neighboring regions were included.22age-matched healthy subjects (11females and11males) were also recruited as controls. Resting-state fMRI and structural images were acquired using a GE Signa HD-X3.0T scanner.1. The resting-state fMRI data were preprocessed using SPM8and DPARSF including slice timing, realignment, spatial normalization, resampling to3×3×3mm3voxels size, and smoothed with a6×6×6mm3full width at half maximum.2. RSNs were identified from fMRI data using the group ICA program of the fMRI toolbox.11RSNs were identified from the results of ICA. The group differences in the intra-network FC were investigated between the two groups with age and sex as covariates of no interest. And, each region of interest that showed significant group differences were extracted and compared between groups using a general linear model with the age and sex as covariates of no interest. Multiple comparisons were corrected using a Monte Carlo simulation.3. For the inter-network FC analysis, the preprocessing procedures were nearly the same as those for the ICA, except that the datasets were band-pass filtered, and several nuisance covariates were removed. First, Pearson correlation coefficients of the mean time courses between all pairs of RSNs were computed for each subject and then converted to z values using Fisher’s r-to-z transformation. Finally, the intergroup comparisons were performed with age and sex as covariates of no interest to analyze which pairs of internetwork FC reached significant differences.4. We performed partial correlation analysis to investigate the associations between the FC values (intra-and inter-network) and the lesion volume in stroke patients after controlling for age and sex (P<0.05).5. The same processing steps and statistical analyses were applied to the flipped and nonflipped data except that the ICA was separately run for the two sets of data.Results:1. The11RSNs were the ventral (vSMN) and dorsal (dSMN) SMNs, the occipital pole (pVN), the medial (mVN) and lateral (lVN) visual networks, the auditory network (AN), the dorsal attention network (DAN), the anterior (aDMN) and posterior (pDMN) DMNs, and the left (1FPN) and right (rFPN) FPNs.2. Stroke patients exhibited significantly increased intranetwork FC in the SMN, VN, AN, DAN, and pDMN. In contrast, stroke patients also exhibited significantly decreased intranetwork FC in the FPN and aDMN.3. Stroke patients shifted from no significant FC in controls to significant negative internetwork FC between the VN and AN as well as between the VN and SMN. Stroke patients also displayed weakened positive (aDMN and pDMN; pDMN and rFPN) or negative (AN and rFPN; pDMN and dSMN) internetwork FC4. We did not detect any significant correlations between the FC values and the lesion volume in stroke patients after controlling for age and sex, suggesting that lesion volume did not significantly influence our results.Conclusion:1. In chronic subcortical infarction patients, changes in FC were identified in multiple functional networks. And, the impairments and the compensation were coincided in the RSNs.2. Functional alterations in chronic subcortical infarction patients were present not only intranetwork but also internetwork.3. Analysis functional changes after stroke with large-scale brain networks, increased cognition complex clinical symptoms of subcortical infarction patients.