Background:
Resting-state fMRI (rs-fMRI) has been used for assessing task-free brain activity changes after stroke. One prominent resting-state neural network is the default mode network (DMN) that has been suggested to be suppressed during cognitive tasks. Older adults often show difficulties in suppressing DMN compared to younger adults during cognitive task performance. Moreover, dysfunction of DMN appears to be linked with the severity of post-stroke depression. Here we explored brain plasticity changes in DMN in stroke subjects.
Methods:
9 stroke subjects (mean age=60.3, 5 Male) and 5 normal healthy subjects (mean age=48, 4 Male) underwent two rs-fMRI scans. Patients participated in the 1st scan within 7 days after onset and within 6 months (mean ~3 months) postonset in the 2nd scan. Brain plasticity changes were examined by functional connectivity measures that were computed using region-of-interest analysis. Rs-fMRI data were pre-processed in AFNI. The resulting time-series from 6 common seeds in DMN were averaged over each seed and correlated with that from every other seed to generate the Pearson correlation coefficients. These correlations were then z-transformed representing the 15 unique functional connections (fconn) in DMN. Fconn changes were determined with intraclass correlation (ICC), which measures reproducibility of fconn between scans. A reliable connection, as suggested to be an ICC ≥ 0.5, requires a small within-subject plasticity change compared to the between-subject variance.
Results:
Shown in Table 1.
Conclusion:
As seen from Table 1, fconn between RtLatPar and PC may undergo plasticity changes after stroke (ICC < 0.5) as would be reliable in the normal group. Fconn between LtLatPar and PC, mPFC and PC, right and left LatPar were found to be significant and reliable, which could be due to less suppression in DMN and higher between-subject variability after stroke.
Spontaneous Brain Activity in the Default Mode Network Is Sensitive to Different Resting-State Conditions with Limited Cognitive Load
