Altered spontaneous activity in the default-mode network and cognitive decline in chronic subcortical stroke

The resting-state functional connectivity (rsFC) has been reported to be impaired in the default-mode network (DMN) in stroke patients. However, it remains unclear whether the regional homogeneity (ReHo) of spontaneous activity and gray matter volume (GMV) are also altered in the DMN in these patients. Here we investigated ReHo, rsFC and GMV changes in the DMN and their functional correlations in stroke patients.

Eighteen patients with chronic subcortical stroke and 20 healthy controls underwent multi-modality MRI examinations to extract the DMN and to calculate the ReHo, rsFC and GMV. The ReHo difference in the DMN was compared between groups and brain regions with significant group differences in ReHo were extracted to calculate rsFC and GMV of these regions. Correlations of the cognitive or depressive scores with the imaging indices of the DMN that exhibit group differences were also investigated in stroke patients.

Compared with healthy controls, patients with stroke exhibited decreased ReHo in the posterior cingulate cortex (PCC) and decreased rsFC between the PCC and anterior cingulate cortex (ACC). There were no significant volumetric differences in the PCC or the whole DMN between the two groups. The ReHo (not the rsFC) of the PCC was correlated with cognitive decline even after controlling for depressive scores. Neither ReHo nor rsFC of the PCC was correlated with depressive severity in these patients.

These findings suggest that both regional spontaneous activity and their interactions are impaired in stroke patients and that the reduced ReHo of the PCC may underlie post-stroke cognitive decline.