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Background: Default mode network (DMN) is recognized to be involved in generation and propagation of epileptic activities in various epilepsies. Converging evidence has suggested disturbed functional connectivity (FC) in epilepsies, which was inferred to be related to underlying pathological mechanisms. However, abnormal changes of FC in DMN revealed by different studies are controversial, which obscures the role of DMN in distinct epilepsies. Objective: The present work aims to investigate the voxel-wise FC in DMN across epilepsies. Methods: A systematic review was conducted on 22 published articles before October 2020 indexed in PubMed and Web of Science. A meta-analysis with a random-effect model was performed using the effect-size signed differential mapping approach. Subgroup analyses were performed in three groups: idiopathic generalized epilepsy (IGE), mixed temporal lobe epilepsy (TLE), and mixed focal epilepsy (FE) with different foci. Results: The meta-analysis suggested common decreased FC in mesial prefrontal cortices across different epilepsies. Additional decreased FC in posterior DMN was observed in IGE. The TLE showed decreased FC in temporal lobe regions and increased FC in dorsal posterior cingulate cortex. Interestingly, an opposite finding in ventral and dorsal middle frontal gyrus was observed in TLE. The FE demonstrated increased FC in cuneus. Conclusion: The current findings revealed both common and specific alterations of FC in DMN across different epilepsies, highlighting the contribution of these dysfunctions to epileptic activities and cognitive behaviors in patients. Furthermore, the current study provided powerful evidence to support DMN as a potential candidate for effective intervention in epilepsy.

PurposeThe purpose of this study was to investigate the local spatiotemporal consistency of spontaneous brain activity in patients with frontal lobe epilepsy (FLE).MethodEyes closed resting‐state functional magnetic resonance imaging (fMRI) data were collected from 19 FLE patients and 19 age‐ and gender‐matched healthy controls. A novel measure, named FOur‐dimensional (spatiotemporal) Consistency of local neural Activities (FOCA) was used to assess the spatiotemporal consistency of local spontaneous activity (emphasizing both local temporal homogeneity and regional stability of brain activity states). Then, two‐sample t test was performed to detect the FOCA differences between two groups. Partial correlations between the FOCA values and durations of epilepsy were further analyzed.Key FindingsCompared with controls, FLE patients demonstrated increased FOCA in distant brain regions including the frontal and parietal cortices, as well as the basal ganglia. The decreased FOCA was located in the temporal cortex, posterior default model regions, and cerebellum. In addition, the FOCA measure was linked to the duration of epilepsy in basal ganglia.SignificanceOur study suggested that alterations of local spontaneous activity in frontoparietal cortex and basal ganglia was associated with the pathophysiology of FLE; and the abnormality in frontal and default model regions might account for the potential cognitive impairment in FLE. We also presumed that the FOCA measure had potential to provide important insights into understanding epilepsy such as FLE.

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