Altered activity and information flow in the default mode network of pilocarpine-induced epilepsy rats

Temporal lobe epilepsy (TLE) is considered a brain activity disorder that is likely related to allomnesia and conscious disturbance. In rodents, TLE epileptiform discharges can be triggered by systemic administration of a dose of pilocarpine. However, how these pilocarpine-induced epileptiform discharges generate and propagate through the whole brain has not been well studied. In this study, we sought to assess alterations of activity and information flow in the default mode network (DMN) during TLE epileptiform discharges in pilocarpine-induced TLE rats. We identified that in resting state, the rat DMN could be divided into three subnetworks that constituted a frequency-specific information flow loop. This frequency-specific loop converted into frequency-independent flow patterns during the generation and propagation of epileptiform discharges. Moreover, the activity of the theta (4-8 Hz) and alpha (8-13 Hz) bands in each DMN subnetwork exhibited completely different alterations during epileptiform discharges. Overall, our results demonstrated frequency-dependent alterations of both activity and information flow patterns within the DMN during epileptiform discharge. These results suggest that the independence and cooperation of different frequency bands may serve as an underlying mechanism for the generation and propagation of epileptiform discharges in the brain during SE in pilocarpine-treated rats.