Interictal epileptiform discharges shape large-scale intercortical communication
Dynamic interactions between remote but functionally specialized brain regions enable complex information processing. This intercortical communication is disrupted in the neural networks of patients with focal epilepsy, and epileptic activity can exert widespread effects within the brain. Specifically, interictal epileptiform discharges (IEDs) identify epileptic brain regions and can impair memory, but the mechanisms by which they interact with physiological patterns of network activity are mostly undefined. Using large-scale human intracranial electroencephalography (iEEG) recordings and a rat model of temporal lobe epilepsy, we show that interictal epileptiform discharges (IEDs) are significantly coupled with spindles in discrete, individualized brain regions outside of the epileptic network. These IEDs are also associated with impaired memory consolidation. Brain regions that participate in this IED-driven oscillatory coupling express spindles that have a broader spatial extent and higher tendency to propagate than spindles occurring in uncoupled regions. Our findings suggest that IED-spindle coupling may be an important mechanism of interictal global network dysfunction that could be targeted to treat memory impairment in epilepsy.