  Recent studies have shown that seizures can spread and terminate across brain
areas via a rich diversity of spatiotemporal patterns. In particular, while the
location of the seizure onset area is usually in-variant across seizures in a
same patient, the source of traveling (2-3 Hz) spike-and-wave discharges (SWDs)
during seizures can either move with the slower propagating ictal wavefront or
remain stationary at the seizure onset area. In addition, although most focal
seizures terminate quasi-synchronously across brain areas, some evolve into
distinct ictal clusters and terminate asynchronously. To provide a unifying
perspective on the observed diversity of spatiotemporal dynamics for seizure
spread and termination, we introduce here the Epileptor neural field model. Two
mechanisms play an essential role. First, while the slow ictal wavefront
propagates as a front in excitable neural media, the faster SWDs propagation
results from coupled-oscillator dynamics. Second, multiple time scales interact
during seizure spread, allowing for low-voltage fast-activity (>10 Hz) to
hamper seizure spread and for SWD propagation to affect the way a seizure
terminates. These dynamics, together with variations in short and long-range
connectivity strength, play a central role on seizure spread, maintenance and
termination. We demonstrate how Epileptor field models incorporating the above
mechanisms predict the previously reported diversity in seizure spread
patterns. Furthermore, we confirm the predictions for synchronous or
asynchronous (clustered) seizure termination in human seizures recorded via
stereotactic EEG. Our new insights into seizure spatiotemporal dynamics may
also contribute to the development of new closed-loop neuromodulation therapies
for focal epilepsy.
