| Absence epilepsy can be regarded as a model for integrated, large-scale investigation of the emergence of pathological collective dynamics in the brain. Indeed, epileptic spike-wave discharges are thought to reflect abnormal cortical hypersynchronization. We explored the spatiotemporal dynamics of interactions within and between widely distributed cortical sites using magnetoencephalographic recordings of spontaneous absence seizures. We then extracted, from their time-frequency analysis, local synchronization of cortical sources and long-range synchronization linking distant sites. Our analyses revealed a reproducible sequence of 1) long-range desynchronization, 2) increased local synchronization and 3) increased long-range synchronization. Despite the differences in the spatio-temporal profiles of local and long-range synchronization, their cortical projections within an initiation time window overlap and reveal a multifocal fronto-central network. These observations question the classical view of sudden generalized synchronous activities in absence epilepsy. Furthermore, they suggest that brain states transition may rely on multi-scale processes involving both local and distant interactions. |
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