Figure 1.

Partial limbic seizures in pilocarpine-treated rats are associated with fast polyspike activity in the hippocampus and ictal neocortical slow activity in the frontal cortex. Spontaneous seizures are shown from chronic video/EEG recordings in rats with pilocarpine-induced epilepsy. A, LFPs in the hippocampus and orbitofrontal cortex (CTX) during a Racine class 0 partial seizure of 50 s length, associated with behavioral arrest but no convulsive activity. Hippocampal recordings reveal large-amplitude, fast polyspike activity during the seizure, whereas frontal recordings show large-amplitude 1–2 Hz slow waves during and after the seizure without considerable propagation of fast spike activity. Ictal and postictal slow activity resembles large-amplitude slow rhythms seen during an episode of natural sleep, recorded in the same animal at a different time (bottom, right). B, Hippocampal and frontal recordings during a 46 s Racine class 5 secondarily generalized seizure, associated with bilateral tonic-clonic convulsions and loss of balance. LFP recordings reveal large-amplitude, fast polyspike activity in both the hippocampus and frontal cortex during the seizure, without frontal slow oscillations. LFP recordings are filtered 0.3–100 Hz.