Figure 1. Seizure Propagation Time Decreases During Epileptogenesis.

(A–D) Representative EEG traces from individual depth electrodes placed in the methionine sulfoximine (MSO)-infused (i.e., glutamine synthetase [GS]–inhibited, ipsilateral”hippocampus, left panels) and contralateral noninfused hippocampus (right panels) during early (A and B) and late (C and D) epileptogenesis. During early epileptogenesis, the seizure starts first in the ipsilateral hippocampus (red arrow in A) and appears next in the contralateral hippocampus (blue arrow) after a delay (propagation time) of 29 seconds (yellow highlight). Later in epileptogenesis, the seizure also starts in the GS-inhibited hippocampus (red arrow in C) followed by appearance in the contralateral hippocampus (blue arrow in D); however, the propagation time is much shorter (2 seconds, purple highlight). The time of the initiation and end of the propagation time is marked above the blue and red arrows. (E and F) Analysis of a total of 78 spontaneous seizures combined from the MSO-infused rats implanted with depth electrodes (n = 3) shows a statistically significant decrease in propagation time from early (11.65 seconds) to late (6.82 seconds, p = 0.02) epileptogenesis. Each EEG trace shows 240 seconds of continuous (long-string) data. The scale on the y-axis is from −4 to +4 mV, and the light vertical lines demarcate each second of the EEG.