Figure 3.
Threshold for seizure initiation. A, Average [K+]o traces for perturbation durations ΔT = 5, 10, and 15 s (no pathological activity induced) and ΔT = 16, 17, 18, 19, 20 s (transition into pathological seizure state). B, Same as in A but with increased temporal resolution. C, Histograms of [K+]o at perturbation offset across the PY network (averaged over 2 s) for ΔT = 15 and 16 s (“no seizure” and “seizure”). D, Network with frozen [K+]o exhibited constant activity level during perturbation without transition to pathological activity state. E, Prolonged reduction of the afferent input triggered switch back to physiological state. Left, Color-coded PY activity map. Right, Sample PY membrane voltage trace (top) and corresponding [K+]o trace (bottom). Plots show alternating epochs of tonic firing and slow bursting interrupted by reduction in afferent input (indicated by vertical arrow). At the onset of the input reduction, the network switched to bursting and [K+]o returned back to baseline.