Figure 10. The effectiveness of optogenetic curtailment of seizure duration was determined by preceding brain state. A, For seizures that emerged from a non-theta state, the time-frequency spectrogram of hippocampal LFP before seizures did not show a clear band of power in the theta range (6–10 Hz). Vertical red line indicates seizure onset. B, Same as shown in A, but for a seizure that emerged from a theta state. Note the clear band of power at 7 Hz. C, In the intrahippocampal kainate model, 89.8% of analyzed seizures emerged from non-theta states (308 seizures, 4 animals) and 10.2% emerged from theta states (35 seizures, 4 animals). D, Optogenetic activation of PV interneurons successfully curtailed seizures that emerged from non-theta states. Seizure durations were shorter with light intervention (blue line, 154 seizures) than without light intervention (black line, 154 seizures; ***p <0.001, two-sample K-S test). E, Optogenetic activation of PV interneurons did not curtail seizures that emerged from theta states. Seizure durations with light intervention (blue line, 18 seizures) and without light intervention (gray line, 17 seizures) did not differ (n.s., two-sample K-S test). F, The durations of seizures emerging from theta states (with or without light intervention, blue and gray line redrawn from E did not differ from the durations of seizures emerging from non-theta states without light intervention (black line, redrawn from D).