Increases in interneuron rate do not necessarily mean increases in inhibition. A looming question about the role of interneurons during seizures is whether they undergo depolarization block—in such cases interneurons would be functionally impotent as they would no longer fire action potentials despite being excited. It is also possible that sustained high rates would lead to synaptic rundown or postsynaptic depression of inhibitory outputs again rendering interneurons impotent (despite persisting to fire action potentials). To test whether any of this was going on, Miri et al did a smart experiment. They light-stimulated either PV+ or SST+ interneurons during baseline, preictal, and ictal periods to determine whether interneurons had a functional impact on principal cell activity during these different periods. If inhibition from either cell type was compromised due to either mechanism described above, stimulating interneurons via light would have little effect on principal cell activity. Inhibition was intact during all periods—stimulation always caused a reduction in firing rate of principal cells. This suggests that leading up to and during early phases of seizures, inhibition from these 2 interneuron types is functioning—the breaks are on. These results are consistent with other work showing that optogenetic activation of PV+ interneurons is capable of truncating spontaneous seizures in chronic epilepsy.6