Author response image 1. Representative example of an epileptiform discharge recorded in the hippocampus in a freely moving animal (Tetanus Toxin injected in the hippocampus to create a focus).

The upper trace is in AC, the lower one is in DC. Note that the first AC “spike”, which would be qualified as “isolated interictal spike” is actually a very large DC shift. The second “spike” is part of an epileptic discharge. Note that AC filtering artificially shortens the true duration of the event. The large DC shift will eventually recover (not shown).