Fig. 1.

To assess the effects of interictal spikes on memory rats underwent intra-hippocampal pilocarpine injections to induced SE. Bilateral electrodes were placed in the ventral hippocampus (A). In the Delayed-Match-To-Sample test during the sample step, one of two levers is randomly presented (right or left) and is pressed by the rat (B). Then, in the Delay step, the rat has to poke its nose into a hole in the opposite wall for a random length of time (6–30 seconds). After this time period has elapsed, the first nosepoke into the hole turns off the stimulus light above and extends both levers. Then, in the Match step, the rat has to remember which lever he pressed during the sample phase, and press that same lever again to procure a food reward. During the sampling stage memory is encoded, during the delay phase memory is maintained, and during the match phase memory is retrieved. Performance is recorded for trials without spikes (C, top trace) and trials with spikes (C, bottom). Among trials in which an IIS occurs during the encoding or maintenance epoch of short-term memory, accuracy does not differ from trials without IIS (D). However, IISs during the retrieval phase produces a marked decrease in accuracy. Increasing delays produce decreases in accuracy, regardless of IIS epoch timing. Modified from Kleen et al., (Kleen et al., 2010) with permission. .