Figure 1
To assess the effects of interictal spikes on memory, rats underwent intra-hippocampal pilocarpine injections to induce SE. Bilateral electrodes were placed in the ventral hippocampus (A). In the delayed-match-to-sample memory 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 must 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 nose poke into the hole turns off the stimulus light above and extends both levers. Then, in the match step, the rat must remember which lever it 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 produce a marked decrease in accuracy. Increasing delays produces decreases in accuracy, regardless of IIS epoch timing. Modified from Kleen et al. (2010), with permission.