Slow wave sleep is associated with forgetting in patients with temporal lobe epilepsy

While time spent in slow wave sleep (SWS) after learning promotes memory consolidation in the healthy brain, it is unclear if the same benefit is obtained in patients with temporal lobe epilepsy (TLE). Interictal epileptiform discharges (IEDs) are potentiated during SWS and thus may disrupt memory consolidation processes thought to depend on hippocampal-neocortical interactions. Here, we explored the relationship between SWS, IEDs, and overnight forgetting in patients with TLE. Nineteen patients with TLE studied object-scene pairs and memory was tested across a day of wakefulness (6 hrs) and across a night of sleep (16 hrs) while undergoing continuous scalp EEG monitoring. We found that time spent in SWS after learning was related to greater forgetting overnight. Longer duration in SWS and number of IEDs were each associated with greater forgetting, although the number of IEDs did not mediate the relationship between SWS and memory. Further research, particularly with intracranial recordings, is required to identify the mechanisms by which SWS and IEDs can be pathological to sleep-dependent memory consolidation in patients with TLE.