Isabelle Lambert, MD: Spike, Spindle Frequency in Hippocampus During NREM Affect Long-Term Memory

October 22, 2018

Impairment of physiological spindle activity in the hippocampus during NREM sleep by interictal epileptic activities may have negative consequences on long-term memory consolidation.

“This suggests that the interictal spikes interrupt, maybe, this hippocampal neocortical transfer that is supposed to occur during NREM sleep, thanks to specific oscillations that are slow waves, sleep spindles and hippocampal ripples."

At the 24th Congress of the European Sleep Research Society, NeurologyLive spoke with Isabelle Lambert, MD, Sleep Unit, Clinical Neurophysiology, Timone Hospital, to discuss the results of a study that examined the effect of epileptic activities on physiological sleep activities in the hippocampus, and the consequences on long-term memory with intracranial EEG recordings.

The results revealed a negative correlation between spike frequency and spindle frequency in the hippocampus, as reported in previous works. There was, however, a significant correlation between spike frequency during the first cycle of non-rapid eye movement (NREM) and a percentage of forgetting at the 1-week delay recall and recognition. This suggests that the interictal spikes interrupt the hippocampal neocortical transfer that should occur during NREM sleep.

Lambert added that in memory consolidation additional studies are needed in rhythm, hippocampal ripples, slow waves and the interplay between the rhythm within the hippocampus as well as the interplay with this rhythm on other brain regions.