Menstrual cycle effects on sleep-dependent memory consolidation

A rapidly burgeoning literature documents an effect of midday naps on memory consolidation. But still, the questions of the relevance of EEG-activities (e.g. sleep spindles), sleep phases and the influence of hormones of the menstrual cycle are subject of ongoing discussions. 15 healthy women aged 20–30 with a regular menstrual cycle (no medication) passed through 3 conditions: Each of them once in follicular and once luteal phase resulting in 6 different study days. Two conditions consisted of a learning phase and retest with a nap with polysomnography or a movie before retest and one condition included only a short nap without learning. We used a finger tapping task for procedural memory and verbal paired associate's task for declarative memory. In both tasks the subjects performed significantly better in the third week of their menstrual cycle in comparison to the first week. In addition the subject's memory consolidation only benefited in the third week from a nap. Further we found a correlation between estrogen and the performance in the verbal paired associates task as well as a correlation between progesterone and the motor performance. With this study we are the first to show a menstrual cycle effect on sleep dependent memory consolidation during a nap, which most likely is facilitated through the hormones estrogen and progesterone.