Gender difference in the effect of daytime sleep on declarative memory for pictures

Objective: To investigate gender difference in the effects of daytime sleep on item and source memories, which are dissociable elements of declarative memory, and the effects of sleep on recollection and familiarity, which are two processes underlying recognition. Methods: Participants saw a series of pictures with either blue or red background, and were then given a pretest for item and source memories. Then males and females respectively were randomly assigned either to a wake or a sleep condition. In the wake condition, participants remained awake until the posttest; in the sleep condition, participants slept for 1 h until awakened and asked to remain awake until the posttest. Results: Daytime sleep contributed to retention of source memory rather than item memory in females, whereas males undergoing daytime sleep had a trend towards increased familiarity. For females, however, neither recollection nor familiarity appeared to be influenced by daytime sleep. Conclusion: The mechanism underlying gender difference may be linked with different memory traces resulting from different encoding strategies, as well as with different electrophysiological changes during daytime sleep.