A Washington University St. Louis study on memory revealed that “sleeping on it” is, in fact, the most productive plan of action.
Doctoral candidate 
“What we wanted to look at was how we use memory in the future … remembering to take our medication, remembering to mail off a Father’s Day card, and how prospective memory interacts with sleep,” said Scullin in an AOL Health report.
The psychologists believe that prospective memories are stored and strengthened during slow wave sleep, which is colloquially referred to as “deep sleep.” During slow wave sleep, the hippocampus communicates with the cortical regions, which are integral to the storage of memories.
“We think that during slow wave sleep the hippocampus is reactivating these recently learned memories, taking them up and placing them in long-term storage regions in the brain,” said Scullin in a Science Daily report. “The physiology of slow wave sleep seems very conducive to this kind of memory strengthening.”
Scullin and McDaniel also discovered that sleep strengthens weak associations—those loosely related to a memory—in the brain.
Michael Scullin
One of the more provocative findings we have is that sleep didn’t strengthen the link between the explicit cue, which is the person, and the intention,” said McDaniel. “Rather, it strengthened the weak association and the intention.”
An explicit cue would, for example, be the sight of a person to whom you plan to relate a message. A weak association would be the sight of an object you associate with this person, or the room you were in when you made this plan. The relation between sleep and weak associations “hasn’t been shown before,” according to Scullin.
Study participants who were triggered by a weak association improved their prospective memory performance by fifty percent after sleeping, and those who were not provided with context improved by thirty percent after sleeping.
Scullin said that “this performance enhancement” was not displayed by the participants who did not sleep during the study.
Sleep has been linked to retrospective memory—mental retention of events that happened in the past—for years. A 2005 Beth Israel Deaconess Medical Center study suggested sleep as a rehabilitation treatment for stroke patients, and a 2003 University of Chicago study revealed that sleep improves retention of vocabulary words.
Until now, however, little thought had been given to the correlation between sleep and prospective memory.
“The brain is attuned to the future and to solving future goals,” said Scullin.
—Natalie Orenstein/Newsdesk
VIDEO: Secrets of the Sleeping Brain
CITATIONS:
Memory links to 40 winks
Science Daily, June 30, 2010
Want to remember to-do list? Make it before sleeping, study says
AOL Health, July 2, 2010
Study shows how sleep improves memory
Science Daily, June 29, 2010
Sleep boosts memory
Psychology Today, October 1, 2003
that’s why i love sleeping!