A brief bout of non-REM sleep (45 minutes) obtained during a daytime nap clearly benefits a person's declarative memory performance, according to a new study.
The study, authored by Matthew A. Tucker, PhD, of the Center for Sleep and Cognition and the department of psychiatry at Harvard Medical School, focused on 33 subjects (11 males, 22 females) with an average age of 23.3 years. The participants arrived at the sleep lab at 11:30 a.m., were trained on each of the declarative memory tasks at 12:15 p.m., and at 1 p.m., 16 subjects took a nap while 17 remained awake in the lab. After the nap period, all subjects remained in the lab until the retest at 4 p.m.
It was discovered that, across three very different declarative memory tasks, a nap benefited performance compared to comparable periods of wakefulness, but only for those subjects that strongly acquired the tasks during the training session.
"These results suggest that there is a threshold acquisition level that has to be obtained for sleep to optimally process the memory," said Dr. Tucker. "The importance of this finding is that sleep may not indiscriminately process all information we acquire during wakefulness, only the information we learn well."
It is recommended that adults get between seven and eight hours of nightly sleep.
The article "Enhancement of Declarative Memory Performance Following a Daytime Nap is Contingent on Strength of Initial Task Acquisition" was published in the February 1 issue of the journal Sleep.
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