Daytime nap helps memory performance

BOSTON, Feb. 1 (UPI) -- A 45-minute daytime nap clearly benefits a person's declarative memory performance, U.S. researchers found.

Study author Matthew A. Tucker of the Center for Sleep and Cognition and 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 to take three different declarative memory tasks at 12:15 p.m., and at 1 p.m.

Sixteen 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.

The study, published in the journal Sleep, showed that, across three very different declarative memory tasks, a nap benefited performance compared to comparable periods of wakefulness, however, 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," Tucker said in a statement. "The importance of this finding is that sleep may not indiscriminately process all information we acquire during wakefulness, only the information we learn well."