Bennefits of Napping

Running Head: BENNEFITS OF NAPPING

Benefits of napping on memory consolidation

Heisterborg T. Student

445410

Erasmus University college, EUC

Benefits of napping on memory consolidation

Daytime napping is a habit of Benefits of napping on memory consolidationmany individuals. Napping starts as a routine for babies but many people continue to take naps across there lifespan. A nap can take minutes but also hours. Different duration of naps have different effects.  Multiple studies have demonstrated that naps improve alertness and memory.  A hypothesis is that napping contributes to memory consolidation.  This review paper will provide an overview of different academic studies on the relation between naps and memory consolidation.  The studies focus on two types of long term memory: declarative memory and procedural memory.  The following five academic sources depict the relation between napping and memory consolidation.

A research article by Backhaus and Junghanns (2006) investigated the effect of a daytime nap compared to a waking condition on the consolidation of declarative and procedural memory.  The focus of this research was on young adolescents aged between 18 and 25 years, who were habitual afternoon nappers. The thirty-four selected participant all performed two tasks on declarative memory and did one procedural memory exercise. The tasks for declarative memory were an associated learning task and an exercise where they had to remember faces and names.  The procedural exercise was a mirror tracing exercise.  Shortly after the task the nap group took a nap and the other group stayed awake.  The performance on the three memory tasks was tested again after the nap.  The data showed that only naps of 45 minutes or more lead to improvement of procedural memory compared to the subjects that stayed awake. On the declarative memory task, the subjects improved without a significant difference between both groups. Interestingly, the nappers with SWS (slow wave sleep) were compared to nappers without SWS sleep and there was a significant difference between their improvement. The nappers with SWS sleep did better on the declarative tasks.  To conclude, procedural memory benefited from napping, while this could not be demonstrated for the improvement of declarative memory (Backhaus & Junghanns, 2006).  One limitation to the study is that only habitual nappers were participants in this research. The final data could have been different when non habitual nappers were subjects. Another limitation is that there were only thirty-four individuals participating in this research, which is nog enough for a solid conclusion.                                                                                         Mednick,  Nakayama, Cantero, Atienza, Levin & Pathak (2002)  have researched the effect of napping time on the procedural memory. This study will explain why the Backhaus & Junghanns (2006) study showed that procedural memory only improves after 45 minutes.  Mednick et al (2002) studied the effects of two different naps: a 30 minute nap and 60 minute nap.  The study subjects were separated into two different groups, both groups performed a procedural task in the form of mirror drawing in advance. One group took a nap for 30 minutes after the task and the other group went to sleep for 60 minutes. Both groups did the procedural task again after this. This study has shown that a 30-minute nap prevents the habitual deterioration across the last two sessions, allowing the maintenance of performance. A long 60-minute nap reverses the impairment and improves performance on procedural memory.  Only the naps that include both SWS and REM led to performance enhancement on procedural memory. The research concluded that SWS sleep in necessary to stabilize performance and Rem results in actual performance improvement.                                  The only disagreement in this study field of daytime naps on procedural memory is found by Tucker, Yasutaka, Wamsley, Lau, Chaklader, & Fishbein (2006). Their research was on both procedural and declarative performance after a short nap. Again there were two groups of subjects. The participants performed a procedural memory task and a declarative memory task. Continuously, one group stayed awake and the other took a short nap of a duration of 50 minutes at 13:00 in the afternoon. After this, the procedural memory task was performed again to see if there was improvement in the procedural performance. No difference was found between sleep and wakefulness when executing a procedural task. So the nap did not improve the procedural results. The explanation for this could be that the duration of the nap was shorter than the duration of the nap that was used in the studies, which proved the importance of napping for memory consolidation. Interestingly enough, Tucker et al (2006) found in their research that the subjects taking a nap improved more at the declarative memory task than the subjects who stayed awake. While the results of the Backhaus and Junghmans (2006) study had reversed result on performance of declarative and procedural memory.                                                                                         Mednick et al. (2002) studied the effect of sleep stages on procedural memory and found that SWS and REM Sleep is needed for an improvement in procedural memory. Possible further research would include the influence of sleep stages on declarative memory. This is exactly what Shabus, Hodlmoser, Pecherstorfer & Klosch (2005) researched. They examined the effect of sleep stages on declarative memory. Two groups were taking a 60-minute nap at 14:00 in the afternoon. The subjects were divided in two groups. One group with SWS and one without SWS sleep. REM sleep was not included because of the short duration. Results indicated that only those nappers with SWS in their sleep showed an improvement at the declarative memory task.                                                          To this end, all academic studies examined whether a nap right after a memory task has influence on performance. The last study by Alger, Lau& Fishbein (2010) examined the impact of a delayed nap on memory performance. Forty-three participants all finished a declarative memory task with pictures associated to people. After that the subjects were divided into four groups, who either took a 90-minute nap immediately after the task, a nap two hours after learning, 4 hours after learning, or remained awake for the duration of the experiment. Six hours after the declarative task, the participants took the task again. Interestingly, they found that the 4-hour delay group performed significantly better than both those groups who slept immediately and those who remained awake. Analysis of sleep data revealed a significant positive correlation between amount of SWS achieved and length of the delay before sleep.                                                                                         To conclude SWS sleep is needed for improvement of declarative memory (Shabus et al, 2005 ), while REM sleep increases the performance of procedural memory consolidation (Mednick et al, 2002). There is a positive correlation between REM and SWS sleep and memory consolidation according to these two studies.  A delayed nap with SWS sleep has more effect on the improvement on memory performance then a nap right after the memory task (Alger et al., 2010).  Tucker et al (2006) was the only study that denied the improvement of procedural memory because of napping. We have cause to neglect those findings because the naps used in this study were of shorter duration than the naps used in studies that proved the positive correlation between napping and procedural memory. To conclude, the studies above have showcased that different duration of naps have different effects on the memory consolidation. Future research is definitely necessary.  It would be interesting to focus on the underlying processes which explain the connections between napping and memory consolidation. In the future, with new technology, neuroscientist should look into the brain and research sleep dependent memory consolidation. With this, we can expand our understanding of the role of naps on the memory processes. A lot of work in the neuroscientific field will be necessary to answer these questions.