Delayed onset of a daytime nap facilitates retention of declarative memory.
BACKGROUND
Learning followed by a period of sleep, even as little as a nap, promotes memory consolidation. It is now generally recognized that sleep facilitates the stabilization of information acquired prior to sleep. However, the temporal nature of the effect of sleep on retention of declarative memory is yet to be understood. We examined the impact of a delayed nap onset on the recognition of neutral pictorial stimuli with an added spatial component.


RESULTS
Participants completed an initial study session involving 150 neutral pictures of people, places, and objects. Immediately following the picture presentation, participants were asked to make recognition judgments on a subset of "old", previously seen, pictures versus intermixed "new" pictures. Participants were then divided into one of four groups who either took a 90-minute nap immediately, 2 hours, or 4 hours after learning, or remained awake for the duration of the experiment. 6 hours after initial learning, participants were again tested on the remaining "old" pictures, with "new" pictures intermixed.


CONCLUSIONS
Interestingly, we found a stabilizing benefit of sleep on the memory trace reflected as a significant negative correlation between the average time elapsed before napping and decline in performance from test to retest (p = .001). We found a significant interaction between the groups and their performance from test to retest (p = .010), with the 4-hour delay group performing significantly better than both those who slept immediately and those who remained awake (p = .044, p = .010, respectively). Analysis of sleep data revealed a significant positive correlation between amount of slow wave sleep (SWS) achieved and length of the delay before sleep onset (p = .048). The findings add to the understanding of memory processing in humans, suggesting that factors such as waking processing and homeostatic increases in need for sleep over time modulate the importance of sleep to consolidation of neutral declarative memories.
Alger
Sara E
SE
Department of Psychology, The City College of the City University of New York, New York, New York, United States of America. sealger78@gmail.com
Lau
Hiuyan
H
Fishbein
William
W
D000293:Adolescent; D000328:Adult; D000704:Analysis of Variance; D005260:Female; D006801:Humans; D008297:Male; D010364:Pattern Recognition, Visual / Q000502:physiology; D012153:Retention, Psychology / Q000502:physiology*; D012890:Sleep / Q000502:physiology*; D012895:Sleep, REM / Q000502:physiology; D013997:Time Factors; D014851:Wakefulness / Q000502:physiology; D055815:Young Adult
Brain Res Bull. 2003 Dec 15;62(2):143-50
14638388
Learn Mem. 2004 Nov-Dec;11(6):679-85
15576885
Brain Res. 1982 Aug 19;246(1):178-80
7127087
Neuroscientist. 2006 Oct;12(5):410-24
16957003
Science. 1971 Apr 2;172(3978):80-2
4322958
Proc Natl Acad Sci U S A. 2003 Feb 18;100(4):2065-9
12576550
J Cogn Neurosci. 1997 Jul;9(4):534-47
23968216
Psychol Sci. 2008 Aug;19(8):781-8
18816285
Sleep Med Rev. 2001 Dec;5(6):491-506
12531156
Nat Neurosci. 2005 Nov;8(11):1560-7
16222227
Nat Neurosci. 2004 Mar;7(3):286-94
14983183
Proc Natl Acad Sci U S A. 2005 Dec 13;102(50):18237-41
16330773
Nature. 2003 Oct 9;425(6958):614-6
14534586
Neurobiol Learn Mem. 2006 Sep;86(2):241-7
16647282
J Neurosci. 2009 Apr 22;29(16):5143-52
19386910
Sleep Med Rev. 2006 Feb;10(1):49-62
16376591
Exp Brain Res. 2010 Jun;203(2):471-7
20401652
Behav Biol. 1977 Apr;19(4):425-64
16586
Behav Brain Res. 1996 Jun;78(1):49-56
8793037
Curr Opin Neurobiol. 2006 Dec;16(6):716-22
17085038
Science. 1997 May 23;276(5316):1265-8
9157887
Proc Natl Acad Sci U S A. 2007 Nov 20;104(47):18778-83
18000060
Brain Res. 1983 Oct;287(2):139-71
6357356
Psychol Sci. 2006 Oct;17(10):891-8
17100790
Cereb Cortex. 2009 May;19(5):1158-66
18832332
J Exp Psychol. 1967 Sep;75(1):64-72
6065839
Proc Natl Acad Sci U S A. 2005 Oct 25;102(43):15676-81
16221767
Neurobiol Learn Mem. 2008 Jan;89(1):76-80
17911036
Can J Psychol. 1991 Jun;45(2):115-24
1873751
Neuroscience. 1989;31(3):551-70
2687720
Science. 1994 Jul 29;265(5172):676-9
8036517
Proc Natl Acad Sci U S A. 2004 Sep 21;101(38):13963-8
15356341
Science. 2007 Mar 9;315(5817):1426-9
17347444
Neuron. 2004 Sep 30;44(1):121-33
15450165
Cereb Cortex. 2008 Nov;18(11):2494-504
18375529
Curr Biol. 2006 Jul 11;16(13):1290-4
16824917
Psychol Sci. 2010 Jan;21(1):80-5
20424027
Nat Neurosci. 2003 Jul;6(7):697-8
12819785
Proc Natl Acad Sci U S A. 2006 Jan 17;103(3):756-61
16407110
Nature. 2005 Oct 27;437(7063):1272-8
16251952
Brain Res. 1995 Sep 18;692(1-2):79-85
8548323
Neuron. 2001 Jan;29(1):145-56
11182087
Nat Neurosci. 2007 Jan;10(1):100-7
17173043
Neuron. 2004 Oct 28;44(3):535-45
15504332
Sleep Med. 2006 Sep;7(6):508-12
16931152
Nat Neurosci. 2007 Oct;10(10):1241-2
17828259
Trends Cogn Sci. 1999 Sep;3(9):351-359
10461198
Learn Mem. 2004 Nov-Dec;11(6):697-704
15576887
J Neurosci. 2002 Aug 1;22(15):6830-4
12151563
Nature. 2004 Jul 1;430(6995):78-81
15184907