Differential effects of sleep on explicit and implicit memory for potential trauma reminders: findings from an analogue study

Figures & data

Figure 1. Trial sequence of ‘traumatic’ picture stories.

Green frames indicate neutral pictures, red frames indicate ‘traumatic’ pictures and blue frames indicate primes.

Figure 2. Trial sequence of the blurred picture identification task (a) and the recognition test (b).

Table 1. Sample characteristics.

	Sleep group n = 20	PSD group n = 21	Group comparison
Age	22.71 (2.83)	22.15 (2.16)	t(39) = 0.72, p = .479, d = 0.23
Gender	14 ♀/7♂	13 ♀/7♂	χ^2(1) = 0.01 p = .910, η^2 = = 0.03
Average sleep duration (h)	7.83 (.75)	7.59 (.66)	t(39) = 1.12, p = .271, d = 0.35
Sleep Quality (PSQI)	3.24 (1.22)	3.30 (1.26)	t(39) = 0.16, p = .874, d = 0.05
Daytime Sleepiness (ESS)	7.24 (4.35)	7.30 (2.64)	t(39) = 0.06, p = .957, d = 0.02
Circadian Preference (rMEQ)	15.67 (2.37)	16.00 (2.83)	t(39) = 0.41, p = .684, d = 0.13
Depressive symptoms (PHQ-9)	4.38 (3.32)	3.75 (2.27)	t(39) = 0.71, p = .484, d = 0.22
Picture story rating
Valence	26.99 (13.76)	21.86 (11.02)	t(39) = 1.31, p = .197, d = 0.41
Arousal	63.18 (14.75)	58.78 (22.40)	t(39) = 0.75, p = .460, d = 0.23

PSQI = Pittsburgh Sleep Quality Index, ESS = Epworth Sleepiness Scale, rMEQ = reduced Morningness-Eveningness Questionnaire, PHQ-9 = Patient Health Questionnaire; means and standard deviations are given in parentheses, all p-values reflect two-sided tests.

Table 2. Sleep stage data.

		Sleep group n = 20	PSD group n = 21	Group comparison
1st night half	TST	215.22 (8.73)	214.95 (12.10)	t(39) = 0.08, p = .934, d = 0.03
	N1	29.75 (18.23)	24.90 (13.58)	F(1,39) = 0.92, p = .342, η^2p = 0.02
	N2	96.23 (22.75)	107.67 (16.96)	F(1,39) = 3.27, p = .078, η^2p = 0.08
	N3	65.67 (15.23)	61.68 (20.44)	F(1,39) = 0.50, p = .482, η^2p = 0.01
	REM	23.52 (12.48)	20.70 (11.33)	F(1,39) = 0.57, p = .453, η^2p = 0.02
	WAKE	13.11 (8.07)	14.05 (11.96)	F(1,39) = 0.09, p = .769, η^2p = 0.01
2nd night half	TST	217.86 (7.24)	-	-
	N1	37.87 (16.50)	-	-
	N2	104.22 (17.45)	-	-
	N3	11.21 (10.23)	-	-
	REM	64.56 (11.41)	-	-
	WAKE	9.46 (7.60)	-	-
Total	TST	433.08 (12.47)	214.95 (12.10)	t(39) = 56.82, p < .001, d = 17.75
	N1	67.62 (33.23)	24.90 (13.58)	F(1,39) = 28.49, p < .001, η^2p = 0.42
	N2	200.51 (35.69)	107.67 (16.96)	F(1,39) = 111.31, p < .001, η^2p = 0.74
	N3	76.87 (22.79)	61.68 (20.44)	F(1,39) = 5.03, p = .031, η^2p = 0.11
	REM	88.08 (17.92)	20.70 (11.33)	F(1,39) = 204.75, p < .001, η^2p = 0.84
	WAKE	22.57 (11.93)	14.05 (11.96)	F(1,39) = 5.21, p = .028, η^2p = 0.12
% TST	N1	15.63 (7.63)	11.55 (6.29)	F(1,39) = 3.45, p = .071, η^2p = 0.08
	N2	46.32 (8.27)	49.99 (6.84)	F(1,39) = 2.39, p = .130, η^2p = 0.06
	N3	17.72 (5.12)	28.81 (9.79)	F(1,39) = 20.93, p < .001, η^2p = 0.35
	REM	20.33 (4.01)	9.65 (5.40)	F(1,39) = 52.11, p < .001, η^2p = 0.57

TST = Total sleep time, WAKE = Wake after sleep onset, N1 = NREM Stage 1, N2 = NREM Stage 2, N3 = NREM Stage 3 (corresponding to SWS), REM = REM sleep; means and standard deviations are given in parentheses, all p-values reflect two-sided tests.

Table 3. Memory performance and intrusion frequency.

	Sleep group	PSD group
Priming score	−0.09 (0.18)	−0.10 (0.17)
Primed	0.47 (0.14)	0.46 (0.15)
Unprimed	0.57 (0.17)	0.56 (0.13)
Recollection	0.89 (0.47)	0.55 (0.37)
Familiarity	0.55 (0.41)	0.74 (0.52)
Hits	0.38 (0.14)	0.47 (0.14)
FA	0.11 (0.09)	0.16 (0.10)
Intrusion frequency	1.29 (1.52)	2.75 (3.63)

Untransformed intrusion frequency means are presented for greater comprehensibility; means and standard deviations given in parentheses.

Figure 3. Group means of (a) recognition memory (* = p < 0.05, one-sided), (b) intrusion frequency (* = p < 0.05, one-sided), and (c) priming scores (* = p < 0.05, two-sided).

Figure C depicts untransformed means for greater comprehensibility; whiskers indicate the standard error of the mean.