Table 1.

Means (SD) and correlations for amplitudes and latencies of evoked P50 responses during REM (active sleep in infancy) and non-REM (NREM) sleep in infants and 4 year olds.

	Sleep stage	Infany	4 Year-olds	r a	p	ICCb	p	Statistical analyses c
Amplitude S1 (μV)	REM	2.32 (1.17)	2.45 (0.79)	.09	.77	.15	.30	Significant or trending effects:  Sleep stage by stimulus type: F(1,12) = 17.1, p = .001  Stimulus number: F(1,12) = 4.1, p = .004  Age by sleep stage: F (1,12) = 4.1, p = .064  Sleep stage: F (1,12) = 3.9, p = .072
	NREM	2.10 (0.66)	2.48 (0.75)	.23	.46	.06	.41
Amplitude S2 (μV)	REM	1.41 (0.82)	1.20 (0.85)	.33	.25	.42	.06
	NREM	1.83 (0.97)	2.46 (1.19)	−.29	.35	.17	.27
P50 sensory gating ratio	REM	.58 (0.25)	.49 (0.28)	.73	.003	.74	.001	Significant or trending effects:  Sleep stage: F(1,12) = 15.8, p = .002
	NREM	.91 (0.54)	.95 (0.48)	−.05	.88	.17	.27
Latency S1 (ms)	REM	64.5 (15.5)	63.3 (8.5)	−.04	.90	.06	.42	Significant or trending effects:  Sleep stage: F(1,12) = 17.1, p = .023  Age by sleep stage: F = 4.6, p = .053
	NREM	75.2 (18.0)	63.7 (4.7)	.12	.69	.10	.36
Latency S2 (ms)	REM	65.5 (15.2)	65.1 (8.6)	.12	.68	.08	.38
	NREM	75.5 (19.8)	63.5 (5.9)	.30	.32	.22	.21

Amplitudes are significantly reduced in response to the second sound as compared to the first, in both infants and 4 years, during REM but not NREM sleep. Latency of the P50 evoked response is mildly elevated during NREM sleep as compared to REM sleep in infants, but not in 4-year-olds. There is robust P50 sensory gating during REM but not NREM sleep in both infants and 4-year-old children.

S1 refers to the evoked response to the first sound; S2 refers to the evoked response to the second sound.

^aPearson correlation.

^bIntra-class correlation.

^cRepeated measures ANOVA: age × sleep stage × stimulus type (amplitude and latency analyses); age × sleep stage (P50 sensory gating analysis).