Table 1.

Average values of the amplitudes of δ-wave, λ, HF_n, A_RSA, f_R, and range of f_R calculated separately in the intervals of high and low δ-wave activity during 1–3 sleep cycles.

	Sleep cycle
Parameters	1		2		3
	H	L	H	L	H	L
δ-wave, μV	94 ± 25**	35 ± 7	85 ± 27**	32 ± 6	81 ± 23**	31 ± 6
λ	0.64 ± 0.12**	0.45 ± 0.13	0.60 ± 0.12**	0.40 ± 0.12	0.57 ± 0.14**	0.39 ± 0.11
HFn	0.65 ± 0.16**	0.51 ± 0.16	0.61 ± 0.19**	0.49 ± 0.16	0.62 ± 0.21**	0.52 ± 0.17
ARSA, ms	79 ± 56**	68 ± 52	82 ± 63**	75 ± 59	80 ± 64*	74 ± 58
fR, Hz	0.24 ± 0.03	0.24 ± 0.02	0.24 ± 0.02	0.24 ± 0.02	0.24 ± 0.02	0.24 ± 0.02
fR Range, Hz	0.19 ± 0.03*	0.20 ± 0.03	0.18 ± 0.03*	0.20 ± 0.03	0.18 ± 0.03*	0.20 ± 0.03

Values are mean ± SD.

H and L denote high and low δ-wave activity segments, respectively, discriminated by the mean amplitude of δ-wave over the entire night, i.e., H is the region where amplitude of the δ-wave was greater than the mean amplitude of the δ-wave over the entire night.

HF_n, normalized high frequency component of heart rate variability; A_RSA, amplitude of respiratory sinus arrhythmia; f_R, respiratory frequency; f_R Range, range between the lower and upper corner frequencies where PSD for respiration reduced to 20% of its maximum power.

^**P < 0.01 and

^*P < 0.05 vs. L in each sleep cycle.