Table 2.

Number, density (#/min NREM), duration (s), amplitude (uV²), and peak frequency (Hz) of non‐REM sleep spindles at Fz (midline frontal), Cz (midline central), and Pz (midline posterior) during the 90‐min daytime nap retention interval in young and older participants

	Young		Older		t	P
	M	SE	M	SE
Number
Fz	241.54	20.59	176.60	31.10	1.68	0.212
Cz	251.54	21.31	186.13	31.73	1.65	0.112
Pz	259.54	22.84	181.07	32.33	1.91	0.204
Density
Fz	4.33	0.25	4.82	0.11	−1.83	0.780
Cz	4.51	0.25	5.21	0.15	−2.39	0.072
Pz	4.64	0.26	4.88	0.17	−0.76	0.908
Duration
Fz	0.47	0.02	0.36	0.02	3.70	0.003a
Cz	0.48	0.03	0.34	0.02	3.55	0.002a
Pz	0.49	0.04	0.38	0.03	2.29	0.030a
Amplitude
Fz	59.45	7.68	40.00	4.61	2.16	0.123
Cz	90.18	12.32	67.24	8.12	1.50	0.298
Pz	73.28	10.99	71.80	11.55	0.09	0.930
Frequency
Fz	12.99	0.08	12.65	0.06	3.33	0.009a
Cz	13.36	0.07	13.29	0.10	0.55	0.585
Pz	13.42	0.09	13.51	0.10	−0.64	1.000

^aIndicates P < 0.05, two‐tailed.

df = 26, corrected for homogeneity of variance, where appropriate and Holm‐Bonferroni corrected for multiple comparisons for number of sites.