Table 2.

Relationships among parameters by the N-back task, WCST, and CPT-IP and sleep stages.

	Simple correlation analysis		Multiple regression analysis		Simple correlation analysis		Multiple regression analysis
	r	p	β	p	r	p	β	p
0-back task	% corrects				Reaction time
Stage REM	0.282	0.145	0.148	0.645	-0.246	0.206	-0.394	0.196
Stage N1	-0.020	0.920	-0.603	0.476	0.405	0.032	-0.862	0.280
Stage N2	-0.231	0.237	-0.780	0.224	-0.516	0.005	-1.103	0.072
Stage N3	0.252	0.195	-0.033	0.922	-0.035	0.862	-0.148	0.638
1-back task	% corrects				Reaction time
Stage REM	0.202	0.302	0.057	0.871	-0.425	0.024	-0.529	0.046
Stage N1	-0.288	0.137	-0.155	0.866	0.589	0.001	-1.003	0.142
Stage N2	0.244	0.212	0.090	0.896	-0.637	<0.001	-1.276	0.017
Stage N3	0.166	0.397	0.039	0.915	-0.214	0.273	-0.313	0.247
2-back task	% corrects				Reaction time
Stage REM	0.505	0.006	0.559	0.025	-0.507	0.006	-0.690	0.015
Stage N1	-0.637	<0.001	0.616	0.327	0.511	0.005	-0.815	0.253
Stage N2	0.670	<0.001	1.010	0.039	-0.523	0.004	-0.990	0.070
Stage N3	0.161	0.412	0.071	0.774	-0.123	0.532	-0.083	0.767
WCST	Category achievement
Stage REM	0.186	0.343	-0.294	0.359
Stage N1	-0.290	0.134	-1.808	0.039
Stage N2	0.220	0.260	-1.109	0.086
Stage N3	-0.020	0.920	-0.706	0.043
CPT-IP	d-prime
Stage REM	-0.163	0.408	-0.021	0.951
Stage N1	0.206	0.292	0.100	0.914
Stage N2	-0.126	0.524	-0.011	0.988
Stage N3	-0.218	0.266	-0.150	0.687

WCST = Wisconsin card sorting test; CPT-IP = Continuous performance test-identical pairs.