TABLE 7.

Pearson product-moment correlations between cognitive performance-relevant parameters and vagally mediated heart rate variable parameters during the single stimulation phase (tVNS) and the task phase (task) for active and sham conditions. Coefficients for the cognitive flexibility tasks.

			Active Stimulation					Sham Stimulation
			RT		Percentage error			RT		Percentage error
			Non-switch trials	Switch trials	Non-switch trials	Switch trials	Switch costs	Non-switch trials	Switch trials	Non-switch trials	Switch trials	Switch costs
NLT
RMSSD	tVNS	Pearson’s r	–0.28	–0.24	0.40*	0.14	0.13	0.12	0.15	0.19	–0.06	–0.02
		p-value	0.132	0.179	0.025	0.434	0.434	0.513	0.430	0.308	0.727	0.934
	Task	Pearson’s r	–0.06	–0.03	0.33	0.31	0.13	0.10	0.29	0.22	–0.02	0.28
		p-value	0.732	0.860	0.070	0.081	0.475	0.595	0.113	0.238	0.909	0.115
HF	tVNS	Pearson’s r	−0.44*	−0.50**	0.37*	0.31	0.14	0.09	–0.10	0.11	–0.23	–0.28
		p-value	0.015	0.005	0.046	0.099	0.463	0.677	0.626	0.599	0.279	0.170
	Task	Pearson’s r	−0.39*	–0.24	0.28	0.22	0.42*	–0.10	–0.02	0.48*	0.07	0.15
		p-value	0.034	0.204	0.129	0.242	0.020	0.621	0.914	0.015	0.748	0.482
DCCS
RMSSD	tVNS	Pearson’s r	–0.27	–0.17	0.24	0.29	0.40*	0.09	0.04	–0.03	–0.01	–0.10
		p-value	0.134	0.351	0.180	0.103	0.024	0.623	0.837	0.869	0.973	0.603
	Task	Pearson’s r	–0.25	–0.14	0.16	0.23	0.37*	0.06	0.01	0.03	0.02	–0.08
		p-value	0.177	0.440	0.385	0.212	0.035	0.741	0.953	0.858	0.920	0.660
HF	tVNS	Pearson’s r	−0.40*	−0.42*	0.29	0.31	–0.08	0.05	0.04	–0.19	–0.14	0.03
		p-value	0.026	0.018	0.110	0.089	0.684	0.796	0.835	0.356	0.483	0.900
	Task	Pearson’s r	0.07	–0.01	–0.27	–0.19	−0.42*	–0.05	–0.03	0.02	–0.06	0.10
		p-value	0.715	0.970	0.150	0.314	0.019	0.819	0.905	0.931	0.761	0.619

*p < 0.05, **p < 0.01. Non-adjusted p values. RT = reaction times; RMSSD = root mean square of successive differences; HF = high frequency; NLT = Number Letter task; DCCS = Dimensional Change Card Sorting task; tVNS = transcutaneous vagus nerve stimulation (single stimulation phase).