TABLE 6.

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.

			Active Stimulation				Sham Stimulation
			RT		Percentage error		RT		Percentage error
			Congruent trials	Incongruent trials	Congruent trials	Incongruent trials	Congruent trials	Incongruent trials	Congruent trials	Incongruent trials
Flanker task
RMSSD	tVNS	Pearson’s r	0.02	–0.05	–0.21	–0.22	–0.29	–0.23	0.26	0.197
		p-value	0.935	0.768	0.243	0.233	0.114	0.207	0.144	0.280
	Task	Pearson’s r	–0.06	–0.08	–0.25	–0.28	–0.24	–0.24	0.16	0.27
		p-value	0.760	0.666	0.171	0.115	0.193	0.189	0.369	0.140
HF	tVNS	Pearson’s r	–0.20	–0.19	0.16	0.23	–0.24	0.01	0.06	0.03
		p-value	0.288	0.334	0.395	0.237	0.262	0.991	0.785	0.906
	Task	Pearson’s r	–0.25	–0.30	–0.09	–0.17	–0.34	–0.18	–0.01	0.07
		p-value	0.189	0.119	0.647	0.378	0.109	0.394	0.987	0.760
Spatial Stroop task
RMSSD	tVNS	Pearson’s r	0.06	–0.04	–0.22	–0.15	−0.42*	−0.39*	–0.12	–0.01
		p-value	0.755	0.845	0.227	0.403	0.018	0.027	0.532	0.987
	Task	Pearson’s r	–0.02	–0.13	–0.18	–0.34	–0.34	–0.31	0.19	0.12
		p-value	0.907	0.485	0.318	0.054	0.059	0.088	0.311	0.514
HF	tVNS	Pearson’s r	–0.25	–0.27	–0.11	0.28	−0.43*	–0.32	0.17	0.45*
		p-value	0.175	0.151	0.579	0.131	0.038	0.142	0.437	0.032
	Task	Pearson’s r	–0.20	–0.07	–0.17	0.12	–0.27	–0.24	0.11	0.10
		p-value	0.302	0.715	0.376	0.539	0.219	0.264	0.623	0.642

Coefficients for the inhibitory control tasks. *p < 0.05. Non-adjusted p-values. RT, reaction times; RMSSD, root mean square of successive differences; HF, high frequency; tVNS, transcutaneous vagus nerve stimulation (single stimulation phase).