Table 1.

Explained ($R_i^2$) and predicted ($Q_i^2$) variance of the first three PLS components (i).

Predictor	r E	${\mathit{R}}_{\mathbf{1}}^{\mathbf{2}}$	${\mathit{R}}_{\mathbf{2}}^{\mathbf{2}}$	${\mathit{R}}_{\mathbf{3}}^{\mathbf{2}}$	${\mathit{Q}}_{\mathbf{1}}^{\mathbf{2}}$	${\mathit{Q}}_{\mathbf{2}}^{\mathbf{2}}$	${\mathit{Q}}_{\mathbf{3}}^{\mathbf{2}}$
Real tDCS
Eabs	1%	0.39	0.44	0.12	0.17*	−0.53	−4.24
Eabs	2%	0.39	0.48	0.10	0.12*	−0.79	−7.36
Eabs	3%	0.39	0.50	0.08	0.09	−0.85	−9.38
Eabs	10%	0.43	0.51	0.05	0.10*	−0.64	−15.93
En	1%	0.54	0.32	0.11	0.12*	−0.99	−5.19
En	2%	0.62	0.32	0.05	0.12*	−1.40	−12.19
En	3%	0.67	0.28	0.04	0.09	−1.94	−19.39
En	10%	0.87	0.12	0.01	−0.00	−7.04	−88.15
Sham
Eabs	1%	0.23	0.50	0.17	−0.23	−1.33	−5.61
Eabs	2%	0.30	0.51	0.15	−0.28	−1.46	−8.27
Eabs	3%	0.33	0.51	0.14	−0.32	−1.58	−9.85
Eabs	10%	0.39	0.54	0.06	−0.38	−1.67	−20.76
En	1%	0.58	0.25	0.12	−0.32	−2.60	−8.17
En	2%	0.66	0.23	0.09	−0.25	−3.21	−12.70
En	3%	0.71	0.22	0.06	−0.23	−3.88	−18.91
En	10%	0.89	0.10	0.01	−0.13	−9.03	−122.36

The predictor variables are the EF absolute value or the normal component and the dependent variables are the mean normalized MEP of either real tDCS or sham stimulation. Ratio r_E indicates the percentage of the highest EF values used for the PLS regression. *Q² > 0.0975.