Box plot illustrating cold pain thresholds variations related to placebo and real tDCS.

<p>Statistically significant changes occurred in the cold pain thresholds of the left face (<i>p</i> = 0.012) throughout the experiment.</p

Correlation between placebo and real tDCS-induced MOR activation.

<p>MOR BP_ND during placebo (x axis) and real (y axis) tDCS for each subject in the clusters of μ-opioid activation induced by placebo (A–C) and real (D–F) tDCS. The same clusters are illustrated in the <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0102350#pone-0102350-g002" target="_blank">figure 2</a>. Positive correlations can be observed in precuneus and PAG (red lines) but not in thalamus and PFC (blue lines). Statistically significant values at p<0.05 were found in the PAG cluster activated during placebo tDCS (r_p = 0.760, p = 0.013, 3B) and in the precuneus cluster activated during active tDCS (r_p = 0.788, p = 0.008, 3D).</p

Box plot representing tDCS (placebo and real) effects in the heat pain thresholds of both sides of the face.

<p>Statistically significant changes occurred in the heat pain thresholds of the left face (<i>p</i> = 0.032).</p