Polarity- and valence-dependent effects of prefrontal transcranial direct current stimulation on heart rate variability and salivary cortisol - Brunoni, André Russowsky; Vanderhasselt, Marie-Anne; Boggio, Paulo S; Fregni, Felipe; Dantas, Eduardo Miranda; Mill, José G; Lotufo, Paulo Andrade; Benseñor, Isabela Judith Martins (Psychoneuroendocrinology, 2013)