The Influence of Skin Redness on Blinding in Transcranial Direct Current Stimulation Studies: A Crossover Trial

Focal Hemodynamic Responses in the Stimulated Hemisphere During High-Definition Transcranial Direct Current Stimulation

“…Nevertheless, the active sham session (active current applied for 1.5 min duration) induces hemodynamic increases that are spatially bound to the 4 × 1 HD‐tDCS montage and outlast the period of stimulation. These sham session findings corroborate with a recent study that showed increased skin blood flow changes (erythema) within the boundaries of the scalp attached conventional (25 cm 2 ) rubber/sponge electrodes after both real anodal tDCS (2 mA for 30 min duration) and active sham tDCS (2 mA current applied for 1.5 min duration), but the extent of the erythema with sham was significantly lower than the real anodal tDCS session.…”

“…It has been previously demonstrated that scalp‐applied anodal tDCS electrical currents induce increases in hemodynamics through cerebral neurovascular coupling mechanisms and skin blood flow/erythema effects under the stimulating electrodes through sensory axon reflex mechanisms . In the present study, it can be suggested HD‐tDCS‐evoked increases in local neuronal activity drove vasodilation increasing O 2 Hb in the stimulated left hemisphere ROIs (Figs.…”

Minimal Heating at the Skin Surface During Transcranial Direct Current Stimulation

“…Our result does not address temperature changes inside the body (e.g., at the brain), temperature changes outside of the period evaluated (up to 5 min post tDCS), microscopic changes (e.g., at sweat pores) or changes following abnormal tDCS dose (e.g., 100 mA), and repeated sessions. We speculate the flare response, already a well‐known consequence of tDCS from inspection of skin erythema , along with the associated skin temperature change indicated here, may influence current flow patterns through the skin, and so indirectly tolerability . For future research, this approach can be extended to a realistic head model or a microscopic level skin model.…”

Blinding is compromised for transcranial direct current stimulation at 1 mA for 20 min in young healthy adults

“…Given that tDCS is a potent placebo-inducing procedure both in the clinical (Aslaksen, Vasylenko, & Fagerlund, 2014) and cognitive domains (Turi, Mittner, Paulus, & Antal, 2017;Turi et al, 2018), there seems to be an urgent need to test alternative active sham protocols (Boonstra, Nikolin, Meisener, Martin, & Loo, 2016;Palm et al, 2013) or develop better active sham protocols to effectively maintain blinding. One possibility may be considering to utilize topical anaesthetic cream to reduce cutaneous sensations (Guarienti et al, 2015;Guleyupoglu, Febles, Minhas, Hahn, & Bikson, 2014;McFadden, Borckardt, George, & Beam, 2011) and vasodilation-induced redness underneath the electrodes (Durand, Fromy, Bouyé, Saumet, & Abraham, 2002;Ezquerro et al, 2017;O'Connell et al, 2012) both of which have previously been identified as potential factors which can break blinding (Guarienti et al, 2015;O'Connell et al, 2012;Palm et al, 2013).…”