Transcranial direct current stimulation (tDCS) and the cardiovascular responses to acute pain in humans

• We tested whether transcranial direct current stimulation (tDCS) alters both pain perception and its cardiovascular responses and if it impacts basal hemodynamics.
• Active tDCS did not affect resting hemodynamics or autonomic outflow.
• Only with the least painful stimulus, tDCS modestly reduced perceived pain and the peak cardiovascular and autonomic responses.

ObjectiveTo determine if transcranial direct current stimulation (tDCS) reduces both acute pain perception and the resultant cardiovascular responses.MethodsData were acquired on 15 healthy subjects at rest and in response to three cold pressor tests: 0, 7, and 14 °C. Subsequently, single sessions of sham and active anodal tDCS (2.0 mA for 40 min) were delivered to the left primary motor cortex (M1).ResultsPerceived pain was reduced only after active tDCS with the 14 °C cold pressor test. This was accompanied by tendency for lesser increases in heart rate (∼2 beats/min, p = 0.09) and blood pressure (∼3 mm Hg, p = 0.06). The effect size of tDCS on peak heart rate and blood pressure responses at 14 °C was 0.47 and 0.54, respectively. On the other hand, baseline heart rate, blood pressure, leg blood flow, and leg vascular resistance were unaffected by tDCS. No other responses were affected.ConclusionsOur results demonstrate that M1 anodal tDCS has no effect on basal hemodynamics or cardiovascular autonomic outflow and has only modest effects on the responses to acute pain in healthy humans.SignificanceApplication of tDCS shifts the pain perception threshold in healthy individuals but does not significantly modulate efferent cardiovascular control at rest or in response to pain.