Cathodal and anodal left prefrontal tDCS and the perception of control over pain.

Objectives: The prefrontal cortex may be a promising target for the use of transcranial direct current stimulation (tDCS) in the management of pain symptoms. The present study explored the effects of anodal and cathodal tDCS over the left dorsolateral prefrontal cortex on the effects of perceived pain controllability. Materials and Methods: Forty-one participants received continuous anodal or cathodal tDCS and underwent a laboratory pain task designed to manipulate the perception of pain control. Participants were told that they would be completing a reaction-time task (press keyboard button of corresponding arrow shown on computer screen with either green or red background). A thermal pain stimulus was delivered following each trial by a thermode placed on the participant’s left forearm. Although pain stimuli were pseudorandomally ordered and matched for total duration between control (green) and noncontrol (red) trials, participants were told that if they responded correctly and more quickly on green trials than their average reaction times, the thermal pain stimulus duration would be decreased (ie, perceived control). Participants were told they had no control of pain stimulus duration over trials presented with the red background. Results: There was a significant main effect for tDCS condition (anode vs. cathode) on pain unpleasantness ratings (P < 0.04). Specifically, individuals receiving cathodal tDCS reported higher pain unpleasantness ratings (least squares mean = 69.40, SE = 3.72), whereas those receiving anodal tDCS reported lower pain unpleasantness ratings (least squares mean = 58.05, SE = 3.81). Exploratory analysis revealed a simple main effect for tDCS group at the level of perceived controllability (P < 0.02). In addition, participants receiving cathodal tDCS subjectively reported feeling less control of the painful stimuli than those receiving anodal tDCS.