Effects of Transcranial Direct Current Stimulation (tDCS) on Pain Distress Tolerance: A Preliminary Study

Abstract

Objective Pain remains a critical medical challenge. Current treatments target nociception without addressing affective symptoms. Medically intractable pain is sometimes treated with cingulotomy or deep brain stimulation to increase tolerance of pain-related distress. Transcranial direct current stimulation (tDCS) may noninvasively modulate cortical areas related to sensation and pain representations. The present study aimed to test the hypothesis that cathodal (“inhibitory”) stimulation targeting left dorsal anterior cingulate cortex (dACC) would increase tolerance to distress from acute painful stimuli versus anodal stimulation. Methods Forty healthy volunteers received both anodal and cathodal stimulation. During stimulation, we measured pain distress tolerance with three tasks: pressure algometer, cold pressor, and breath holding. We measured pain intensity with a visual-analog scale before and after each task. Results Mixed ANOVA revealed that mean cold pressor tolerance tended to be higher with cathodal versus anodal stimulation (p = 0.055) for participants self-completing the task. Pressure algometer (p = 0.81) and breath holding tolerance (p = 0.19) did not significantly differ. The pressure algometer exhibited a statistically significant order effect irrespective of stimulation polarity (all p < 0.008). Pain intensity ratings increased acutely after cold pressor and pressure algometer tasks (both p < 0.01), but not after breath holding (p = 0.099). Cold pressor pain ratings tended to rise less after cathodal versus anodal tDCS (p = 0.072). Conclusions Although our primary results were nonsignificant, there is a preliminary suggestion that cathodal tDCS targeting left dACC may increase pain distress tolerance to cold pressor. Pressure algometer results are consistent with task-related sensitization. Future studies are needed to refine this novel approach for pain neuromodulation.

Transcranial Direct Current Stimulation (tDCS) Targeting Left Dorsolateral Prefrontal Cortex Modulates Task-Induced Acute Pain in Healthy Volunteers

“…This contrasts with our prior pilot study of tDCS targeting left dACC in another cohort of 40 healthy volunteers that showed a nonsignificant trend towards increased mean CP tolerance with cathodal versus anodal stimulation and no significant effects on DVPRS (30). …”

“…It should be noted that this hypothesis differs from that of our prior study (30). In that work, we theorized that cathodal (“inhibitory”) tDCS targeting left dorsal anterior cingulate cortex (dACC) would decrease emotional distress from acute painful stimuli versus anodal stimulation, based partially on cingulotomy literature showing that ablation of dACC could selectively increase pain tolerability without necessarily decreasing pain intensity (31–34).…”

“…The design of the present study was adapted from our previous study (30). The methods are briefly reviewed below, with key differences described in further detail.…”

“…For the present study, we wished to focus on the cold pressor (CP) task (41), as in our prior study it had exhibited trend-level effects suggesting possible modulation by cathodal tDCS targeting left dACC (30). To that end, in each testing block we administered CP first, followed by the breath holding (BH) task (42,43).…”

“…In no instance did the preprogrammed 20 minutes of tDCS elapse before all tasks were completed. CP involved immersing the participant's dominant (right) hand and arm in an ice water bath using our previously described apparatus (30). Briefly, our apparatus consisted of an insulated vessel with a cylindrical mesh screen to separate the ice from the remainder of the water bath and thus prevent direct contact between ice and a participant's skin.…”