The effects of high-definition transcranial direct current stimulation on pain modulation and stress-induced hyperalgesia.

Background: The dorsolateral prefrontal cortex (DLPFC) has been implicated in the modulation of pain-related signals. Given this involvement, manipulation of the DLPFC through transcranial direct current stimulation (tDCS) may influence internal pain modulation and decrease pain sensitivity. Acute stress is also thought to affect pain, with increased pain sensitivity observed following the presentation of an acute stressor. Methods: A total of 40 healthy adults (50% male), ranging in age from 19 to 28 years (M = 22.13, SD = 1.92), were randomly allocated to one of two stimulation conditions (active and sham). High-definition tDCS (HD-tDCS) was applied for 10 min at 2 mA, with the anode placed over the left DLPFC. Stress was induced after HD-tDCS administration using a modified version of the Trier Social Stress Test. Pain modulation and sensitivity were assessed through the conditioned pain modulation paradigm and pressure pain threshold measurements, respectively. Results: Compared to sham stimulation, active stimulation produced a significant increase in pain modulation capacity. No significant change in pain sensitivity and stress-induced hyperalgesia was observed following active tDCS. Conclusion: This research shows novel evidence that anodal HD-tDCS over the DLPFC significantly enhances pain modulation. However, HD-tDCS had no effect on pain sensitivity or stress-induced hyperalgesia. The observed effect on pain modulation after a single dose of HD-tDCS over the DLPFC is a novel finding that informs further research into the utility of HD-tDCS in the treatment of chronic pain by presenting the DLPFC as an alternative target site for tDCS-induced analgesia.