title: Transcranial Direct Current Stimulation (tDCS) Targeting Left Dorsolateral Prefrontal Cortex Modulates Task-Induced Acute Pain in Healthy Volunteers.
abstract: OBJECTIVE
  Current chronic pain treatments target nociception rather than affective "suffering" and its associated functional and psychiatric comorbidities. The left dorsolateral prefrontal cortex (DLPFC) has been implicated in affective, cognitive, and attentional aspects of pain and is a primary target of neuromodulation for affective disorders. Transcranial direct current stimulation (tDCS) can non-invasively modulate cortical activity. The present study tests whether anodal tDCS targeting the left DLPFC will increase tolerability of acute painful stimuli vs cathodal tDCS.
  
  
  METHODS
  Forty tDCS-naive healthy volunteers received anodal and cathodal stimulation targeting the left DLPFC in two randomized and counterbalanced sessions. During stimulation, each participant performed cold pressor (CP) and breath holding (BH) tasks. We measured pain intensity with the Defense and Veterans Pain Rating Scale (DVPRS) before and after each task.
  
  
  RESULTS
  Mixed ANOVA revealed no main effect of stimulation polarity for mean CP threshold, tolerance, or endurance, or mean BH time (allP > 0.27). However, DVPRS rise associated with CP was significantly smaller with anodal vs cathodal tDCS (P = 0.024). We further observed a significant tDCS polarity × stimulation order interaction (P = 0.042) on CP threshold, suggesting task sensitization.
  
  
  CONCLUSIONS
  Although our results do not suggest that polarity of tDCS targeting the left DLPFC differentially modulates the tolerability of CP- and BH-related pain distress in healthy volunteers, there was a significant effect on DVPRS pain ratings. This contrasts with our previous findings that tDCS targeting the left dorsal anterior cingulate cortex showed a trend toward higher mean CP tolerance with cathodal vs anodal stimulation. The present results may suggest tDCS-related effects on nociception or DLPFC-mediated attention, or preferential modulation of the affective valence of pain as captured by the DVPRS. Sham-controlled clinical studies are needed.
authors.affiliation: *Department of Psychiatry and Human Behavior, Warren Alpert Medical School, Brown University, Providence, Rhode Island Center of Excellence for Neurorestoration and Neurotechnology, Providence Veterans Affairs Medical Center, Providence, Rhode Island, USA mariano@post.harvard.edu.
authors.forename: Timothy Y
authors.initials: TY
authors.lastname: Mariano
authors.affiliation: *Department of Psychiatry and Human Behavior, Warren Alpert Medical School, Brown University, Providence, Rhode Island Center of Excellence for Neurorestoration and Neurotechnology, Providence Veterans Affairs Medical Center, Providence, Rhode Island, USA.
authors.forename: Mascha
authors.initials: M
authors.lastname: Van't Wout
authors.affiliation: *Department of Psychiatry and Human Behavior, Warren Alpert Medical School, Brown University, Providence, Rhode Island.
authors.forename: Sarah L
authors.initials: SL
authors.lastname: Garnaat
authors.affiliation: *Department of Psychiatry and Human Behavior, Warren Alpert Medical School, Brown University, Providence, Rhode Island Center of Excellence for Neurorestoration and Neurotechnology, Providence Veterans Affairs Medical Center, Providence, Rhode Island, USA.
authors.forename: Steven A
authors.initials: SA
authors.lastname: Rasmussen
authors.affiliation: *Department of Psychiatry and Human Behavior, Warren Alpert Medical School, Brown University, Providence, Rhode Island Center of Excellence for Neurorestoration and Neurotechnology, Providence Veterans Affairs Medical Center, Providence, Rhode Island, USA.
authors.forename: Benjamin D
authors.initials: BD
authors.lastname: Greenberg
mesh_terms: D059787:Acute Pain / Q000503:physiopathology*; D000293:Adolescent; D000328:Adult; D000368:Aged; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D008297:Male; D008875:Middle Aged; D017288:Pain Threshold; D017397:Prefrontal Cortex / Q000503:physiopathology*; D065908:Transcranial Direct Current Stimulation / Q000379:methods*; D055815:Young Adult
keywords: DLPFC; Dorsolateral Prefrontal Cortex; Neuromodulation; Pain; Transcranial Direct Current Stimulation; tDCS
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