Mitigating Cutaneous Sensation Differences During tDCS: Comparing Sham Versus Low Intensity Control Conditions

Background: Cutaneous sensations at electrode sites during the administration of direct current brain stimulation may inadvertently influence participants' subjective experience and task performance. Objective: The present study evaluated the utility of a methodological variation that substitutes sham administration with very low intensity (0.5 mA) current delivery. Methods: We used a 4 x 1 high-definition ring electrode transcranial direct current (HD-tDCS) system to target the left dorsolateral prefrontal cortex (Brodmann's Area 9). Four stimulation conditions were compared in a repeated-measures design: sham 2.0 mA and 0.5 mA intensity, versus active 2.0 mA and 0.5 mA intensity. During stimulation participants performed a cognitive interference task that activates the cingulo-frontal-parietal network, and periodically provided perceived sensation ratings. Results: We demonstrate that a relatively low intensity control condition attenuates otherwise large differences in perceived sensation between active and sham conditions. Critically, behavioral task differences maintained between the two active conditions. Conclusion: A low intensity control stimulation condition may prove a viable methodological alternative to conventional sham techniques used in repeated-measures designs, though important limitations are discussed. Published by Elsevier Inc.