Cutaneous sensations at electrode sites during the administration of direct current brain stimulation may inadvertently influence participants' subjective experience and task performance.
The present study evaluated the utility of a methodological variation that substitutes sham administration with very low intensity (0.5 mA) current delivery.
We used a 4 × 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.
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.
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.
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Published online: September 26, 2014
Accepted: September 19, 2014
Received in revised form: September 18, 2014
Received: August 10, 2014
Published by Elsevier Inc.