Abstract
Background
Prior investigations employing transcranial direct current stimulation (tDCS) have
shown that stimulation can elicit subsequent improvement on tests of various cognitive
abilities, including working memory. While stimulation parameters such as intensity
and duration are known to determine the effects of tDCS, the degree to which stimulation
effects are influenced by the nature of cognitive activities during stimulation remains
unclear.
Objective/hypothesis
To determine whether manipulating the working memory load of a task performed during
stimulation would modulate tDCS-induced enhancement of performance on a different,
related measure after stimulation.
Methods
In two separate but closely related sham-controlled experiments, two groups of healthy
subjects underwent anodal tDCS (2 mA) of the left dorsolateral prefrontal cortex (DLPFC)
for 20 min. In Experiment 1, subjects (n = 11) trained on a letter 3Back task during stimulation. In Experiment 2 subjects
(n = 11) trained on a letter 1Back task, which resembled the 3Back task but featured
a lower working memory load. In both experiments, before and after stimulation, subjects
completed an adjusting Paced Auditory Serial Addition Task (A-PASAT). Both the experimenter
and subjects were blind to stimulation conditions in both experiments.
Results
Subjects were both faster and more accurate on the A-PASAT task after receiving real
tDCS paired with 3Back training (Experiment1) compared to sham+3Back, real+1Back,
and sham+1Back conditions.
Conclusions
The cognitive demands of a task performed during tDCS can influence the effects of
tDCS on post-stimulation performance. This finding has direct relevance to the use
of tDCS as an investigative tool in cognitive neuroscience and as a therapy.
Keywords
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Article Info
Publication History
Published online: November 05, 2014
Accepted:
October 29,
2014
Received:
August 26,
2014
Identification
Copyright
© 2015 Elsevier Inc. Published by Elsevier Inc. All rights reserved.
