Transcranial Direct Current Stimulation Modulates Performance in Challenging Situations

Eric Blumberg

Advisor: Matthew S. Peterson, PhD, Department of Psychology

Committee Members: Pamela M. Greenwood, Tyler H. Shaw

David J. King Hall, #2073A Arch Lab Conference Room
April 12, 2016, 12:00 PM to 09:00 AM


Transcranial direct current stimulation (tDCS) is a promising tool to improve cognitive abilities, however, a number of questions remain. When is it most effective and how does it affect the brain leading to such diverse cognitive benefits? In the following experiments we tested the extent to which tDCS modulated performance during varying levels of task load in three different visuospatial tasks. Therefore, stimulation was targeted over the right parietal cortex, an area associated with spatial processing.

            Experiment 1 tested whether stimulation could modulate the number of spatial based errors participants committed in a procedural task following an interruption (math problems). Participants were assigned to one of three stimulation conditions: anodal, cathodal or sham. Anodal stimulation significantly reduced the number of spatial errors while cathodal stimulation significantly increased the number of spatial errors. The results demonstrated that the effects of stimulation are bi-directional and that anodal stimulation can be used to reduce the negative effects associated with interrupted task performance.

            Experiment 2 tested whether right parietal anodal stimulation could increase multiple object tracking (MOT) accuracy. Participants completed a MOT task under low and high tracking load levels prior to and during stimulation. Participants were randomly assigned to one of the three stimulation conditions: right parietal anodal, left prefrontal anodal, left prefrontal sham. Right parietal anodal stimulation significantly increased MOT accuracy under the high tracking load compared to the other conditions. Stimulation was also more effective for participants who had lower baseline MOT accuracies suggesting that baseline ability moderated the stimulation-based effect.

            Experiment 3 tested whether right parietal stimulation could affect performance in a complex supervisory control task where task load was systematically changed between low to high levels. Cerebral blood flow velocity (CBFV), an index of mental resource allocation was simultaneously recorded during gameplay to explore how tDCS impacts the brain. Participants were randomly assigned to either the anodal, cathodal, or sham conditions. We ran a cluster analysis in order to account for individual differences in baseline cognitive abilities. The results revealed that anodal stimulation significantly reduced performance compared to cathodal stimulation, potentially through an inhibitory effect on executive control. However, there were no differences in CBFV between the stimulation conditions.