Understanding the Neural and Behavioral Correlates of Mind Wandering Through Transcranial Direct Current Stimulation

Abstract

The mind’s tendency to wander is an integral part of the human experience. Recent studies suggest that high-level cognitive functions such as mind wan- dering (MW) can be modulated by non-invasive brain stimulation (NIBS) techniques such as transcranial direct current stimulation (tDCS). However, the effectiveness of tDCS in the cognitive domain remains an issue of debate. This thesis aimed to understand if tDCS is effective in modulating MW, either on the behavioral or neural levels, by employing rigorous, transparent, open science practices that include open availability of data and materials, such as analysis scripts. In a high-powered (N = 192) preregistered replication attempt in Paper I, we fail to replicate the finding that anodal tDCS applied to the left dorsolateral prefrontal cortex (DLPFC) increases MW propensity. In contrast, a small effect was found in the opposite direction, though this was not robust. Further, tDCS did not impact any of our task performance measures. In Paper II, we showed that bipolar montages targeting the left DLPFC induce widespread effects extending far beyond the target site by simulation of tDCS-induced electric field (E-field) in the brain. However, E-field elicited by multi-electrode 4 × 1 HD-tDCS montages tended to be more focal, generally confined within the ring created by the four return electrodes. In Paper III, 4 × 1 HD-tDCS targeting the left DLPFC combined with our novel task showed reduced MW propensity for the group receiving active stimulation when compared with the sham group, without impacting task performance. These results highlight the value of preregistered replications in tDCS research in general, and the effectiveness of 4 × 1 HD-tDCS in modulating MW in particular. A NIBS method that can reliably regulate MW will have implications for conditions that are associated with the unfavorable behavioral effects of MW.