Stimulating task unrelated thoughts: tDCS of prefrontal and parietal cortices leads to polarity specific increases in mind wandering

Mind wandering has been associated with both adaptive outcomes and performance impairment, depending on the context. Recently, non-invasive brain stimulation has been applied in several studies with the aim to investigate the neural region(s) casually involved in mind wandering. However, to date there has been little definitive work assessing whether or not the stimulation of different brain regions leads to distinct mind wandering outcomes. The present preregistered study considered the role of the prefrontal cortex and inferior parietal lobule in mind wandering using two stimulation intensities (1mA and 2mA) and two stimulation polarity montages. One-hundred and fifty subjects were randomly allocated to one of the four active stimulation groups or a sham group. Participants' mind wandering propensity was measured via a task unrelated thought probe dispersed throughout an attention-based task completed directly after stimulation. Anodal stimulation to the prefrontal cortex, and cathodal stimulation to the inferior parietal lobule, increased mind wandering propensity and this effect was relatively unaffected by stimulation dosage. These findings support a causal role for these two regions in mind wandering, one that is polarity specific.