Modulating decision strategies with tDCS; a role for fronto-striatal structural connectivity

Brisbane Convention & Exhibition Centre 

A ubiquitous phenomenon in cognitive psychology, which reflects strategic decision making, is the speed accuracy trade off (SAT); the faster individuals make a decision, the more likely they are to make an error. Previous imaging work has implicated frontal (including the pre-supplementary motor area) and striatal regions, and connectivity between the two, in the SAT, but the nature of this association remains unclear and, to date, previous studies on this topic have employed small sample sizes. Here, we report a large-scale pre-registered, study combining transcranial direct current stimulation (tDCS), ultra-high field (7T) imaging, and computational modelling investigating white matter connectivity and its association with the influence of brain stimulation of decision-making strategy. Across two stimulation sessions, participants completed a task with an instruction-based manipulation of decision strategy – prioritise speed or accuracy, or balance the two – whilst discriminating motion from a patch of moving dots. Offline cathodal stimulation (or sham) was applied at 0.7mA to the superior medial frontal cortex or the left prefrontal cortex. Utilising an individual differences approach, imaging of white matter tracks provided evidence for a role of structural connectivity between frontal and striatal regions in both the SAT and the efficacy of tDCS to modulate performance. Further, group level effects of tDCS on the SAT were found following stimulation to both regions, replicating previous findings. This work provides causal evidence for the involvement of both the left prefrontal and superior medial frontal cortex in the SAT and highlight a role of fronto-striatal connectivity in decision making strategy more broadly.