Causal Dissociation of Frontoparietal Control Mechanisms in Automatic Alcohol Approach Tendencies Using Continuous Theta Burst Stimulation

Abstract

Compulsive alcohol intake is often sustained by approach tendencies that automatically orient individuals toward alcohol-related cues, even when they intend to avoid them. Converging evidence implicates the frontoparietal regions in regulating such automatic behavior; however, the specific contributions of the right dorsolateral prefrontal cortex (rDLPFC) and right posterior parietal cortex (rPPC), and the underlying neurocognitive mechanisms, remain unclear. To determine the specific contributions of these regions, we applied continuous theta burst stimulation (cTBS) to the rDLPFC or rPPC in separate groups of non-clinical alcohol users (rDLPFC: n = 29; rPPC: n = 28) using a within-subject, active-sham counterbalanced design. Alcohol approach tendencies were assessed using the Alcohol Approach-Avoidance Task at baseline and following active and sham stimulation. Active rDLPFC cTBS selectively slowed alcohol push responses without affecting pull responses, whereas rPPC cTBS produced a bidirectional, alcohol-specific shift in which push responses slowed and pull responses simultaneously accelerated. Although stimulation at either site shifted automatic tendencies toward greater alcohol approach, the behavioral profiles were dissociable. The findings suggest that rDLPFC contributes to sustaining the regulatory signal that drives avoidance over prepotent alcohol approach responses, whereas rPPC determines whether that signal is successfully expressed in behavior when competing cue-driven influences are present. These findings provide node-specific evidence for functional specialization within the frontoparietal network and identify a potential parietal mechanism linking cue salience to overt alcohol approach behavior.