Acute Anxiety Selectively Enhances Value-Free Random Exploration Through Frontoparietal Engagement

Motivational decision-making is most adaptive when exploitation of known rewards is effectively balanced against exploration of uncertain alternatives. Trait anxiety influences this balance across individuals, yet less is known about the dynamic effects of acute anxiety on behaviour. This study combined a decision-making task, the multi-armed bandit Maggie’s Farm task, with fMRI and computational modelling to examine how experimentally induced anxiety modulates exploration strategies (random, value-free exploration versus directed, novelty-seeking exploration) and their neural correlates. Forty-seven healthy participants (24 female; 23 male) completed the task under alternating conditions of safety and anxiety induced by unpredictable electric shocks. Exploratory behaviour was promoted through different task decision horizons and modelled using parameters capturing random value-free exploration (ε) and novelty seeking (η). Acute anxiety impaired performance and decision consistency, selectively increasing random, value-free exploration without affecting novelty-driven exploration. Reaction times decreased, indicating faster, less deliberative responding. Neuroimaging revealed that horizon manipulations recruited circumscribed frontoparietal regions. Value and policy signals were dissociable, with ventromedial prefrontal cortex encoding expected value and superior parietal lobule mediating exploratory control. Critically, acute anxiety increased activation in right superior parietal lobule and frontopolar cortex specifically during random, value-free exploration, independently of value processing. Together with the behavioural findings, this pattern identifies a neural signature of anxiety-related decision noise. In conclusion, acute anxiety increases random, value-independent exploration, promoting less goal-directed, more stochastic behaviour. These findings link anxiety-induced decision noise to frontoparietal activation and identify random exploration as a computational marker of dysregulated anxiety-related decision-making. Significance statement Understanding how anxiety alters decision-making is crucial because anxious states are common and often impair flexible behaviour. Exploration is a key component of adaptive decisions, yet different forms of exploration serve different functions. Using experimental anxiety induction, computational modelling, and fMRI, we show that acute anxiety does not increase all exploratory behaviour uniformly. Instead, it selectively boosts random, value-free exploration, choices driven by noise rather than information seeking, while leaving goal-directed, novelty-driven exploration unchanged. This shift reflects altered engagement of frontoparietal brain regions involved in control and uncertainty processing. These findings highlight a specific computational pathway through which acute anxiety disrupts decision-making, offering mechanistic insight relevant to both basic neuroscience and anxiety-related disorders.