Investigating the role of the human pgACC in cost-benefit decision-making using transcranial ultrasound stimulation

Balancing costs and benefits is a fundamental aspect of adaptive decision-making. The pregenual anterior cingulate cortex (pgACC) has been implicated in integrating costs and benefits to guide approach and avoidance behaviours (Amemori & Graybiel, 2012; Kable & Glimcher, 2007; Friedman et al., 2015). However, causal evidence for its role in human cost-benefit arbitration remains limited, despite its clear relevance for people with apathy or anhedonia. Here, we investigated whether transcranial ultrasound stimulation (TUS) of the pgACC modulates reward-effort trade-offs in humans.

Twenty-four participants performed a reward-effort decision-making task following TUS applied to the pgACC or a pgACC-unrelated white-matter control site in a within-subjects design. On each trial, participants decided whether to exert physical effort via a handheld dynamometer to gain rewards in an approach condition, or avoid losses in an avoidance condition. Reward or loss magnitude and required effort were varied trial-wise to assess cost-benefit trade-offs.

Participants’ choices were sensitive to both effort cost and outcome magnitude, with higher acceptance for larger outcomes and lower effort demands. Compared with control stimulation, pgACC TUS reduced acceptance rates, indicating reduced willingness to exert effort to avoid losses. This effect was strongest for high-conflict trials near participants’ indifference boundaries, where preferences are most malleable.

These findings suggest that TUS to the human pgACC can influence cost-benefit decision-making. Reduction in acceptance rates indicate that pgACC stimulation may shift how effort costs and outcome benefits are integrated during action selection. This provides a framework for using TUS to investigate motivational circuits with potential relevance to apathy and anhedonia.