Motor implementation of context- and reward-based urgency regulation during action-oriented decision making

Action-oriented decisions are shaped by a sense of urgency, a state that builds as the need to commit to an action increases. When poorly regulated, this urgency may bias decisions toward impulsive choices. Because this urgency state may be influenced by different factors, we aimed to dissociate context- and reward-based sources of urgency state regulation. We determined how these regulatory modes are implemented in the motor system across healthy individuals whose impulsivity trait was assessed using the UPPS-P Impulsive Behavior Scale, with a focus on the urgency trait dimension. Participants (n=20, including 13 women) performed a left-or-right index-finger Tokens decision-making task in which contextual demands and reward prospect were orthogonally manipulated to isolate context- and reward-based urgency regulation, with single-pulse Transcranial Magnetic Stimulation (TMS) used to probe corticospinal excitability either in leg muscles, indexing broad modulation of motor activity, or in hand muscles, indexing surround inhibition, as candidate mechanisms underlying these regulatory modes. Our results indicate that context-based urgency state regulation is most evident in individuals with a lower urgency trait, whereas reward-based regulation is most prominent in those with a higher urgency trait. Both forms of regulation were associated with broad motor excitability changes, with reward-based regulation additionally associated with surround inhibition, suggesting that this signature mainly reflects reward prospect rather than urgency state. Based on our findings, urgency-related trait impulsivity may not simply reflect a persistently "higher state of urgency" but rather a different weighting of influences that shape it during decision making in the motor system.Significance statement By orthogonally manipulating contextual demands and reward prospect within a single action-oriented decision task, we show that urgency state regulation reflects multiple influences whose relative weighting varies with urgency-related impulsivity trait. Individuals with lower urgency trait primarily expressed context-based urgency regulation, whereas those with higher urgency trait showed stronger reward-based urgency regulation. TMS revealed complementary motor signatures: broad, non-selective changes in corticospinal excitability indexed global shifts in motor readiness that covaried both with context- and reward-based urgency regulation, while surround inhibition primarily tracked reward prospect as a value-related motor gain signature. Together, these results clarify how context and reward shape action commitment through shared and specific motor implementations.