Motor implementation of control and reward-based urgency regulation across impulsivity

Everyday decisions unfold dynamically, with commitment shaped by a growing sense of urgency that can, when excessive, contribute to impulsive choices. Here we aimed at dissociating two modes of urgency regulation, control-driven (accuracy-oriented) and reward-driven (motivation-based), and asked whether their relative influence varies across individuals differing in impulsivity. We further investigated how these regulatory modes are implemented in the motor system, focusing on two modulatory effects: surround inhibition and broad modulation. Healthy participants, whose impulsivity was assessed with the UPPS urgency dimension, performed a modified Tokens task crossing control demands (low vs high control blocks) with motivational context (low vs high reward trials). In two separate sessions, single-pulse TMS was applied either over the hand motor representation to probe corticospinal excitability indexing surround inhibition, or over the leg representation to index broad modulations of motor activity. This design successfully dissociated the two regulatory modes: control-driven adjustments (across blocks) were most evident in less impulsive participants, whereas reward-driven adjustments (across trials) were most evident in more impulsive participants. Consistent with this dissociation, control-driven urgency regulation was associated with broad modulation of motor activity, whereas reward-driven urgency adjustments were associated with changes in surround inhibition. These motor signatures may serve as probes of the respective contributions of control- and reward-driven regulation even when they are not explicitly dissociated. Our findings suggest that impulsivity may not simply reflect "more urgency" but a different weighting of the influences that shape it during decision making, a hypothesis that can now be tested in clinical conditions.