Urgency tunes corticospinal excitability in a center-surround way during action selection

Abstract Decision making and action selection is part of our daily life as our environment provides us with many potential actions. Adjusting the time invested in deciding and moving is key to have the highest reward rate possible. The aim of the present study was to investigate the decision-making mechanisms, moreover the impact of urgency on the motor representations of three muscles in both hands during action selection. A total of 50 healthy participants realized a modified version of the “Tokens task” in which evidence for between-hand choices dynamically changed over time within each trial. Incorrect responses were associated with either a low or a high penalty, as reward dropped over time producing an increasing sense of urgency over the course of a trial and a higher urge to respond. TMS allowed us to probe online changes in corticospinal excitability (CSE) at four different timings and characterize the impact of urgency on neural activity. With a high urgency, subjects made fast, less accurate and audacious decisions. The CSE of all muscles (selected or not) increased over time. At the last TMS timing, CSE was higher for the task-related muscle in the higher urgency block. Our results show a global increase of CSE in both hand’s muscles. We suggest that the increase in urgency induced a boost of the center-surround inhibition mechanism within the M1 in the selected hand. We argue whether the basal ganglia or the Locus coeruleus or more lateral inhibition could generate such results.