Altered basal ganglia output during self-restraint.

Suppressing actions is essential for flexible behavior. Multiple neural circuits involved in behavioral inhibition converge upon a key basal ganglia output nucleus, the substantia nigra pars reticulata (SNr). To examine how changes in basal ganglia output contribute to self-restraint, we recorded SNr neurons during a proactive behavioral inhibition task. Rats responded to <i>Go!</i> cues with rapid leftward or rightward movements, but also prepared to cancel one of these movement directions on trials when a <i>Stop!</i> cue might occur. This action restraint - visible as direction-selective slowing of reaction times - altered both rates and patterns of SNr spiking. Overall firing rate was elevated before the <i>Go!</i> cue, and this effect was driven by a subpopulation of direction-selective SNr neurons. In neural state space, this corresponded to a shift away from the restrained movement. SNr neurons also showed more variable inter-spike intervals during proactive inhibition. This corresponded to more variable state-space trajectories, which may slow reaction times via reduced preparation to move. These findings open new perspectives on how basal ganglia dynamics contribute to movement preparation and cognitive control.