Mechanism underlying dopamine’s distinct effects on movement vigor versus action timing in basal ganglia

Determine whether the distinction between dopamine’s modulation of movement vigor and its influence on the temporal placement of action transitions in basal ganglia circuits arises from dissociable effects of dopamine on overall striatal activity levels versus effects on the temporal evolution (speed) of striatal population activity.

Background

The basal ganglia (BG) are proposed to learn and regulate discrete action policies, integrating state and action representations from cortex with dopaminergic reward-related teaching signals. Evidence suggests that BG activity influences the timing of discrete transitions between actions via temporal scaling of striatal population dynamics, while movement vigor is modulated by overall activity levels (e.g., direct-pathway medium spiny neurons).

Recent experiments manipulating striatal temperature demonstrated causal effects on animals’ categorical timing judgments without corresponding monotonic effects on movement kinematics, supporting a division between discrete action timing and continuous movement vigor within BG. The authors highlight an unresolved question regarding whether this division reflects distinct dopaminergic mechanisms acting on striatal activity levels versus its temporal evolution.