Striatal modulation supports context-specific reinforcement and not action selection

Two models dominate our grasp of how the basal ganglia influence behavior: action selection and reinforcement learning. Studies applying prolonged stimulation to striatal projection neurons provide foundational evidence for the gating of actions; however, this approach ignores the inherent brief, movement-aligned dynamics that characterize these cells. To determine how striatal subpopulations contribute to mouse behavior, we increased striatal activity transiently and in action contexts that directly dissociated the contrasting models: upon the detection of locomotor arrest or turns. Action selection models dictate that increasing direct pathway activity will induce the selection of locomotion and contralateral turning. Instead, context-selective stimulation biased mice toward more frequent locomotor arrest and leftward turns, regardless of the side of stimulation. Indirect pathway stimulation had the opposite effect. These results reveal that the striatum acts to modulate behavior independent of the type of action, providing a mechanism to shape a wide range of behavioral dynamics.