Nigro-Thalamic Projection Controls Timing of Action Initiation

The nigro-thalamic pathway is one of the main outputs from the basal ganglia, known to be involved in action selection, learning motor skills, and/or control the vigor of actions. However, the specific function of the nigral input to the motor thalamus remains unclear. Using a combination of in vivo electrophysiological recordings from motor thalamic neurons and optogenetic activation of nigral inputs in behaving head-fixed mice, we determined that this pathway is primarily involved in the proper timing of the release of goal directed actions. At the behavioral level, we were able to reduce the amount of impulsive licking by activating thalamic terminals. We describe changes in thalamic neuronal activity explaining this effect and propose a parsimonious model to account for our observations. These results provide new insight in the circuitry for timing control, a critical part of motor planning, and reveal a potential new target to modulate impulsivity.