Social marketing intervention for social media-related adolescent risk behaviours in North India: A multi-city cluster RCT protocol.

Behavior has been defined as the total movement produced by an animal (). Learned movement sequences, in particular, involve repeated execution of actions with high precision, low variability, and speed. Despite fine-scale dissections of the brain areas that may contribute to movement generation—including neural circuits in the cortex and basal ganglia (BG) (–), the roles of different neural structures in producing movements, and whether these roles generalize across movement types, remain unresolved (). The dorsal striatum, the major input structure of the BG, is widely implicated in the learning and execution of procedural skills (–). Striatal neural activity correlates strongly with behavioral events during procedural tasks and changes with learning (–). Proposed roles of the striatum include action selection (–), encoding kinematic parameters of movements (, ), controlling movement vigor (i.e., speed and force) (, –), and storing or chunking motor sequences when behaviors become automatic (, , ). Although striatal spikes have been functionally correlated with various behaviors, the extent to which they influence movement execution remains elusive—particularly whether they contribute moment-to-moment, and whether any movement phase or type exists where they are dispensable. Furthermore, prior work using lesions or perturbations has typically focused either on precisely controlled forelimb movements (, , , –) or on whole-body locomotion (, , , ) but rarely on both within the same study. Whether striatal activity contributes uniformly across movement types therefore remains unclear. To fill this gap, we performed striatal optogenetic inhibition across multiple phases of a procedural task involving both forelimb and whole-body movements: a simple reaction time (SRT) task in which rats performed a conditioned, tone-cued lever release for reward (, , ). Rats pressed and held a lever, released it upon hearing a trigger tone, and then made a whole-body locomotor movement (including turning) to the reward port on the opposite wall, followed by an operant nose poke for water—both forelimb and whole-body movements being learned operant responses chained into a motor sequence. We first characterized how these movement types were represented in the dorsolateral striatum (DLS) using chronic multisite recordings, including Neuropixels probes; we then optogenetically activated inhibitory interneurons to suppress striatal projection neurons and examined how behavior-coupled DLS photoinhibition affected movement initiation and execution; last, recording from the substantia nigra pars reticulata (SNr), a BG output nucleus, during DLS photoinhibition let us link these behavioral effects to changes in SNr activity. Our results show that event-coupled DLS spikes influence execution of both forelimb and whole-body movements—delaying or interrupting forelimb actions and producing slower, less efficient whole-body locomotion—whereas comparable dorsomedial striatum (DMS) perturbations have only minor effects.