Movement refinement and cholinergic regulation of outcome-dependent updating during skilled reaching.

In mice performing single-pellet skilled reaching, movement refinement improved targeting and retrieval and increased trajectory consistency, while grasp success after pellet contact did not change detectably.

• Why it matters: Conventional success metrics can hide which action components improve with practice versus how recent outcomes reshape subsequent execution.
• What they did: The study combined detailed outcome scoring with kinematic stage decomposition across training, while monitoring acetylcholine in vivo and inhibiting striatal cholinergic interneurons during training.
• The result: Acetylcholine rose before reach onset and declined during execution without early-to-late training differences; cholinergic interneuron inhibition left refinement largely intact but altered outcome-dependent updating, especially after grasp-then-loss trials.

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