The natural variability of a dexterous motor skill is stably encoded in the cortex of freely behaving mice

Skilled, goal-directed movements can exhibit trial-to-trial variability even in experts, particularly in response to dynamic environmental conditions or when perfect repetition is not required for success. Identifying where, to what extent, and how stably this variability is encoded in the nervous system will yield insight into how such learned movements are robustly maintained over time yet flexibly executed on each trial. We record calcium fluorescence activity in motor cortex--a key node in the multi-areal network responsible for movement control--in freely-moving mice performing a self-paced, precision reach-to-grasp task. High trial counts and rich single-trial variability enable rigorous statistical analysis of moment-to-moment movement encoding across matched behavioral sets over five days. We found that individual neurons in motor cortex stably encode details of paw, digit, and head movements, suggesting that reliable contributions from single cells support the consistent execution of skilled movements over time, even in complex, sensory-guided tasks like reach-to-grasp.