Distinct Kinematic Adjustments over Multiple Timescales Accompany Locomotor Skill Development in Mice.

Robust locomotion is critical to many species' survival, yet the mechanisms by which efficient locomotion is learned and maintained are poorly understood. In mice, a common paradigm for assaying locomotor learning is the rotarod task, in which mice learn to maintain balance atop of an accelerating rod. However, the standard metric for learning in this task is improvements in latency to fall, which gives little insight into the rich kinematic adjustments that accompany locomotor learning. In this study, we developed a rotarod-like task called the RotaWheel in which changes in paw kinematics are tracked using high-speed cameras as mice learn to stay atop an accelerating wheel. Using this device, we found that learning was accompanied by stereotyped progressions of paw kinematics that correlated with early, intermediate, and late stages of performance. Within the first day, mice sharpened their interlimb coordination using a timed pause in the forward swing of their forepaws. Over the next several days, mice reduced their stride length and took shorter, quicker steps. By the second week of training, mice began to use a more variable locomotor strategy, where consecutive overshoots or undershoots in strides were selected across paws to drive forward and backward exploration of the wheel. Collectively, our results suggest that mouse locomotor learning occurs through multiple mechanisms evolving over separate time courses and involving distinct corrective actions. These data provide insights into the kinematic strategies that accompany locomotor learning and establish an experimental platform for studying locomotor skill learning in mice.