Fig. 20.

Schematic overview of different types of motor learning. A: Motor adaptation. Starting with a well-established skill (pre), the learner is confronted with a modified environment that induces abrupt mismatch between the actual and the necessary execution (per). This leads immediately to high errors that decline relatively fast in a monotonic fashion back to baseline. When the environmental perturbation is removed, the learner continues with the adapted behavior that leads to errors in the opposite direction (after-effects, post). These errors decline rapidly back to baseline. The overall gain in skill is zero. B: Assisted adaptation. Starting with impaired performance (pre), an assistive device such as an orthosis or a cane, can improve behavior almost immediately due to its mechanical support (per). However, removing the device leads almost no after-effects as the learner has not adapted its unassisted behavior. C: Skill acquisition and retention. Starting with a lack of proficiency (pre), the learner gradually acquires the sensorimotor skill, reducing the error to a low level (per). This acquired skill tends to be retained for a long time (post). D: Acquisition and intervention. The time course and level of proficiency of the acquired skill can be enhanced by suitable interventions, both in therapy and healthy skill acquisition. Appropriate practice conditions and training schedule can lead to long-term retention of the enhanced skill.