Dissociable contributions of motor-execution and action-observation to intramanual transfer.

We examined the hypothesis that different processes and representations are associated with the learning of a movement sequence through motor-execution and action-observation. Following a pre-test in which participants attempted to achieve an absolute, and relative, time goal in a sequential goal-directed aiming movement, participants received either physical or observational practice with feedback. Post-test performance indicated that motor-execution and action-observation participants learned equally well. Participants then transferred to conditions where the gain between the limb movements and their visual consequences were manipulated. Under both bigger and smaller transfer conditions, motor-execution and action-observation participants exhibited similar intramanual transfer of absolute timing. However, participants in the action-observation group exhibited superior transfer of relative timing than the motor-execution group. These findings suggest that learning via action-observation is underpinned by a visual-spatial representation, while learning via motor-execution depends more on specific force-time planning (feed forward) and afferent processing associated with sensorimotor feedback. These behavioural effects are discussed with reference to neural processes associated with striatum, cerebellum and motor cortical regions (pre-motor cortex; SMA; pre-SMA).