John Krakauer, Ph.D.
Center for Functional Recovery After Brain Injury,
The Johns Hopkins Hospital
December 6, 2010
Rethinking Motor Adaptation and Motor Skill
The precisely executed axel jump of the champion figure skater, the rapidly moving fast ball and the well-timed interception in football are all athletic maneuvers requiring near perfect execution of form to attain a result. In many ways, the sports arena greatly exemplifies the relationship between form and function. How motor skills are acquired, and when lost, potentially relearned, was the subject of Dr. John Krakauer's talk when he visited Brandeis for our M.R. Bauer Colloquium series.
Society often seems to reward motor skill above everything else, at least judging by the salaries of professional athletes. Conversely, loss of motor function caused by neurological injury and disease carries immense cost to individuals and society. Both attainment of high levels of skill, and the rehabilitation of lost skills, depend on motor learning, which makes the study of motor learning of great scientific and practical interest.
Adaptation is a process by which systematic errors introduced by perturbations are reduced by updating a forward model to close prediction errors. Motor adaptation is dependent upon a brain structure known as the cerebellum and has been shown to be both an implicit and often reward-indifferent behavior. Through the combined use of a battery of techniques, including quantitative motion analysis, structural and functional imaging, non-invasive brain stimulation and robotics, Dr. Krakauer's work argues that other learning processes are involved in motor learning in addition to adaptation. These processes include: (1) use-dependent plasticity, which leads to the directional biases often observed in motor skills following adaptation, and (2) operant reinforcement-biases, which are often seen when adaptation is associated with successful error reduction. Work from the Krakauer lab suggests that this operant reinforcement is the process that underlies not only the ability to learn but also to relearn or unlearn a given motor skill. By generating models of how motor commands are translated into sensory consequences, the Krakauer lab hopes to better understand ways in which consistent and coordinated movements are produced in the face of environmental variability and changes in one's internal state.