Wednesday October 15, 2003
John Milton
University of Chicago
Abstract:Neural motor control mechanisms are frequently tuned at the edge of stability. Examples arise in the control of saccadic eye movements and bimanual limb movements. However the advantages offered by this control strategy, if any, are presently unclear. A recently emphasized paradigm for the acquisition of motor skill is stick balancing at the fingertip. Motion analysis in three dimensions demonstrates that the fluctuations in the vertical displacement angle of a stick balanced at the fingertip obey a power law characteristic of on-off intermittency. The presence of on-off intermittency implies that the control mechanism is tuned close to a stability boundary and that an important control parameter is being stochastically or chaotically forced across this boundary. Measurements of the development of balancing skill together with considerations of stick balancing as a survival time problem suggest that tuning neural control at the edge of stability provides: 1) a mechanism so that corrective movements can be made faster than the delay; and 2) a mechanism to minimize the need for consciously directed control movements. These observations strongly resonate with recent functional magnetic resonance imaging studies of novice and professional golfers that indicate that the "road to automatic" for motor skill acquisition involves a changes in both the motor and consciousness/emotional control systems of the brain.
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