The degrees of freedom problem in postural control
Kilby, Melissa Christine
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This dissertation tackled a longstanding, yet unresolved problem in the motor control literature known as the degrees of freedom problem (Bernstein, 1967). Two experiments were setup to study the redundancy and collective variable(s) of the complex postural control system at the behavioral level. To this aim postural control mechanisms were studied under a variety of environmental and intrinsic constraints to posture such as increasing the task difficulty (standing on one leg) or channeling sensory information to visual processing via augmented real-time biofeedback. The overall goal was to identify the dimension of functional synergies and candidate collective variables from a dynamical system's point of view. Using multivariate statistical methods (canonical correlation analysis) this dissertation provided further evidence for varying degrees of multi-link postural control strategies and identified the COP-COM coupling relationship as a potential collective variable which organizes and harnesses the system's behavior.