Motor Control Theory 1

Motor Control TheoryDynamic & EcologicalApproaches(Large parts adapted from Wallace, 1993)

Asking the right question/questionsHow do we move the way we do?Seeks one solutionA causal influenceTends to emphasize neural solutions Tends to lead to hypothetical constructs to achieve solutions where neural solutions are not knownTends to shape ones thinking of control as a hierarchy

Asking the right question/questionsWhy do we move the way we do?A different focusTends to make us look at all possible influences on the shape of movementDoes not seek one solution, but accepts many simultaneouslyTends to shape ones thinking of control as a heterarchy This is the way well be approaching the problem

A heterarchical theory of controlOr theories...Complex systems theoryDynamic pattern perspective & synergeticsEcological psychologyAll have in common the tendency to ask why rather than howThe study of relationships among things, rather than the things themselvesLeads to the study of...

A heterarchical theory of controlConstraints...Things which limit our range of movements thus shaping them...and affordancesThings which permit (or even suggest) certain methods of movement or interaction with an object

A heterarchical theory of controlSurface typeLightingVisual flowSpeed/accuracy requirementsNumber of tasksstandingseatedmovingSensory lossCognitionFlexibilityStrength/powerCardiovascularEnvironmental ConstraintsIndividual CapabilitiesTask Demands3 categories of constraint (+ examples)Motor abilitiesEnvironmental stabilityFrom Newell (1986)

A heterarchical theory of controlProcesses in coordination dynamicsDynamics of CNS(neural level)Dynamics of action system(effector level)Dynamics of environment(environmental level)ConnectionismAction system theoryLaws of perceiving and acting (ecological psychology)Coordination dynamicsFrom Schmidt & Fitzpatrick (1993)

An example (physical world)Systems far from equilibrium

There are no instructions determining the pattern of behavior just elements of the system interactingBut this isnt very complexEquilibriumClosed systemPunch hole in containerOpen systemFar from equilibrium

Listen to this firstthen this

A more complex exampleThe Benard instability (Prigogine & Stengers, 1984)

Again, the system self-organizes to these patternsHeat is a control parameter (this forces the system to change its organization)(hexagon: from temp gradient + descent of cool molecules via gravity)heatA pan of about 1cm depth of oilMore heat

randomhexagonalturbulence

A more complex exampleThe Benard instability (Prigogine & Stengers, 1984)

Note that each pattern does change, but it resists change also a property known as stabilityStability and loss of stability are central to dynamic pattern theoryheatMore heat

randomhexagonalturbulentA pan of about 1cm depth of oil

Pause, consider, then move onGetting too big have to break down into multiple slide sets