Chapter 2

Part 2: Motor Control Chapter 5 Motor Control Theories

Do we decide how we move? Are you in control of your body? SureBut to what extent?To what degree are the movements you make strictly down to your choice? To what degree is choice an illusion?

What do we need to understand?How are intentions translated into action?What information guides movement?How does intention shape movement?How does learning one movement help in learning another?What is best practice in training/coaching movement skills?

What sort of problem are we facing?The problem of control is one of choices and variety 792 muscles, 100 joints. Thats a lot of decisions to make (degrees of freedom problem)We never make the same movement twice, but something is similar across repetitions of behaviorWe can learn

3.2.What sort of problem are we facing?degrees of freedom problemProblem for who?Car example how many steering wheels on a normal car?Constraints/affordances how are the wheels made free to vary? Axles joined together.Wheels of rear axle locked pointed in same direction

Front wheels can be turned using steering wheel

1.

What sort of problem are we facing?degrees of freedom problemCar example how many steering wheels on a normal car?What if you freed the rear axle too, so that youd have another steering wheel?How would it affect complexity of system control? How would it affect complexity of system output?How about if you freed all 4 wheels (so you had 4 steering wheels?Biological systems and degrees of freedome-coli bacteria vs. humans

1.2.

3.

4.

What sort of problem are we facing?The problem of control is one of choices and variety Redundancy (motor equivalence a good thing)In the car example, freeing the back wheels means you can steer in two different ways.Consciousness vs. controlWhen you write a word, what are you attending to?When you perform best at your chosen sport (or any other physical activity), what sort of stuff are you thinking about?

Making a start: A basic model2 streams of information:One out efference, output (e.g muscle contractions)One in afference, feedback (e.g. sight, sound, proprioception)But theyre both going on completely continuously, so breaking them down and focusing on one may be a mistakeOne theory (motor program theory) focuses on the out streamThe other (dynamic pattern theory, which well focus on) takes a more interactive approach, looking for properties within us and around us that may determine how movements (the patterns referred to) form

Making a start: A basic model Defn: feedback = sensory informationThe simplest control model:InputThis model uses OPEN-LOOP controlDef: Open-loop control = outgoing messages only. No feedbackProcessingOutput

Making a start: A basic model EffectorsThis model uses Closed-Loop controlDef: Closed-loop control = use of feedback to guide behaviorProcessingOutputFeedback (= input)

Making a start: A basic model Moving closer to realityHow many senses do you have?http://www.youtube.com/watch?v=CUn7zy8Ya20Each of these are sensory inputs (feedback)How many muscles/fibres/motor neurons do you have?Each of these are motor outputs (grouped, form effectors muscles or even limbs)William James (1891) & others careful observation...1.

2.

3.

Making a start: A basic modelThe reality...There are many studies that suggest the interaction between these two sources of information is in reality far more complex than simply one upstream (feedback) and one downstream (motor commands)The signals seem to interact at every available level of the system, resulting in a complexity of signal processing that is very dauntingSo whats the message behind this?

Making a start: the next stepNo final answer...(robotics, artificial intelligence, neuroscience etc...)So we need a theory that is one step removed from the final answerDynamic pattern theory works at every level of the system (neural, behavioral)It does a decent job of helping us to understand where movements come from