Motor control

Importance of motor control

• All of the “cognition” that we’re interested in must end in behavior—movement.

• Brain terrain– Where is it/where do I want it to be?– What do I want to do with it?– Get the body to move it.

Cortical motor structures

AbstractPlanning

Spatial stuff for move-ment

somatosensation

Eye movementsMotorPlanning

Planning

Execution

Hierarchy: planning & execution

Comparison of motor planning and execution

Planning AND Execution

Comparison of motor planning and execution

Execution but minimal planning

Comparison of motor planning and execution

Planning but no execution

Can lower level of hierarchy operate without the higher?

The ability can be impressive

• Stuff that your body is ready to do such as reflexes, & biases to the system

• Planned control (which can usually overcome these biases, if necessary)

• Movement is usually a product of both

2 types of control

Demonstration of biases

• Fingers—move in phase

• Hands move in phase

NOTE that this implies that control is about trajectories

You get these oddities because you have biases in the trajectories of

movements

Evidence for trajectories

Monkey must move two jointed arm to a lighted target

A single neuron

Summary of many neurons

Each line = 1 neuron:direction = preferred directionlength = vigor of firing

Summary

These data indicate that movement is coded in terms of directions.

But other data indicate it is in terms of endpoints

Polit & Bizzi

Traditional models

More recent model

Trajectory (space)

Endpoint (muscle)

Sequencing

Hierarchical representation of action sequence

• Complex actions– Serving a tennis ball– Playing the piano

• Are these actions simply constructed by linking independent movements? Or are they guided by hierarchical representational structures that govern the entire sequence?

Serve

toss hit Follow through

Muscle actions

Cognitive

Hierarchical representation of action sequence

• Some aspects of motor learning are independent of the muscular system used to perform the actions.

• Motor representations are not linked to particular effector systems.

• Handwriting example.

Hierarchical representation of action sequence

• Peter Vidman Olympic gymnast said:

• “As I approach the apparatus…the only thing I am thinking about is…the first trick…. Then, my body takes over and hopefully everything becomes automatic….”

Just go. . . .

Pete Sampras, not serving

Perceptual motor integration

Can you just “run” one of these programs?

Or do you need perceptual feedback as you go?

Peripheral control of movement and the role of feedback

Perceptual motor integration

Some simple movements can be made without feedback, but usually the movement is much more effective with feedback.

Think of walking down a hallway with your eyes closed.

Try writing your name with your eyes closed

Perceptual motor integration

Proprioception--feeling from skin, joint receptors, and muscle receptors, that tells you where your limbs are.

Proprioception is important because knowledge of limbs location is important for egocentric space.

Motor skill learning

Fitts’s stage theorySchmidt’s schema theoryWillingham’s COBALT

Fitts’s stage theory

Cognitive--conscious, think of rules, basic strategies

Associative--unconscious, hook up of stim & resp

Autonomous--stim & resp are well represented, and verbal representation drops out.

Schmidt’s schema theory

Generalized motor program: one that can produce a whole class of movements; e.g., swinging a bat, swinging a racquet, throwing a ball.

Analogy: regression

0

20

40

60

80

100

0 2 4 6 8 10Arm position

Advantage of theory: it can account for the flexibility of motor behaviors.

Disadvantage: the data to support it aren’t that strong.

COBALT

COntrol BAsed Learning TheoryBasic premise: motor skill grows directly out of processes that support motor control.

Where is it/where do I want it to be? (perceptual-motor integration, sequencing)What do I want to do with it? (strategic)Get the body to move it. (dynamic)

Strategic: deciding what to doPerceptual-motor integration: selecting spatial targetsSequencing: assembling the sequence of spatial targetsDynamic: translating targets into pattern of musclemovements.

Goal to change theenvironment

Select spatial targetfor movement

Assemble sequenceof spatial targets

Pattern of muscleactivation

Goal to change theenvironment

Select spatial targetfor movement

Assemble sequenceof spatial targets

Pattern of muscleactivation

Strategicprocess

Strategicprocess

In addition, there are two modes in whichmovements can be expressed: conscious & unconscious.

What makes this model different

• It is a neuropsych model, with proposals for the neural bases of all of these processes

• It emphasizes that conscious knowledge can be useful at any time during training, not just early.

• Automaticity occurs through the parallel development of conscious & unconscious knowledge.

• Accounts for choking.