Transcript Motor control

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
Motor
Eye movements Planning
somatosensation
Spatial
stuff for
movement
Abstract
Planning
Hierarchy: planning & execution
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
2 types of control
• 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
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 direction
length = 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
Cognitive
Follow through
Muscle actions
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 theory
Schmidt’s schema theory
Willingham’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
100
80
60
40
20
0
0
2
4
6
8
A rm positi on
10
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 Theory
Basic 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 do
Perceptual-motor integration: selecting spatial targets
Sequencing: assembling the sequence of spatial targets
Dynamic: translating targets into pattern of muscle
movements.
In addition, there are two modes in which
movements can be expressed: conscious &
unconscious.
Strategic
process
Goal to change the
environment
Select spatial target
for movement
Assemble sequence
of spatial targets
Pattern of muscle
activation
Strategic
process
Goal to change the
environment
Select spatial target
for movement
Assemble sequence
of spatial targets
Pattern of muscle
activation
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.