Chapter 5
Motor Control Theories
Concept: Theories about how we control coordinated
movement differ in terms of the roles of central and
environmental features of a control system
Theory and
Professional Practice
 What is theory?
• Accurately describes a large class of
observations
• Make definite predictions about results of
future observations (Hawking, 1996)
 With motor learning and control,
theories focus on:
• Explaining human behavior
• Providing explanations about why people
perform skills as they do
• Identifying variables through observations
of these performances
THEORY (Miller, 1983)
 A theory is a set of interconnected
statements that describe
UNOBSERVABLE structures or
processes and relate them to each
other and to unobservable invents.
Theory gives meaning to facts, just
as a blueprint provides the structure
that transforms stones into a house
Motor Control Theory
 Describes and explains how the
nervous system produces
coordinated movement of motor
skill in a variety of environments
 Two issues of importance:
• Coordination
• Degrees of freedom
Coordination
 Patterning of body and limb motions
relative to the patterning of
environmental objects and events
(Turvey, 1990)
 Two parts to consider:
• Movement pattern of a skill in relationship
at a specific point of time
• Context of the environment of the head,
body, and/or limb movements so the actions
can be accomplished
Degrees of Freedom
 Number of independent elements in a
central system and the ways each
component can act
 Degree of Freedom problem:
• Control problem
• Occurs in the designing of a complex
system that produces a specific result
• Involves determining how many degrees of
freedom is required to produce the result
DF definition
 Latitude of variation a statistical
system has
Two numbers have to add to 100 and
one number is known = one DF
DF the number of separate,
independent dimension of movement
in a system that has to be controlled
Nicolai Bernstein
 100 joints and 792 muscles
 System has to act in a specific way
 Large number od DF if different
positions and speeds are needed for
specific movement execution
Theory of Motor Control
 FLEXIBILITY
 UNIQUENESS
 CONSISTENCY
 MODIFIABILITY
FLEXIBILTY
- Many ways to achieve the movement
goal.
- Using variety of muscular resourses
UNIQUENESS
- A LARGE NUMBER OF
VARIABLES INFLUENCE EACH
MOVEMENT
- MAKING IDENTICAL
MOVEMENT IS IMPOSSIBLE
MODIFIABILITY
 ABILITY TO ALTER A
MOVEMENT DURING ITS
PERFORMANCE
 SAFETY
 CREATIVITY
CONSISTENCY
 ABILITY TO PERFORM THE
TASK AS CLOSE TO THE
TARGET AS POSSIBLE
 TASK REPRODUCTION
Theories in Clinical Practice
 Theory helps to interpret the
behavior and allows the therapist to
go beyond one patient
 Framework for Behavioral
Interpretation
Case study
 Case: After a cerebral-vascular
accident, a patient has flexed left
arm at the elbow and uses toe-heel
gate pattern
 Theory: Reflex theory: abnormal
reflexes (spasticity) are a major
reason for patient’s dysfunction
Case study - Assumptions
 Normal movement emerges as an
interaction among many control
systems
 Movement is organized around a
behavioral goal and in constrained
by the environment
 Interaction with environment leads
to predictive and adaptive behavior
Guide for Clinical Action
 Malfunction is a result of
compensation for a deficiency of
control systems
 CNS causes a release of abnormal
reflexes, normally organized at
lower level of CNS
Cont…
 Lesions in Motor cortex result in
dysfunction
 Lesions may release control of
lower control centers – primitive
pathological behavior may emerge
Motor Control Theories
 Reflex theory
 Hierarchical theories
 Dynamic systems theories
Reflex Theories
 Behaviour is explained by
stereotype, involuntary responses to
stimuli
 Habits are developed through
conditioning
 A stimulus elicits the response as a
result of practice
Hierarchical Theories
 Brain orchestrates lower levels of





CNS
Executive level
Effector level
Open loop
Closed loop
Generalized Motor Program
Open Loop and
Closed Loop Systems
 Models of basic descriptions that show
the CNS and PNS initiate and control
action
 Each has a central executive
 Executive generates and issues
movement instructions to effectors
(muscles/joints)
 Both also contain movement instructions
from control center to effectors
Differences Between
the Systems
 Two differences
Open Loop
Closed Loop
 Does not use
 Uses feedback
 Control center
feedback
 Control center
provides all the
information for
effectors to carry
out movement
issues information
to effectors
sufficient only to
initiate movement
Adams’ Closed Loop Theory
 Memory Trace
 Perceptual trace
-produces movement
-modest MP
-selects action
-shove towards the
target
-reference mechanism
of correctness
-memory of past
movements
-responsible for
movement in progress
-PT is developed by
practice
Adams’ predictions
 Interference with KR degrades
learning
 Errors decrease with KR
 Degrading quality of perceptual
feedback retards development of PT
 Errors are damaging to PT
Two Theories of
Motor Control
1.
2.
Motor Program-based theory:
memory-based construct that controls
coordinated movement
Dynamic Pattern theory, a.k.a.
Dynamic Systems: approach to
describing and explaining the control
of coordinated movement that
emphasize the role of information in
the environment and properties of the
body/limbs
MP Definitions
 1890, William James: idea of motor
action, clear image of the action
 1960, Franklin Henry: neural
pattern of movement is controlled
by a stored program, which is used
to direct the motoneuron detail of
motor performance
MP
 1968, Steven Keele: MP is a set of
commands that are structured
before a movement sequence begins
and that allow the entire sequence
to be carried out without influence
of peripheral feedback.
MP, cont…
 1971, R. Schmidt: A motor program
whose expression can be varied
depending in the choice of certain
parameters.
-contains advanced instruction sequence and timing
-no capacity to correct errors
MP is effective in the stable,
predictable conditions
Schema theory
 Schema is a set of rules that guide
production of goal oriented
movement
 After movement is performed, the
info about the movement is
abstracted in four general areas
General memory areas
 Environmental condition at the
beginning of the movement
 The specific requirement of the
movement speed, force..)
 The outcome of the movement and
KR (comparison of the actual and
intended outcome)
 Sensory consequences
Schema theory predictions
 Performer can perform a new
movement of learned skill in novel
situation
 Practice improves ability to make
new movements
 Increase variety of practice
contributes to a better experience
with parameters
Motor Program-Based
Theory
 Based on the work of Richard
Schmidt (1988)
 Hypothesized generalized motor
program: mechanism accounting for
adaptive and flexible qualities of
human movement
 Proposed that generalized motor
program controls class of actions
vs. specific movement
Motor Program-Based
Theory, cont’d
 These “invariant factors” are the
signatures of the generalized motor
program (does not vary from one
performance to another)
 Parameters are specific movement
features that can vary from one
performance of a skill to another
Class of actions
 Class of actions is controlled by
“Invariant characteristics”:
Relative timing and relative force.
 Variant characteristics, Parameters:
muscle involved, overall force, and
duration are added to movement
Steps in movement
organization
 Response selection
 Retrieve MP form LTM
 In the response programing stage
add parameters
 Temporal pattern and relative force
stay the same
Schmidt’s Schema Theory
 Schema: rules that serve to provide
the basis for a decision based from
related experiences
 Described two control components:
• Generalized motor program – control
mechanism responsible for controlling
a class of actions, i.e., kicking
• Motor response schema – responsible
for providing the specific rules
governing an action in a given situation
Schmidt’s Schema Theory, cont’d
 This theory explains how a person
can adapt to new situations or
environmental contexts
 Solves the degree of freedom
problem
Dynamic Pattern Theory
(a.k.a., Dynamical Systems)
 Describes the control of coordinated
movement that emphasizes the role
of information in the environment
and dynamic properties of the
body/limbs
 Seen from the perspective of
nonlinear dynamics (behavioral
changes are abrupt)
Stability and Attractors
 Stability: behavioral steady state of
a system
 Attractors: stable behavioral steady
states of systems
• Preferred behavioral states
• Energy efficient states
Order and
Control Parameters
 Order parameters, called collective
variables
• Functional specific and abstract variables
that define the overall behavior of the system
• Enable a coordinated pattern of movement
that can be reproduced and distinguished
from other patterns
Collective Variables
Rhythmic Movements:
Relative phase is the most prominent of order
parameters which represents the movement
relationship between two movement segments
Aiming Movements:
Equilibrium Point
Order and
Control Parameters, cont’d
 Control parameter
• Variable, when increased or
decreased, will influence the stability
and character of the order parameter
• Is important to identify since it
becomes the variable to manipulate in
order to assess the stability of the order
parameter
• Provides the basis for determining
attractor states for patterns of limb
movement
Control parameters
 Control parameters (speed and
force) change freely according to
situation.
 In research, the Control parameters
are systematically changed and
Collective variables are measured
Order and
Control Parameters, cont’d
 Self-Organization
• When certain conditions characterize
a situation, a specific pattern of limb
movement emerges
• This pattern of movement selforganizes within the characteristic of
environmental conditions and limb
dynamics
Coordinated Structures
 Functional synergies of muscles and
joints of a person’s nervous system
which act cooperatively to produce
an action
 Develops through practice,
experience, or naturally
 Can be intrinsic (walking) or
developed through practice
Perception and
Action Coupling
 Dynamic pattern theory
 Essential element in accounting for
skillful performance of open skills
 The perception part of the
interaction detects and uses critical
invariant information in the
environment
Perception and
Action Coupling, cont’d
 The action part involves the setting
and regulating of movement control
features that enable action goal
achievement
 For example, Greek letter “tau” ()
 Perceptual variable “tau” couples
with dynamic movement
Present State of the
Control Theory Issue
 Motor program-based theory and
dynamic pattern theory are the
predominant behavioral theories
addressing how the nervous system
produces coordinated movement
 Theory of control cannot focus
exclusively on the movement
information that is specified by the CNS
Present State of the
Control Theory Issue, cont’d
 Task and environmental
characteristics must be taken into
account (Newell, 1986)
 Speculation of hybrid on a
compromise theory could emerge,
to explain the control of
coordinated movement
Chapter 5
Motor Control Theories