This article will involve three parts ,for the convenience of readers and better conceptual understanding i am simplifying by starting with the basic understanding of motor control and motor learning and this will be a revision of theory ,subsequent parts will focus on description of its application and recent research work.
What is Motor Control?
-An ability to regulate and direct the mechanisms essential to movement.
The process of initiating, directing, and grading purposeful voluntary movement".
So lets address how CNS organizes many individual muscles and joints in to coordinated functional pattern? or
How sensory information from body and environment is used to select and control movement?
Physical and Occupational therapists have been referred to as "Applied Motor Control Physiologist"(Brooks 1986) -because we spend considerable amount of time in understanding Motor control problems and as an occupational therapist our therapeutic strategies is directed in improving and retraining the functional movements & patterns.
The organization and production of movement is a complex problem, so the
study of motor control has been approached from a wide range of
disciplines, including psychology, cognitive science, bio-mechanics and
neuroscience.
The control of human movement has been described in many
different ways with many different models of Motor Control put forward
throughout the 19th & 20th Centuries. Motor Control Theories include
production of reflexive, automatic, adaptive, and voluntary movements
and the performance of efficient, coordinated, goal-directed movement
patterns which involve multiple body systems (input, output, and central
processing) and multiple levels within the nervous system
We will be understanding this in detail:
Let us focus on understanding of Movement:
its interaction of movement ,task and the environment
So organization of movement is constrained by factors
- Within Individual
- the task
- and environment
Within Individual factors that constrain Movement:
Movement and Action
Movement and Perception
Movement and Cognition
Task Constraints on Movement
Environmental constraints on Movement
Theories of Motor Control:
Readers can refer to Motor Control, Ann Shumway-Cook for detailed description:
| MOTOR CONTROL THEORIES
|
AUTHOR
|
DATE
|
PREMISE
|
CLINICAL IMPLICATIONS
|
| Reflex Theory
|
Sherrington
|
1906
|
- Movement is controlled by stimulus-response.
- Reflexes are basis for movement - Reflexes are combined into actions that create behavior.
|
- Use sensory input to control motor output
- Stimulate good reflexes
- Inhibit undesirable (primitive) reflexes
- Rely heavily on Feedback
|
| Dynamical Systems Theory
|
Bernstein
Turvey
Kelso & Tuller
Thelen
|
1967
1977
1984
1987
|
- Movement emerges to control degrees of freedom.
- Patterns of movements self-organize within the characteristics of
environmental conditions and the existing body systems of the
individual.
- Functional synergies are developed naturally through practice and
experience and help solve the problem of coordinating multiple muscles
and joint movements at once.
- De-emphasize commands from CNS in controlling movement and emphasize physical explanations for movement.
|
- Movement is an emergent property from the interaction of multiple elements.
- Understand the physical & dynamic properties of the body - i.e.
Velocity- important for dynamics of movement. May be good to encourage
faster movement in patients to produce momentum and therefore help weak
patients move with greater ease.
|
| Hierarchical Theories
|
Adams
|
1971
|
- Cortical centers control movement in a top-down manner throughout the nervous system.
- Closed-loop Mode: Sensory feedback is needed and used to control the movement.
- Voluntary movements initiated by “Will” (higher levels). Reflexive movements dominate only after CNS damage.
|
- Identify & prevent primitive reflexes
- Reduce hyperactive stretch
- Normalize tone
- Facilitate “normal” movement patterns
- Developmental Sequence
- Recapitulation
|
| Motor Program Theory
|
Schmidt
|
1976
|
- Adaptive, exible motor programs (MPs) and generalized motor
programs (GMPs) exist to control actions that have common
characteristics.
- Higher-level Motor Programs - Store rules for generating movements.
|
- Abnormal Movement - Not just reflexive, also including
abnormalities in central pattern generators or higher level motor
programs.
- Help patients relearn the correct rules for action
- Retrain movements important to functional task
- Do not just reeducate muscles in isolation
|
| Ecological Theories
|
Gibson & Pick
|
2000
|
- The person, the task, and the environment interact to in uence
motor behavior and learning. The interaction of the person with any
given environment provides perceptual information used to control
movement.
- The motivation to solve problems to accomplish a desired movement task goal facilitates learning.
|
- Help patient explore multiple ways in achieving functional task →
Discovering best solution for patient, given the set of limitations
|
| Systems Model
|
Shumway-Cook
|
2007
|
- Multiple body systems overlap to activate synergies for the
production of movements that are organized around functional goals.
- Considers interaction of the person with the environment.
- Goal-directed Behavior - Task Orientated
|
- Identifiable, functional tasks
- Practice under a variety of conditions
- Modify environmental contexts
|
Let's move to concept of Motor Learning
Motor learning is when complex processes in the brain occur in response
to practice or experience of a certain skill resulting in changes in the
central nervous system that allow for production of a new motor skill.
So ,Motor Control focuses on understanding of movement already acquired
Motor learning focuses on understanding the acquisition or modification of movement.
- Motor learning research often considers variables that contribute to
motor program formation (i.e., underlying skilled motor behaviour),
sensitivity of error-detection processes, and strength of movement
schemas. There are many different theories of Motor Learning
- Reference:Roller L et al, Contemporary Issues and
Theories of Motor Control, Motor Learning, and Neuroplasticity. In:
Neurological Rehabilitation 6th Edition. Mosby, 2012. p69 - 105.
Stages of Motor Learning
| Stages of Learning
|
Characteristics
|
Attention Demands
|
Activities
|
Description
|
| Cognitive
|
- Movements are slow, inconsistent and inefficient.
- Considerable cognitive activity is required.
|
- Attention to understand what must move to produce a specific result.
- Large parts of the movement are controlled consciously
|
Practise sessions are:
- performance focused
- less variable
- incorporate a clear mental image (technical & visual).
|
Early Cognitive;
Essential Elements were not observed or not present
|
Late Cognitive;
Essential elements are starting to appear
|
| Associative |
- Movements are more fluid, reliable and efficient
- Less cognitive activity is required
|
- Some parts of the movements are controlled consciously, some automatically.
|
- Practise sessions link performance and results, conditions can be varied.
- Clear Mental Image = Accurate Performance
|
Early Associative;
Essential elements appear, but not with consistency.
|
Late Associative;
Essential elements appear regulalry at a satisfactory level.
|
| Autonomous |
- Movements are accurate, consistent and efficient.
- Little or no cognitive activity is required.
|
- Movement is largely controlled automatically
- Attention can be focused on tactical choices
|
- Practise sessions are more results orientated
- Focus is on greater range of movement, speed, acceleration and use of skill in a novel situation.
|
Early Autonomous;
Essential elements appear frequently avove required level.
|
Late Autonomous;
Essential elements appear continuously at a superior level.
|
There are many different theories of Motor Learning.
| MOTOR LEARNING THEORY
|
AUTHOR
|
DATE
|
PREMISE
|
CLINICAL IMPLICATIONS
|
| Adams Closed Loop Theory
|
Adams
|
1971
|
- Closed Loop - Sensory feedback is used for the ongoing production of skilled movement
- Slow movements
- Relies on sensory feedback (Sherrington)
- Blocked Practice
- Errors = Bad! Needs to be accurate!
- Memory Trace - Initiation of movement
- Perceptual Trace - Built up over a period of practice & is the reference of correctness.
- Improvements = Increased capability of performer to use the reference in closed loop
|
- Perform same exact movement repeatedly to one accurate end point
- Increase Practice → Increase Learning
- Errors produced during learning → Increase strength of incorrect perceptual trace
|
| Schmidt's Schema Theory
|
Schmidt
|
1975
|
- Open Loop
- Schema - Abstract memory representation for events → RULE
- Generalized Motor Program - Rules that allow for the generation of novel movements
- Rapid, ballistic movements = recall memory withmotor programs and parameters to carry out movement without peripheral feedback
- Variability of Practice → Improve Motor Learning
|
- Optimal Learning → Task practiced under many different conditions
- Positive benefits for error production (learn from own mistakes)
- Schema has rules for all stored elements, not just correct elements
|
| Ecological Theory
|
Newell
|
1991
|
- Based on Systems & Ecological Motor Control Theories
- Motor Learning = Increases coordination between perception and action thru task & environmental constraints.
- Perceptual-motor workspace - Identifies movemets and perceptual cues most relevant to performance of task
- Optimal task-relevant mapping of perception & action → NO Rules!
|
- Patient learns to distinguish relevant perceptual cues important to action.
|
Theories Related to Stages of learning Motor Skills:
1) Fitts and posner Three Stage Model:(1967)
They suggest there are three main phases involved in skill learning
First stage:
Learner is focused on understanding the nature of task and developing strategies for the same.
Requires high degree of cognitive activity so referred as cognitive stage of learning.
Eg: first day of driving lesson of Mr Ben would require high degree of attention and consious thought
may make a lot of errors in gear shift and ABC control of manual car.
Second stage:
By this time person has selected best strategy for task and now begins to refine the skill
less variability in performance ,improvement occurs slowly
Referred as Associative stage of learning
Here,verbal/cognitive component not important as focus is on refining a particular pattern than focusing on alternative strategies.
eg: Mr Ben is learning to shuffle from second to third and then first gear as per the speed of vehicle while simultaneously applying ABC control.He is refining on his learned skills
Third stage:
Autonomous stage-there is automacity of skill and involves low degree of attention
Eg: Mr Ben can now enjoy a long drive with friends enjoying on the laughter,talks and the beautiful climate outside.
2)Systems Three Stage model:
Bernstein 1967
3 stages (novice, advanced, expert) theory of motor learning that accounts for reductions in body degrees of freedom seen in child development and new skill acquisition in general.
The novice stage involves the learner freezing degrees of freedom by
co-contracting agonists and antagonists to constrain a joint to simplify
the movement, as with the rigid bracing of the wrist when first
learning to use a hammer.
Degrees of freedom are progressively released
through the advanced and expert stages enabling movement at more joints
and more sophisticated muscle synergies across multiple joints until
smooth, coordinated movements are performed.
3)Gentile two stage Model
1972,1987
this theory of motor skill acquisition describes the goal of learner in each stage.
First stage :involves understanding the goal of the task,developing movement strategies appropriate to achieving goal and understanding environmental features critical to organization the movement.
-distinguishes relevant/regulatory features from non regulatory
Second is fixation/diversification stage,goal is to refine the movement.
References:
Ann Shumway Cook,Motor control 4th edition
Science Direct
Physiopedia
In the Next articles i will be discussing on skills and abilities and therapeutic application.
