7112195 Motor Control Theories

Motor Control

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Motor Control

MOVEM

ENT

S &

SKILLS

Motor Control

Movement

Movement is a critical aspect of life.Life would not be possible without the

capacity to move. WHAT IS MOVEMENT ??

Motor Control

Types of Movements

Inherited or Self-Differentiated

Genetically definedEg: One’s control over their limbs

Movements

Learned

Not inherited and mastering them requires long periods and experience.Eg: Operating a typewriter

Motor Control

SKILLS

Learned Movements are termed as Skill Movements.

Guthrie: “Skill consists in the ability to bring about some end result with maximum certainty and minimum outlay of energy, or time and energy.”

Classification of Skill:– Depending on size of musculature required– Depending on specificity of where actions begin & end– Depending on stability of the environment context

Motor Control

Fine Motor Skills

Size of primary Musculature Required

Gross Motor SkillsPrimary Musculature required = Large & Small

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1

Continuous Motor Skills

2

Serial Motor Skills

Specificity of where actions begin & end

3

Discrete Motor Skills

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Closed Motor SkillOpen Motor Skill

Stability of Environment ContextMotor Control

Stability

Factors Constraining Movement

Mobility

Man

ipul

atio

n

T

I E

Regulatory

NonRegulatory

Cognition

Perception A

ctio

n

Motor Control

ELOVUTIO

N

OF

MOTOR

CONTROL

Motor Control

Evolution of Motor Control

Emerged from two isolated bodies of knowledge:

• Branch of Neurophysiology (neural processes associated with Movements but not movements itself)

• Branch of Psychology & related fields (Concerned with high level skills with little reference to neurological mechanisms)

Motor Control


Around 1820: Bessel (Astronomer)• Process underlying differences among his

colleagues in recording the transit times of the movements of stars.

1882: Bowditch & Southard• Studying hand movements in localizing targets

1892: Fullerton & Cattell• Examined force reproducibility

1899: Woodworth• Fundamental principles of rapid arm & hand

movements

Motor Control


During middle and late 1800s:• Memory for movements• Speed-Accuracy Trade-Offs• Phase Transitions in Bimanual Movements

1914: Thorndike• Processes underlying learning skills & other

behaviors• Law of Effect (Responses followed by reward tend

to repeat)• Differences among individuals over practice

Motor Control

Evolution of Motor Control 1935 - 1940: Bayley, McGraw & others

• Started studying the area now known as Motor Development

1892 – 1895: Blix and Weber• Identified Characteristics & Contractile properties

of muscle tissue

1870s: Jackson• Investigations of neural control of movement

These contributions lead to evolution of Physiological or Neural bases of Movement

Motor Control


1870: Fritsch & Hitzig

• Brain is electrically excitable and lead to development of electrophysiological techniques

1888: Ferrier• Investigated responses in the cortex to artificial

movements

1887, 1890: Beevor & Horsely• Sensory & Motor areas of Brain

Motor Control

Evolution of Motor Control Contribution by Sherrington

• Studied & classified major responses to stimuli presented to extremities

– Voluntary movements resulted from these fundamental reflexes

• Reciprocal Innervation: When flexors of a joint are activated, the extensors tend to be automatically deactivated, and vice versa.

– Golgi Tendon Organ: Signal changes in muscle tension– Muscle Spindle: Perception of muscle length & hence

joint position

• Proprioception: Sense of body position & orientation thought to be signaled by various muscle & joint receptors together with receptors located in the inner ear.

Motor Control

Evolution of Motor Control 1943: Hull

• Theories of Learning• How fatigue and recovery processes combined to

determine learning of motor skills

1948: Craik• Brain works as a computer (Information is

received, processed and then output to environment in the form of actions of limbs)

• Central Tendency: Humans responds in discrete bursts rather than continuous

1949: Wiener• Information Processing Theory

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1954: Fitts• Fitts’s Law: Model of human movement which

predicts the time required to rapidly move to a target area, as a function of the distance to the target and the size of the target

1970s:• North American Society for the Psychology of

Sport & Physical Activity (NASPSPA)• Canadian Society for Psycho-Motor Learning &

Sport Psychology

Motor Control

Motor Control Today

1967: Neisser• Stimulus-Response Theory:

1970 – 1989: Pew, Schmidt• Transition from Task Orientation to Process

Orientation– Task orientation focuses primarily on the effects of

variables on the performance of certain motor task– Process orientation focuses on the underlying mental or

neural events that support or produce movements

Motor Control

Motor Control Today 1966: Adams & Dijkstra, Posner & Konick

• Short-term Memory which explained processes underlying memory loss in simple movements over short period of time.

1971: Adams• Feedback-based theory for motor learning

1974: Pew• Movement Schema: Abstract hypothetical

structures responsible for movement control & evaluation

1975: Schmidt• Presented the Schema Theory for learning simple

motor skills

Motor Control

Motor Control Today After 1970s:

• Merger between Neural Control & Motor Behavior• Neural Mechanisms studies by experiments on

animals• Association between movement behaviors and

neurological processes which provided more complete understanding of how movements where controlled

• Development of advanced techniques– Electrophysiological recordings– Cinematographic & 3-D analysis– Measurements of kinematics of movement– Advanced methods examining involvement of brain

structures in learning

Motor Control

Motor Control Today

Understanding of Degrees of Freedom Problem

• How system with many independent parts could be controlled without need for an executive decision marker

• Laws and principles for coordination and degrees of freedom

1995: Kelso• Dynamic Pattern Perspective suggested that

coordinated movements evolves over time as a function of interaction between body parts, and between the body parts and physical world.

Motor Control

Motor Control TodayMotor Control

Motor Control TodayMotor Control

INPUTS FROM DR. CAURAUGHINPUTS FROM

DR. CAURAUGH

CURRENT INSIGHTSCURRENT INSIGHTS

THEORIES

OF

MOTOR

CONTROL

Motor Control

Theories of Motor Control

Theory: Is a set of concepts, propositions, or definitions that are interrelated in some ways.

They are used to specify relationship among different variables so that we can obtain a systematic view of specific types of phenomena.

Motor Control

Applications of Motor Control TheoriesMotor Control

Motor Control Theories

Most of the Motor Control Theories incorporate two basic systems of control.

Open-Loop Control System Closed- Loop Control System

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Open-Loop Motor Control SystemMotor Control

INPUT

INPUT

SENSORY FEEDBACK

Movement Commands

Open-Loop Motor Control System A set of muscle commands that are structured

before a movement begins that specifies a sequence to be carried out that is uninfluenced by peripheral feedback.

Advantages: The production of very fast movements in absence of

feedback Feedback does not have to be processed during

movements

Disadvantages: Not effective when environmental situations are

constantly changing Not good for very precise movements

Motor Control

Closed-Loop Motor Control SystemMotor Control

INPUT

INPUT

SENSORY FEEDBACK

Movement Commands

Updated Movement Commands

Closed-Loop Motor Control System

Feedback can be used not only to plan and initiate movements but also to adjust progress in an ongoing movement.

Advantages: Allows for a great deal of movement flexibility Can be used to produce very accurate movements

Disadvantages: Execution of corrections tends to be attention

demanding Very time demanding so not applicable to open,

reactive sport situations.

Motor Control

Application of Open & Closed Loop Systems

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Motor Control Theories

Reflex Theory Ecological Theory Hierarchical Theory Motor Programming Theories System Theory Dynamical Action Theory

Motor Control

Reflex Theory

Charles Sherrington (Neurophysiologist) Reflexes are the building blocks

(fundamental units) of Motor Control. Reflexes worked together or in sequence

to achieve a common purpose. Physical events occurring in the

environment served as the STIMULUS for action, triggering chain of individual reflex circuits that were responsible for producing a movement RESPONSE.

Motor Control

Reflex Theory Reflex requires three basic structures:

Receptor• Sensory receptors in skin, muscles & joints and other

sensory systems

Conducting nervous pathway Afferent Nervous Pathway

• Carries impulses from receptors towards the CNS

Efferent Nervous Pathway• Carries impulses away from CNS to effector organs

Effector Organs Muscles

Motor Control

Reflex TheoryMotor Control

Reflex Theory

Sherrington concluded that with the whole nervous system intact, the reaction of the various parts of that system, the simple reflexes, are combined into greater actions that constitute the behavior of the individual as a whole.

Reflex Chaining:• A stimulus leads to a response, which becomes the

stimulus for the next response, which becomes the stimulus for the next response.

Motor Control

Stimulus Response Response

Clinical Implications of Reflex Theory

If chained or compounded reflexes are the basis for the functional movement, clinical strategies designed to test reflexes should allow therapists to predict function.

Patient’s movement behaviors would be interpreted in terms of presence or absence of controlling reflexes.

Retraining motor control for functional skills would focus on enhancing or reducing the effect of various reflexes during motor tasks.

Motor Control

Limitations of Reflex Theory

Reflex must be activated by an outside agent, theory cannot explain voluntary or spontaneous movement.

Cannot explain movement that occurs in the absence of a sensory stimulus.

Cannot explain movements that occur too rapidly. Fails to explain that a single stimulus can result in

varying responses depending on context and descending commands.

Does not explain the ability to produce novel movements.

Motor Control

Ecological Theory

James Gibson (1966 - Psychologist) How motor systems allow us to interact

most effectively with the environment to perform goal-directed behavior

Motor Control evolved so that animals could cope with the environment around them, moving in it effectively to find food, run away from predators, build shelter, and even play.

Motor Control

Ecological TheoryMotor Control

INDIVIDUAL

ENVIRONMENT

EN

VIR

ON

ME

NT

EN

VIR

ON

ME

NT

ENVIRONMENT

Ecological Theory

Actions require perceptual information that is specific to desired goal-directed action performed within a specific environment.

The organization of action is specific to the task and the environment in which the task is being performed.

Motor Control

Ecological TheoryMotor Control

Sensations

Ecological Theory

Perception focuses on detecting information in the environment that will support the actions necessary to achieve the goal.

From ecological perspective, it is important to determine how an organism detects information in the environment that is relevant to action, what form this information takes, and how this information is used to modify and control movement.

Motor Control

Clinical Implications Ecological Theory

Describes individual as an active explorer of the environment which allows individual to develop multiple ways to accomplish a task.

This may help patients to explore more and find different options to execute particular task and then analyze the most suitable and efficient way.

Motor Control

Limitations of Ecological Theory

Inability of the theory to explain the organization and function of the nervous system, which led to this interaction between the individual and the environment.

Motor Control

Hierarchical Theory

Hughlings Jackson (Physician)

• Organizational control which is TOP DOWN

• The Nervous System is controlled so that the higher centers control and influence lower centers on a strictly hierarchical basis.

Motor Control

Hierarchical Theory

Rudolf Magnus• Reflexes are part of hierarchy of motor control, in

which higher centers inhibit these lower reflex centers.

Georg Schaltenbrand• Described development of mobility in terms of

appearance and disappearance of a progression of hierarchically organized reflexes.

• Pathology of brain may result in persistence of primitive lower level reflexes.

• Understanding of reflexes would allow, determination of neural age of a child or a patient with motor control dysfunction.

Motor Control

Hierarchical Theory

Stephan Weisz Hierarchically organized reflex reactions

(basis for equilibrium in humans) Explained the relationship between the

maturation of equilibrium reflexes and the child’s ability to sit, stand and walk.

Motor Control

Hierarchical Theory

Arnold Gesell & Myrtle McGraw Neuromaturational Theory

Attributes normal motor development to increasing corticalization of the CNS

Assumes that CNS maturation is the primary agent for the change in development.

Motor Control

Hierarchical Theory

Example: Reaching The component parts of the stored movement

program in the brain are activated; These exert either a facilitatory or inhibitory

influence on spinal neurons & interneuron's via corticospinal pathways

Neuromuscular activity is initiated to complete the task

Once the movement has been learnt it can be performed without the need for peripheral feedback.

Motor Control

Clinical Implication of Hierarchical Theory

Reflex assessment profiles are used to estimate the level of neural maturation and predict functional ability.

• When influence of higher centres is temporarily or permanently interfered with, normal reflexes become exaggerated and so called pathological reflexes appear. (Brunnstrom)

• Release of motor responses integrated at lower levels from restraining influences of higher centres, especially that of the cortex, leads to abnormal postural reflex activity. (Bobath)

Motor Control

Limitation of Hierarchical Theory

Cannot explain dominance of reflex behavior in certain situations in adults. Eg: Stepping on pins results in immediate

withdrawal of the leg. Reflex within the lowest level of the hierarchy

dominating motor function. (BOTTOM UP CONTROL)

All low-level behaviors are primitive, immature and non-adaptive.

Higher level (cortical) behaviors are mature, adaptive and appropriate.

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Motor Programming Theories

Wilson, Grillner, Taub Can have patterned motor response with

or without sensory stimulus Explanation based on Physiology of

Actions rather than Physiology of Reactions

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Motor Programming TheoriesMotor Control


Experimental Evidences in support for these theories Grasshopper or Locust experiment

• Wing beat in flight depended on rhythmic pattern generator

• Absence of sensory nerves – nervous system by itself generated the movements but were slowed

• Hence, sensory inputs are not essential in driving the movements but has important function in modulating the actions.

Motor Control


Experimental Evidences in support for these theories Locomotion in cats experiment

• Without sensory inputs or descending patterns from brain also rhythmic locomotor actions can be produced by the spinal neural networks

• Reflexes do not drive the action, but the central pattern generators (spinally mediated motor programs) by themselves can generate complex movements.

Motor Control


Motor Program – two meanings Central pattern generator (CPG)- specific

neural circuit in spinal cord– Neural networks that can endogenously (i.e. without

rhythmic sensory or central input) produce rhythmic patterned outputs or as neural circuits that generate periodic motor commands for rhythmic movements such as locomotion

Motor program – stored rules for generating movements so that we can perform the tasks with a variety of effector systems; prestructured set of motor commands

Motor Control

Motor Programming Theories Central pattern generator (CPG)

• To be classified as a rhythmic generator, a CPG requires: – Two or more processes that interact such that each process sequentially

increases and decreases– As a result of this interaction, the system repeatedly returns to its starting

condition.

• Three roles of modulation have been found for CPG circuits:– Modulation in CPG as Part of Normal Activity – Modulation Changes the Functional Configuration of CPGs to Produce

Different Motor Outputs

– Modulation Alters CPG Neuron Complement by Switching Neurons Between Networks and Fusing Formerly Separate Networks into Larger

Entities • Functions in vertebrate animals:

– Movement– Breathing– Rhythm Generation and other Oscillatory Functions

Motor Control


Central Pattern Generator (CPG) Grillner, 1975 - inherited system for patterned

movements – e.g. locomotion, chewing– Initiated by a triggering stimulus – Centrally organized – No need for sensory input – Primarily dealing with alternating repetitive movements

Central pattern generator (CPG) vs. motor program:

– CPG = genetically predetermined activities – Motor program = learned activities

Motor Control

Clinical Implications of Motor Programming Theories

If higher levels of motor programming are not affected, can use alternate effectors.

If cortex is damaged, you have to re-teach the rules. Intervention should focus on retraining

movements important to a functional task, not just on reeducating specific muscles in isolation

Motor Control

Limitations of Motor Programming Theories

CPG- expansion of knowledge of flexibility of the nervous system in creating movements, does not explain sensory input importance

Motor program concept does not take into account musculoskeletal system and environmental variables.

Motor Control

Systems Theory

Nicolai Bernstein (Russian Scientist) Output of Nervous System as filtered

through a mechanical system, the body.• Taken into account different factors like, mass,

forces such as gravity and internal forces including both inertial & Movement-dependent forces.

Same central commands could result in quite different movements because of the interplay between external forces and variations in the initial conditions.

Motor Control

Systems Theory

Control of integrated movement is probably distributed throughout many interacting systems working cooperatively to achieve movement. (Distributed Model of Motor Control)

Coordination of movement is a process of mastering the redundant degrees of freedom.

Motor Control

Systems TheoryMotor Control

Clinical Implications of Systems Theory

Need to assess CNS deficits as well as

Musculoskeletal System Examination and intervention must focus

not only on the impairments within individual systems contributing to motor control, but the effect of interacting impairments among multiple systems.

Motor Control

Limitations of Systems Theory

Systems theory does not focus on the interaction of the organism with the environment.

Difficult to relate theoretical components to neuro-anatomy.

Model is abstract.

Motor Control

Motor Control

Information Processing Theory

Information processing theorists proposed that like the computer, the human mind is a system that processes information through the application of logical rules and strategies.

Like the computer, the mind has a limited capacity for the amount and nature of the information it can process.

Motor Control


Computer can be made into a better information processor by changes

• in its hardware (e.g., circuit boards and microchips) • its software (programming)

Humans become more sophisticated thinkers through changes

• in their brains and sensory systems (hardware) • in the rules and strategies (software) that they

learn.

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Information Processing TheoryMotor Control



Sensory Register Capacity

• Very large

Duration• 0.5 to 3 seconds

Contents• Information perceived by the sensory receptors

(encoded as perceived)

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Sensory Register & its Control Processes Recognition

• Noting key features of a stimulus and relating them to already stored information

Attention• Selective focusing on a portion of the information

currently stored in the sensory register

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Short Term Memory Capacity

• 7 +/- 2 chunks of information

Duration• 20 to 30 seconds

Contents• What you are currently thinking about (information

from the sensory register and information from long term memory)

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Short Term Memory & its Control Processes Rehearsal

• Maintenance rehearsal – Repeating information over and over again; no effect on

long-term memory storage

• Elaborative rehearsal– Relating new information to knowledge already stored in

long-term memory

Motor Control



Long Term Memory Capacity

• Unlimited

Duration• Permanent, long-term

Contents• Schemata

– In general is a specific, well-documented, and consistent plan.

– In psychology and cognitive science, is a mental structure that represents some aspect of the world.

– People use schemata to organize current knowledge and provide a framework for future understanding.

Motor Control




SENSORY

REGISTERS

SENSORY

REGISTERS

Info

rmati

on /

Data

eyes, ears, nose, mouth, skin


SENSORY

REGISTERS

SENSORY

REGISTERS

Short-term store

Infinite data are briefly maintained (0.5 – 3.0

seconds) for preliminary analysis.

some info is selected for short term

memory

Info

rmati

on /

Data


SENSORY

REGISTERS

SENSORY

REGISTERS

Short-term store



Short-term (working) memory

(A limited amount of data is maintained

for approximately 20 seconds.

some info is transferred to

working memory

Info

rmati

on /

Data


SENSORY

REGISTERS

SENSORY

REGISTERS

Short-term store






Long-Term memory.

Transformed or coded data

become part of the knowledge

system.

even less passes on to long term memory to storage

Info

rmati

on /

Data


Data lost from the system Data lost from the system

SENSORY

REGISTERS

SENSORY

REGISTERS

Short-term store






Long-Term memory.



system.

some info is lost

Info

rmati

on /

Data


EXECUTIVE CONTROL PROCESSESEXECUTIVE CONTROL PROCESSES

Data lost from the system Data lost from the system

SENSORY

REGISTERS

SENSORY

REGISTERS

Short-term store






Long-Term memory.



system.

metacognitive processes control the whole process

Info

rmati

on /

Data


QUESTIONS!!!Motor Control

Motor Control

7112195 Motor Control Theories

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