Lecture Three: Theories of Motor Control

Question 1

Prominent Theories of Motor Control

Answer 1

• Reflex/Hierarchical Theories
• Motor Programming Theories
• Systems/Dynamic Systems Theory
• Ecological Theory

Question 2

Reflex/Hierarchical Theories Purpose

Answer 2

Provide an attempt to reduce complex human behavior to combinations of reflex behavior
It was originally two separate theories: Reflex Theory and Hierarchical Theory

Question 3

Reflex Theory

Answer 3

• Sir Charles Sherrington: Reflexes= building blocks of complex behavior
  Stimulus —> Response
  -Complex motor behavior results from “ chaining” of simple reflexes into combines patterns of activity
  Stimulus —> Response(stimulus) —> Response(Stimulus)

Question 4

Hierarchical Theory

Answer 4

• Hughling Jackson: Nervous system is organized as hierarchy
• Top—> Down Control of the CNS
• The higher levels control the lower levels

Question 5

Historical Assumption of the Reflex/Hierarchical Theory

Answer 5

• Motor control emerges from reflexes that exist within hierarchically organized levels of the CNS
• Higher centers dominate the lower centers
  ~ If the higher centers are damaged, lower behaviors ( abnormal, reflex-based movements) will take over function and will interfere with normal movement

Question 6

Limitation with Reflex/Hierarchical Theory

Answer 6

Movement can occur without an outside stimulus and one stimulus can result in various response depending on the context ( movement is not stereotyped)
-Doesn’t explain fast movements
Some reflexes are not inhibits normally- lower systems dominated higher

Question 7

Reflex-based Neurofacilitation Intervention Approaches

Answer 7

Late 1950, early 1960s
Interventions for neurological impairments
Historically: Techniques designed to facilitate” normal” movement patterns or inhibit abnormal movement patterns( reflexes)
Assumed that functional skills will automatically return when abnormal movement patterns are inhibited, and that facilitation of “normal” movement will transfer to functional task.
Currently more emphasis on function and motor learning

Question 8

Motor Program Definition

Answer 8

• Pre-developed patterns of muscle activity
• Programs activated by sensory stimuli or by central processes ( with or without sensory stimuli, not just reactive as with reflex theory)

Question 9

Motor Programming Theories: Central Pattern Generators

Answer 9

• Spinal circuit capable of producing a rhythmic functional behavior, such as walking and breathing
• Distributes throughout each segment of the spinal cord
• Evidence for CPG : locomotion in cats

Question 10

Ecological Theory

Answer 10

Gibson 1966

• Movement is specific to task and environment
• Perception/action system
• Need to examine how the individual perceives info in environment related to task and uses this info to modify and control movement

Question 11

Ecological Theory

Answer 11

Sensation vs Perception ( of the environment)

Perception/Action Coupling

Question 12

Ecological Theory

Answer 12

• Individual is an active explorer of environment
• Active exploration allows adaptability and variability of task performance
• “What we are doing now provides feedback for deciding what to do next”- K Adolph
• Learn how to adopt their movement
  Ex: Babies walking on sand for the first time, have to make adjustments

Question 13

Clinical Application of Ecological Theory

Answer 13

Interventions should emphasize performing a task in various ways
Encourage exploration of various environments so patient can learn to perceive critical features for adapting movement

Question 14

Systems theory

Answer 14

Bernstein( 1967)

• Movement is influenced by external forces ( gravity, environment & task) and internal forces( neurological, musculoskeletal factors) acting on the body
• Control of movements distributes cooperatively throughout interacting subsystems( neurological, musculoskeletal, etc)

Question 15

System Theory : Body as Mechanical Systems

Answer 15

Skilled movement takes advantages of the muscular and non muscular forces acting on the body

• Body is a mechanical system with numerous joint & muscles that need to be controlled for any task
• Role CNS is to control, organize, and coordinate these degrees of freedom and effects of gravity/external forces in movement synergies
• Synergies are muscle linage( locomotor, postural, respiratory)

Question 16

Evolution of Systems Theory: Dynamic Systems Theory

Answer 16

Self Organization

• Body systems come together so that subsystems behave collectively in an ordered way for way
• Behavior is not specified in advance but is assembled on the spot by interaction of the organism, task and environment

Question 17

Role of Variability : Dynamic Systems Theory

Answer 17

Inherent movement variability:

• Necessary condition to optimize function and skill
• Allows for flexibility and adaptability in order to adjust to changes in task and environment
• Too little variability= to little movement
• To much variability = to much movement

Question 18

Dynamic Systems Theory: Variability

Answer 18

Small amount of variability in movement pattern = attractor state ( preferred pattern of movement for efficiency)

Question 19

Attractor Well

Answer 19

• Degree of flexibility to change the preferred pattern of movement
• Deeper well = more stable movement pattern ( harder to change)

Question 20

Clinical Relevance: Dynamic System Theory

Answer 20

Examination and interventions for all patients need to consider impairments in all systems as possibly impacting motor control

• Consider task traits and environment features
• Practice variability in movements for task performance
• High stability of movement patterns may be difficult to retrain and instead need compensation