1-5_Motor_Control_Theories_all motor control theories

motor control theories

1. Motor Control: Theories

2. Objectives
•Identify individual, task, and environmental
movement constraints
•Compare and contrast contemporary motor
control theories
•Compare and contrast neurologic
rehabilitation approaches with respect to
assumptions underlying normal and
abnormal movement control, recovery of
function, and clinical practices.

3. Reflection……
•What is a theory?
•What is the value of theory to clinical
practice?

4. HOW DOES MOVEMENT EMERGE?

5. Movement Emerges from the
Interaction between Task,
Individual, Environment

6. Environmental Constraints
on Movement
•Regulatory
–Essential elements that
determine the movement,
e.g. chair height
•Non-regulatory
–Feature that are not
essential but may affect
the performance, e.g.
background noise

7. Individual Constraints on
Movement
•Action
–“goal-directed”
movements
•Perception
–Sensory integration
•Cognition
–Mental functions
underlying the
establishment of a goal

8. Task Constraints on Movement
•The nature of tasks determine
the movement required.
•Classify tasks by
–Functional category, e.g.
gait, bed-mobility, transfer
–Discrete (definite ending) vs.
continuous (no end point),
e.g. grasping vs. walking
–Stable vs. mobility, e.g.
sitting vs. walking

9. Gentile’s Taxonomy for Task
Classification
M: manipulation, Variability: inter-trial variability
+ present, – absent

10. Gentile’s Taxonomy for Task
Classification
 
c
Body
Stability
Body
Transport
– M + M – M + M
Closed
predictable environment
– Variability    
+ Variability    
Open
unpredictable environment
– Variability       
+ Variability    
M: manipulation, Variability: inter-trial variability
+ present, – absent

11. MOTOR CONTROL THEORIES
– A TOUR THROUGH HISTORY

12. Discuss at your table group
1)What did the therapist do?
2)What did the patient do? How did the
patient perform the tasks?
http://www.youtube.c
om/watch?v=mCiBehv
_FOw&feature=relate
d
http://
www.youtube.co
m/watch?
v=r5o5S-9zGpE

13. Reflex Theory
Reflexes are the building blocks of complex
motor behaviors or movements

14. Reflex Theory
•Sir Charles Sherrington, the integrative
action of the nervous system (1906)
–Reflex chaining: complex movements are
a sequence of reflexes elicited together
•This is based on the observation that
monkeys were unable to their arm after
resection of one side of dorsal root ganglia.
 Therefore, sensory inputs must be
essential in initiating movements.

15. Limitations of Reflex Theory
•Unable to explain
–Spontaneous and voluntary movements
–Movement can occur without a sensory
stimulus
–Fast sequential movements, e.g. typing
–A single stimulus can trigger various
responses (reflexes can be modulated)
–Novel movements can be carried out.

16. Limitations of Reflex Theory
•Taub demonstrated that monkeys with
bilateral deafferentation were able to move
the arms. If with unilateral deafferentation,
the monkey relearned moving the affected
arm when the good arm was “constrained”
in a sling. His findings lead to the
constraint-induced movement therapy.
Stroke Rehabilitation: Constrained-Induced Movement Therapy
http://www.youtube.com/watch?v=MMTh2hWvB2g
Taub Therapy Clinic: Constrained-Induced Movement Therapy

17. Hierarchical Theory

18. Hierarchical Theory
•Higher centers are always in control of lower
centers
•Higher centers inhibit the reflexes controlled
by lower centers
•Reflexes controlled by lower centers are
present only when higher centers are damaged
•Neuromaturational theory of development
–The brain determines infant behavior!

19. Hierarchical Theory

20. Hierarchical Theory
•Based on the observation of motor
development in children and adults
–A child’s capacity to sit, stand, and walk
is related to the progressive emergence
and disappearance of reflexes
–Brain stem reflexes (associated with head
control) emerge before midbrain reflexes
(associated with trunk control)

21. Current Concepts Related to
Hierarchical Theory
•Each level of the
motor system can
act on other
levels
•Reflexes are one
of many
processes of
motor control

22. Clinical Implications of Hierarchical
Theory
“When the influence of higher centers is
temporarily or permanently interfered with,
normal reflexes become exaggerated and so
called pathological reflexes appear” …Brunnstrom,
1970
“The release of motor responses integrated at
lower levels from restraining, influences of
higher center, especially that of the cortex,
leads to abnormal postural reflex activity”…
Bobath, 1965

23. Limitations of Hierarchical Theory
•Environment and other non-CNS factors
can affect movement, e.g. Thelen’s
experiments showed that baby’s stepping
response re-emerges with body weight
support
•Normal adults exhibit lower level reflexes,
e.g. flexor withdrawal
Body Sense. Scientific America Frontier. (1:00-2:40, 5:10-7:30)
http://vsx.onstreammedia.com/vsx/pbssaf/search/PBSPlayer?
assetId=68932&ccstart=235620&pt=0&preview=undefined&en
tire=yes

24. •Concept of a central motor pattern or motor
program
–Many studies found that movement is
possible even in the absence of stimuli or
sensory input
–Sensory inputs are not required to
produce a movement but they are
important in adapting and modulating the
movement
Motor Programming Theories

25. General setup for studies of
locomotion in cats with spinal lesions
Rossignol, 2011

26. Central Pattern Generator (CPGs)
Rossignol, 2011
F flexor
motoneurons
E extensor
motoneurons
DC dorsal
columns
DRG dorsal
root ganglion

27. Evidence of a Motor Program:
Central Pattern Generator (CPGs)
•CPGs are spinal networks capable of
generating bilateral rhythmic movements,
such as swimming or walking, in the
absence of descending and sensory inputs
•CPGs are network of interneurons that
alternatively activate flexors and extensors
on one side, and coordinate with CPGs on
the other side

28. Motor Programming Theories
•Motor programs are
–Hardwired and stereotyped neural
connections such as central pattern
generators (CPGs)
–Abstract rules for generating movements
at the higher level
•Motor program can be activated by sensory
stimuli or by central processes

29. Writing
Motor Programming Theories

30. Limitations of Motor Programming
Theories
•Does not consider that the nervous system
must deal with both musculoskeletal and
environmental variables to produce
movements
–e.g. identical neural commands to elbow
flexors can produce different movements
depending on the initial position of the
arm and the force of gravity

31. Clinical Implications of
Motor Programming Theories
•Movement problems are caused by
abnormal CPGs or higher level motor
programs
•It is important to help patients relearn the
correct rules for action
•Focus on retraining movements that are
critical to a functional task, not just specific
muscles in isolation

32. Systems Theory: Bernstein’s
Degree of Freedom Problem
•How does the CNS select a solution
from an infinite number of
possibilities for a task?
•Solution
–Higher levels activate lower levels while
lower levels activate synergies, i.e. groups
of muscles that are constrained to act
together as a unit

33. Systems Theory: Bernstein’s
Degree of Freedom Problem
•Viewed body as a mechanical system,
involving the interaction between mass,
external force (e.g. gravity), internal force
•“Coordination of movement is the process
of mastering the redundant degrees of
freedom of the moving organism”
(Bernstein, 1967)

34. Systems Theory: Latash’s Principle
of Abundance
•Synergy is a task-specific covariation of
elemental variables with the purpose to stabilize
a performance variable, i.e. minimize errors of a
performance variable
–Reaching: joint rotation angle stabilize hand
position
–Grasping: individual finger force stabilize
total grasp force
–Standing stability: postural muscle activation
 stabilize COP

35. Systems Theory: Latash’s Principle
of Abundance
•A muscle belongs to more than one
synergy. Within a synergy, each muscle has
a unique weighting factor that specifies the
level of activation of that muscle within
that synergy.
•Synergies assure small variability of the
performance variable while allowing
relatively large variability of each elemental
variable

36. Postural perturbation study: each muscle
may be activated to a different degree by
each muscle synergy
Ting, 2005

37. Dynamic Systems Theory: Principle
of Self-Organization
•Movement emerges as a result of
interacting elements. No needs for specific
neural commands or motor programs.
•Variability of movement is normal. Optimal
amount of variability allows for flexible,
adaptive strategies to meet the
environmental demand

38. Dynamic Systems Theory: Principle
of Self-Organization
A new movement emerges when a control
parameter reaches a critical value

39. Limitation of Systems Theory
•Nervous system is fairly unimportant
•How do we apply mathematics and body
mechanics to clinical practice?

40. Clinical Implications of Systems
Theory
•Body is a mechanical system. Consider
musculoskeletal factors underlying a
patient’s movement problem
•Changes in movements may not necessarily
result from neural changes, e.g. faster vs.
slow gait, speed during sit to stand
•Encourage the patient to explore variable
movements

41. Ecological Theory: Gibson’s
Perception-Action Coupling
•Action is specific to the task goal and the
environment
•Perceptual information of the
environmental factors relevant to the task
goal is necessary to guide the action
•Limitations:
–↓ emphasis on nervous system

42. Clinical Implications of Ecological
Theory
•Individual is an active explorer of the
environment for learning
•Individual discovers multiple ways to solve
movement problems in environment
•Fundamental to the play-based therapy for
pediatric patients
Baby Sense. Scientific America Frontier. (1:00-2:40, 5:10-7:30)
http://vsx.onstreammedia.com/vsx/pbssaf/search/PBSPlayer?
assetId=68932&ccstart=235620&pt=0&preview=undefined&en
tire=yes

43. Discuss at your table group
What are the assumptions of movement
control underling each of these treatment
approaches?
http://
www.youtube.com/
watch?
v=mCiBehv_FOw&fea
ture=related
http://
www.youtube.c
om/watch?
v=r5o5S-9zGpE

44. NEUROLOGIC REHABILITATION
APPROACHES

45. Reflex
Contemporary

task-oriented
Neurotherapeutic

facilitation
Muscle

reeducation
Hierarchical Systems

Motor
control models
Neurologic
rehabilitation models

46. Muscle Reeducation
•Change function at
the level of muscle
•Vera Carter, a
practitioner
beginning her work
with muscle
treatment of polio
patients in Australia
in the early 1930’s
Kendall Historical Collection

47. Assumptions of Neurofacilitation
Approaches
•Abnormal movement is a direct result of
the neurologic lesion
•Inhibit abnormal movement patterns to
facilitate the normal movement patterns
will lead to the return of functional skills
•Repetition of normal movement patterns
will automatically transfer to functional
tasks

48. Reflex- and Hierarchical Based
Neurofacilitation Approaches
•Brunnstrom, Rood, Proprioceptive
neuromuscular facilitation (PNF), Bobath’s
neurodevelopmental treatment (NDT)
–Retraining motor control through
“techniques” to facilitate and/or inhibit
different movement patterns
–e.g. PNF UE D1 Flexion/Extension
http://davisplus.fadavis.com/kisner/Chap
ter06.cfm

49. Task-Oriented Approach (motor
control of motor learning approach)

50. Task-Oriented Approach
•Movement is organized around a behavioral goal
and is constrained by the environment
•Patients learn by actively attempting to solve the
movement problem rather than by repetitively
practicing normal patterns of movement.
–e.g. RIC constraint-induced movement therapy
camp http://www.youtube.com/watch?
v=NhLsh1SW4Ak

51. Moving forward
“….currently available evidence of dose–
response relationships in motor learning,
time-dependency of neuronal and functional
recovery, and task specificity of treatment
effects….…the lack of evidence as well as
major changes over time in our
understanding of underlying mechanisms
about stroke recovery, which do not concur
with the obsolete and constantly changing
assumptions used to explain the Bobath
Concept…”Kollen, 2009