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Motor control

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MOTOR CONTROL - THEORIES

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Motor control

  1. 1. LEARNING OBJECTIVES STUDENTS WILL BE ABLE TO – DEFINE MOTOR CONTROL, AND DISCUSS ITS RELEVANCE TO THE CLINICAL T/T OF PATIENTS WITH MOVEMENT PATHOLOGY. DISCUSS HOW FACTORS RELATED TO THE INDIVIDUAL, THE TASK, AND THE ENVIRONMENT AFFECT THE ORGANIZATION AND CONTROL OF MOVEMENT. ENUMERATE THE THEORIES OF MOTOR CONTROL AND ITS VALUE TO CLINICAL PRACTICE COMPARE AND CONTRAST THE NEUROFACILITATION APPROACHES TO THE TASK ORIENTED APPROACH.
  2. 2. INTRODUCTION •DEFINITION: MOTOR CONTROL IS DEFINED AS THE ABILITY TO REGULATE OR DIRECT THE MECHANISMS ESSENTIAL TO MOVEMENT. •THE FIELD OF MOTOR CONTROL IS DIRECTED AT:  STUDYING THE NATURE OF MOVEMENT HOW MOVEMENT IS CONTROLLED.
  3. 3. WHY SHOULD THERAPIST STUDY MOTOR CONTROL? •DIRECTED AT CHANGING MOVEMENT OR INCREASING THE CAPACITY TO MOVE. •STRATEGIES - DESIGNED TO IMPROVE THE QUALITY AND QUANTITY OF POSTURE AND MOVEMENTS ESSENTIAL TO FUNCTION.
  4. 4. NATURE OF MOVEMENT •MOVEMENT EMERGES FROM INTERACTION OF THREE FACTORS: “THE INDIVIDUAL, THE TASK AND THE ENVIRONMENT”. M TASK ENVIRONMENTINDIVIDUAL
  5. 5. FACTORS WITHIN THE INDIVIDUAL THAT CONSTRAINT MOVEMENT
  6. 6. TASK CONSTRAINTS ON MOVEMENT MOVEMENT STABILITY MOBILTY MANIPULATION
  7. 7. • BUT WHAT TASKS SHOULD BE TAUGHT? • IN WHAT ORDER? • WHAT TIME? • THUS UNDERSTANDING OF TASK ATTRIBUTES CAN PROVIDE A FRAMEWORK FOR STRUCTURING TASKS. • TASKS CAN BE SEQUENCED FROM LEAST TO MOST DIFFICULT BASED ON THEIR RELATIONSHIP TO A SHARED ATTRIBUTE.. • CONCEPT OF GROUPING AND CLASSIFYING TASKS  FUNCTIONAL TASK GROUPINGS.  ACCORDING TO CRITICAL ATTRIBUTES. MOBILITY TASKS MANIPULATION COMPONENT MOVEMENT VARIABILITY
  8. 8. FUNCTIONAL TASK GROUPING Functional categories
  9. 9. FUNCTIONAL TASK GROUPING
  10. 10. MANIPULATION COMPONENT Standing and lifting a heavy load Standing and lifting a light load standing
  11. 11. MOVEMENT VARIABILITY STABILITY QUASIMOBILE MOBILITY Closed predictable environment sit/stand/non- moving surface Sit to stand/ kitchen chair/arms Walk/non-moving surface Open unpredictable environment Stand/rocker board Sit to stand/rocking chair Walk on uneven or moving surface
  12. 12. ENVIRONMENTAL CONSTRAINTS ON MOVEMENT MOVEMENT REGULATORY NON REGULATORY
  13. 13. THE CONTROL OF MOVEMENT: THEORIES OF MOTOR CONTROL •A THEORY OF MOTOR CONTROL IS A GROUP OF IDEAS ABOUT THE CONTROL OF MOVEMENT. •A THEORY IS A SET OF INTERCONNECTED STATEMENT THAT DESCRIBES UNOBSERVABLE STRUCTURES OR PROCESSES AND RELATE THEM TO EACH OTHER AND TO OBSERVABLE EVENTS.
  14. 14. VALUE OF THEORY TO PRACTICE THEORY PROVIDES - FRAME WORK FOR INTERPRETING BEHAVIOUR GUIDE FOR CLINICAL ACTION NEW IDEAS: DYNAMIC & EVOLVING WORKING HYPOTHESIS FOR EXAMINATION & INTERVENTION
  15. 15. THEORIES REFLEX HIERACHICAL MOTOR PROGRAMMING SYSTEMS DYNAMIC ACTION ECOLOGICAL
  16. 16. REFLEX THEORY • ESTABLISHED BY CHARLES SHERRINGTON, A NEUROPHYSIOLOGIST. • HIS RESEARCH ON SENSORY RECEPTORS LEAD TO VIEW THAT MOVEMENT WAS RESULT OF STIMULUS-RESPONSE SEQUENCE OF EVENTS OR REFLEX BASED • STIMULUS RESPONSE • SENSATION ASSUMED A PRIMARY ROLE IN INITIATION AND PRODUCTION OF MOVEMENT. • HE BELIEVED ,REFLEXES WERE THE BUILDING BLOCKS OF COMPLEX BEHAVIOR.
  17. 17. LIMITATIONS • THE REFLEX CANNOT BE CONSIDERED THE BASIC UNIT OF BEHAVIOUR IF BOTH SPONTANEOUS AND VOLUNTARY MOVEMENTS ARE RECOGNISED AS ACCEPTABLE CLASSES OF BEHAVIOUR AS IT MUST BE ACTIVATED BY AN OUTSIDE AGENT. • DOES NOT ADEQUATELY EXPLAIN AND PREDICT MOVEMENT THAT OCCURS IN THE ABSENCE OF SENSORY STIMULUS. E.G ANIMALS MOVE – ABSENCE OF SENSORY STIMULUS • DOES NOT ADEQUATELY EXPLAIN FAST MOVEMENTS.SEQUENCE OF MOVEMENTS THAT OCCUR TOO RAPIDLY TO ALLOW SENSORY FEEDBACK FROM PRECEDING MOVEMENT TO TRIGGER THE NEXT E.G TYPING • FAILS TO EXPLAIN THE FACT THAT A SINGLE STIMULUS CAN RESULT IN VARYING RESPONSES DEPENDING ON CONTEXT AND DESCENDING COMMANDS. E.G OVERRIDE REFLEXES TO ACHIVE GOAL. • DOES NOT EXPLAIN THE ABILITY TO PRODUCE NOVEL MOVEMENTS. E. G VIOLINIST
  18. 18. CLINICAL IMPLICATIONS •CLINICAL STRATEGIES DESIGNED TO TEST REFLEXES SHOULD ALLOW THERAPISTS TO PREDICT FUNCTION. •PATIENT’S MOVEMENT BEHAVIORS WOULD BE INTERPRETED IN TERMS OF THE 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. E.G FACILITATION / INHIBITION.
  19. 19. HIERARCHICAL THEORY •MANY RESEARCHERS HAVE CONTRIBUTED TO THE VIEW THAT NERVOUS SYSTEM IS ORGANIZED AS A HIERARCHY. •AMONG THEM, HUGHLINGS JACKSON, AN ENGLISH PHYSICIAN ARGUED THAT THE BRAIN HAS HIGHER, MIDDLE AND LOWER LEVELS OF CONTROL, EQUATED WITH HIGHER ASSOCIATION AREAS, THE MOTOR CORTEX AND THE SPINAL LEVELS OF MOTOR FUNCTION. •THE HIERARCHICAL CONTROL MODEL IS CHARACTERIZED BY A TOP-DOWN STRUCTURE, IN WHICH HIGHER CENTERS ARE ALWAYS IN CHARGE OF LOWER CENTERS.
  20. 20. CURRENT CONCEPTS RELATED TO HIERARCHICAL CONTROL • THE CONCEPT OF STRICT HIERARCHY HAS BEEN MODIFIED. • WITHIN THIS MODIFICATION, THE ASSOCIATION CORTEX OPERATES AS THE HIGHEST LEVEL(ELABORATING PERCEPTION AND PLANNING STRATEGIES) • WHILE SENSORY-MOTOR CORTEX IN ASSOCIATION WITH THE PORTIONS OF THE BASAL GANGLIA, BRAIN STEM AND CEREBELLUM FUNCTION AS THE MIDDLE LEVEL(CONVERTING STRATEGIES INTO MOTOR PROGRAMS AND COMMANDS). THE SPINAL CORD FUNCTIONS AT THE LOWEST LEVEL, TRANSLATING COMMANDS INTO MUSCLE ACTIONS RESULTING IN THE EXECUTION OF MOVEMENT. • MODERN HIERARCHICAL THEORY PROPOSES THAT THE THREE LEVELS DO NOT OPERATE IN A RIGID, TOP-DOWN ORDER BUT RATHER AS A FLEXIBLE SYSTEM IN WHICH EACH LEVEL CAN EXERT CONTROL ON THE OTHERS. • SHIFTS IN CONTROL ARE DEPENDENT ON THE DEMANDS AND COMPLEXITY OF THE TASK WITH THE HIGHER CENTERS ALWAYS ASSUMING CONTROL.
  21. 21. LIMITATIONS • CANNOT EXPLAIN THE DOMINANCE OF REFLEX BEHAVIOUR IN CERTAIN SITUATIONS IN NORMAL ADULTS. E.G.. STEPPING ON A PIN RESULTS IN AN IMMEDIATE WITHDRAWAL OF LEG. THIS IS AN EXAMPLE OF A REFLEX WITHIN THE LOWEST LEVEL OF HIERARCHY DOMINATING MOTOR FUNCTION. • LIMITATION OF HIERARCHICAL THEORY REFLEX WITHIN THE LOWEST LEVEL OF THE HIERARCHY DOMINATING MOTOR FUNCTION. (BOTTOM UP CONTROL) • ALL LOW-LEVEL BEHAVIOURS ARE PRIMITIVE, IMMATURE AND NON-ADAPTIVE, WHILE ALL HIGHER LEVEL (CORTICAL) BEHAVIOURS ARE MATURE, ADAPTIVE AND APPROPRIATE.
  22. 22. CLINICAL IMPLICATIONS • SIGNE BRUNNSTROM, USED A REFLEX HIERARCHICAL THEORY TO DESCRIBE DISORDERED MOVEMENT FOLLOWING A MOTOR CORTEX LESION. • SHE STATED “WHEN THE INFLUENCE OF HIGHER CENTERS IS TEMPORARILY OR PERMANENTLY INTERFERED WITH THE NORMAL REFLEXES BECOME EXAGGERATED AND SO CALLED PATHOLOGICAL REFLEXES APPEAR”. • “THE RELEASE OF MOTOR RESPONSES INTEGRATED AT LOWER LEVELS FROM RESTRAINING INFLUENCES OF HIGHER CENTERS, ESPECIALLY THAT OF THE CORTEX LEADS TO ABNORMAL POSTURAL REFLEX ACTIVITY”(BOBATH,1965;MAYSTON,1922).
  23. 23. MOTOR PROGRAMMING THEORIES • REFLEX THEORIES HAVE BEEN USEFUL IN EXPLAINING CERTAIN STEREOTYPED PATTERNS OF MOVEMENT. • ONE CAN REMOVE THE STIMULUS, OR THE AFFERENT INPUT AND STILL HAVE A PATTERNED MOTOR RESPONSE.(VAN SANT,1987). • E.G GRASSHOPPER – FLIGHT DEPENDED ON RHYTHMIC PATTERN GENERATOR. EVEN WHEN SENSORY NERVES WERE CUT, THE NERVOUS SYSTEM COULD GENERATE THE OUTPUT WITH NO SENSORY INPUT – BUT WING BEAT WAS SLOW
  24. 24. MOTOR PROGRAMMING THEORIES • CONCEPT OF CENTRAL MOTOR PATTERN, IS MORE FLEXIBLE THAN THE CONCEPT OF A REFLEX BECAUSE IT CAN BE EITHER ACTIVATED BY SENSORY STIMULI OR BY CENTRAL PROCESSES. THE TERM MOTOR PROGRAM MAY BE USED TO IDENTIFY A CENTRAL PATTERN GENERATOR(CPG). • 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.
  25. 25. LIMITATIONS •CENTRAL MOTOR PROGRAM CANNOT BE CONSIDERED AS SOLE DETERMINANT OF ACTION. •MOTOR PROGRAM CONCEPT DOES NOT TAKE INTO ACCOUNT MUSCULOSKELETAL SYSTEM AND ENVIRONMENTAL VARIABLES
  26. 26. CLINICAL IMPLICATIONS •IN PATIENTS WHOSE HIGHER LEVELS OF MOTOR PROGRAMMING ARE AFFECTED, MOTOR PROGRAM THEORY HELPS PATIENTS RELEARN CORRECT RULES FOR ACTION. •INTERVENTION SHOULD FOCUS ON RETRAINING MOVEMENTS IMPORTANT TO A FUNCTIONAL TASK, NOT JUST ON RE-EDUCATING SPECIFIC MUSCLES IN ISOLATION.
  27. 27. SYSTEMS THEORY •BERNSTEIN,1967 LOOKED AT THE WHOLE BODY AS A MECHANICAL SYSTEM, WITH MASS AND SUBJECT TO BOTH EXTERNAL FORCES SUCH AS GRAVITY AND INTERNAL FORCES INCLUDING BOTH INERTIAL AND MOVEMENT DEPENDENT FORCES. •HE ALSO NOTED THAT WE HAVE MANY DEGREES OF FREEDOM. •HIGHER LEVELS OF THE NERVOUS SYSTEM ACTIVATE LOWER LEVELS, WHILE LOWER LEVELS ACTIVATE SYNERGIES OR GROUP OF MUSCLES THAT ARE CONSTRAINED TO ACT TOGETHER AS A UNIT
  28. 28. LIMITATIONS •SYSTEMS THEORY DOES NOT FOCUS HEAVILY ON THE INTERACTION OF THE ORGANISM WITH THE ENVIRONMENT.
  29. 29. CLINICAL IMPLICATIONS •EXAMINE THE CONTRIBUTION OF IMPAIRMENTS IN THE MUSCULOSKELETAL AS WELL AS NEURAL SYSTEM. •INTERVENTION MUST FOCUS NOT ONLY ON THE IMPAIRMENTS WITHIN THE INDIVIDUAL SYSTEM, BUT AMONG THE MULTIPLE SYSTEMS
  30. 30. DYNAMIC ACTION THEORY • THE DYNAMIC ACTION THEORY APPROACH TO MOTOR CONTROL HAS BEGUN TO LOOK AT THE MOVING PERSON FROM A NEW PERSPECTIVE.(KAMM 1991, KELSO AND TULLER ,1984;KUGLER AND TURVEY1987) • THE PERSPECTIVE COMES FROM THE BROADER STUDY OF DYNAMICS AND SYNERGETIC. • “FUNDAMENTAL DYNAMIC SYSTEMS PRINCIPLE.” IT SAYS THAT WHEN A SYSTEM OF INDIVIDUAL PARTS COME TOGETHER , IT’S ELEMENTS BEHAVE COLLECTIVELY IN AN ORDERED WAY. • THIS PRINCIPLE APPLIED TO MOTOR CONTROL PREDICTS THAT MOVEMENT COULD EMERGE AS A RESULT OF INTERACTING ELEMENTS WITHOUT THE NEED FOR SPECIFIC COMMANDS OR MOTOR PROGRAMS WITHIN THE NERVOUS SYSTEM. • E.G – THOUSAND MUSCLE CELLS OF HEART WORK TOGETHER AS A SINGLE UNIT – HEART BEAT
  31. 31. DYNAMIC ACTION THEORY •DYNAMIC THEORY STATES THAT THE NEW MOVEMENT EMERGES DUE TO A CRITICAL CHANGE IN IN ONE OF THE SYSTEMS CALLED “CONTROLLED PARAMETER”.- A VARIABLE THAT REGULATES CHANGE IN BEHAVIOUR OF THE ENTIRE SYSTEM. •DYNAMIC ACTION THEORY HAS BEEN MODIFIED TO INCORPORATE MANY OF BERNSTEIN'S CONCEPTS ‘”DYNAMIC SYSTEM MODEL” SUGGESTS THAT MOVEMENT UNDERLYING ACTION RESULTS FROM INTERACTION OF BOTH PHYSICAL AND NEURAL COMPONENTS.
  32. 32. LIMITATIONS •A LIMITATION OF THIS MODEL CAN BE THE PRESUMPTION THAT THE NERVOUS SYSTEM HAS FAIRLY UNIMPORTANT ROLE AND THAT THE RELATIONSHIP BETWEEN THE PHYSICAL SYSTEM OF THE ANIMAL AND THE ENVIRONMENT IN WHICH IT OPERATES PRIMARILY DETERMINES THE ANIMAL’S BEHAVIOUR.
  33. 33. CLINICAL IMPLICATIONS • ONE OF THE MAJOR IMPLICATION OF THE DYNAMIC ACTION THEORY IS MOVEMENT IS AN EMERGENT PROPERTY. • IT EMERGES FROM THE INTERACTION MULTIPLE ELEMENTS THAT SELF ORGANIZE BASED ON CERTAIN DYNAMIC PROPERTIES OF THE ELEMENTS THEMSELVES. • MOVEMENT BEHAVIOUR CAN OFTEN BE EXPLAINED IN TERMS OF PHYSICAL PRINCIPLES RATHER THAN IN TERMS OF NEURAL STRUCTURES • CAN MAKE USE IN HELPING PATIENTS TO REGAIN MOTOR CONTROL
  34. 34. ECOLOGICAL THEORY • IN 1960S,JAMES GIBSON EXPLORES THE WAY IN WHICH OUR MOTOR SYSTEMS ALLOW US TO INTERACT MOST EFFECTIVELY WITH THE ENVIRONMENT TO PERFORM GOAL-ORIENTED BEHAVIOR. • ACTIONS REQUIRE PERCEPTUAL INFORMATION THAT IS SPECIFIC TO A DESIRED GOAL-DIRECTED ACTION PERFORMED WITHIN A SPECIFIC ENVIRONMENT. • PERCEPTION FOCUSES ON DETECTING INFORMATION IN THE ENVIRONMENT THAT WILL SUPPORT THE ACTIONS NECESSARY TO ACHIEVE THE GOAL. • ECOLOGICAL PERSPECTIVE HAS BROADENED OUR UNDERSTANDING OF NERVOUS SYSTEM FUNCTION FROM THAT OF SENSORY/MOTOR SYSTEM ,REACTION TO ENVIRONMENTAL VARIABLES TO THAT OF PERCEPTION /ACTION SYSTEM THAT ACTIVELY EXPLORES THE ENVIRONMENT TO SATISFY ITS OWN GOAL.
  35. 35. LIMITATIONS •GIVE LESS EMPHASIS TO THE ORGANIZATION AND FUNCTION OF THE NERVOUS SYSTEM THAT HAS LED TO THIS INTERACTION, MORE ON ORGANISM/ENVIRONMENT INTERFACE
  36. 36. CLINICAL IMPLICATIONS • A MAJOR CONTRIBUTION OF THIS VIEW IS IN DESCRIBING THE INDIVIDUAL AS AN ACTIVE EXPLORER TO THE ENVIRONMENT. • AN IMPORTANT PART OF INTERVENTION IS HELPING THE PATIENT EXPOLRE THE POSSIBILITIES FOR ACHIEVING A FUNCTIONAL TASK IN MULTIPLE WAYS • THE ABILITY TO DEVELOP MULTIPLE ADAPTIVE SOLUTIONS TO ACCOMPLISH A TASK AND DISCOVER THE BEST SOLUTION FOR THEM, GIVEN THE PATIENTS SET OF LIMITATIONS.
  37. 37. WHICH IS THE BEST THEORY OF MOTOR CONTROL •THE BEST AND MOST COMPLETE THEORY OF MOTOR CONTROL, THE ONE THAT REALLY PREDICTS THE NATURE AND CAUSE OF MOVEMENT AND IS CONSISTENT WITH OUR CURRENT KNOWLEDGE OF BRAIN ANATOMY AND PHYSIOLOGY? •THERE IS NO ONE THEORY THAT HAS IT ALL •BEST THEORY-THAT COMBINES ELEMENTS FROM ALL THE THEORIES PRESENTED
  38. 38. NEUROLOGIC REHABILITATION: REFLEX BASED NEUROFACILITATION APPROACHES • NEUROFACILITATION APPROACHES INCLUDE BOBATH(KARL AND BERTA BOBATH,1965), THE ROOD APPROACH(MARGARET ROOD,1967), BRUNNSTROM APPROACH(SIGNE BRUNNSTROM,1966) , PNF(VOSS,1985) , SENSORY INTEGRATION THERAPY(JEAN AYRES,1972). • THESE WERE BASED ON ASSUMPTIONS DRAWN FROM BOTH THE REFLEX AND HIERARCHICAL THEORIES OF MOTOR CONTROL. • THEY FOCUS ON RETRAINING MOTOR CONTROL THROUGH TECHNIQUES DESIGNED TO FACILITATE AND/OR TO INHIBIT DIFFERENT MOTOR PATTERNS
  39. 39. CLINICAL IMPLICATIONS • EXAMINATION OF MOTOR CONTROL SHOULD FOCUS ON IDENTIFYING THE PRESENCE OR ABSENCE OF NORMAL AND ABNORMAL REFLEXES CONTROLLING MOVEMENT. • INTERVENTIONS SHOULD BE DIRECTED AT MODIFYING THE REFEXES THAT CONTROL MOVEMENT • THE IMPORTANCE FOR SENSORY INPUT FOR STIMULATING NORMAL MOTOR OUTPUT SUGGESTS AN INTERVENTION FOCUS OF MODIFYING THE CNS THROUGH SENSORY STIMULATION
  40. 40. TASK-ORIENTED APPROACH • BASED ON NEWER THEORIES OF MOTOR CONTROL • IT IS ASSUMED THAT THE NORMAL MOVEMENT EMERGES AS AN INTERACTION AMONG MANY SYSTEMS. • MOVEMENT IS ORGANIZED AROUND A BEHAVIORAL GOAL AND IS CONSTRAINED BY THE ENVIRONMENT. • CLINICAL IMPLICATION - TASK ORIENTED APPROACH TO INTERVENTION ASSUMES THAT PATIENTS LEARN BY ACTIVELY ATTEMPTING TO SOLVE THE PROBLEMS INHERENT IN A FUNCTIONAL TASK RATHER THAN REPETITIVELY PRACTICING NORMAL PATTERNS OF MOVEMENT

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