Motor Control Theories PDF

Neuro-Rehabilitation Theories Motor Control Gabriel Kwame Fienya, MSc, DPT, MCSP 1 Lecture objective  Lecture objective v Explain the concept of Motor Control. v Review the theories of Motor Control. v Discuss Rehabilitation Implications of Motor Control Theories 3...

Neuro-Rehabilitation Theories Motor Control Gabriel Kwame Fienya, MSc, DPT, MCSP 1 Lecture objective  Lecture objective v Explain the concept of Motor Control. v Review the theories of Motor Control. v Discuss Rehabilitation Implications of Motor Control Theories 3 Introduction  Introduction v Entire range of human activity depends on motor system coordinating the actions of the musculoskeletal system v Motor Control is a complex process that involves the brain, muscles, limbs, and often external objects. v It underlies motion, balance, stability, coordination, and our interaction with the environment and others 5 What is Motor Control  What is Motor Control v The study of human movement and the essential mechanisms that regulate the performance of a motor skill. v Why Should Therapists Study Motor Control? 7 Motor Control v The ability to stabilize the body in space -Postural Control v The ability to coordinate bodily segments in space -Motor Coordination v Motor control allows the nervous system; v Direct which muscles should be used v In what order v To solve a movement problem  Control Circuit v The activity of the motor path way is regulated by two control circuits 1. Basal ganglia – selection and initiation of specific motor program 2. The cerebellum – controls the execution of the motor acts and motor learning 9 Structures Involved in Motor Control 1. An Intact Nervous System v Central program generators - cerebral cortex, basal ganglia and spinal cord v Postural control and stability - basal ganglia, cerebellum v Control of recruitment - corticospinal tract v Appropriate postural tone to meet environmental demands v Final common pathway out to the muscles  Structures Involved in Motor Control 2. An intact musculoskeletal system 3. Appropriate biomechanics and alignment of body segments 4. Sensory and perceptual processing 5. Cognitive function 6. Motivation and emotion 7. Motor learning and motor planning abilities 11 The Nature of Movement v Movement emerges from the interaction of three factors – Individual – Task – Environment v Person’s functional capacity -  Individual Factors 13 Individual Factors v Motor/Action Systems - Motor output from the nervous system to the effector system (muscles) v Sensory/Perceptual Systems - integration of sensory impression into psychological meaningful information v Cognitive Systems - attention, planning, problem solving, motivation, and emotional aspects of motor control that underlie the establishment of intent or goals.  Task Factors 15 Individual Factors  Classification Scheme for Different Types of Movement Tasks 17 Classification Scheme for Different Types of Movement Tasks DISCRETE TASKS CONTINUOUS TASKS  Classification Scheme for Different Types of Movement Tasks CLOSED TASKS OPEN TASKS 19 Classification Scheme for Different Types of Movement Tasks STABILITY MOBILITY  Classification Scheme for Different Types of Movement Tasks MANIPULATION TASKS 21 Classification Scheme for Different Types of Movement Tasks FINE MOTOR SKILLS GROSS MOTOR SKILLS  A Taxonomy of Tasks Combining Stability–Mobility and Closed–Open Task Continua 23 How would you classify the following actions? v A CVA patient standing upright in a queue at a popular trotro station v A patient with crutches walking on a corridor in a busy outpatient department of a hospital. v An elderly woman crossing a busy street at Makola. How would you classify the following actions? v A professor walking from his car to supermarket door, pushing the grocery cart across a busy parking lot v A househelp ringing a doorbell v A cook stirring hot coffee with a spoon 25 Environmental Factors Environmental Factors v We need to prepare our patients for coping in a wide variety of environments v Therefore need to understand the features of the environment and their impact on movement v Need to Understand Attributes of the environment that affect movement 27 Environmental Factors  Environmental Factors: Regulatory Conditions v Aspects of the environment that shape the movement – Eg the size, shape, weight of an object (eg picking up a cup) or the surface that we walk on (hard, soft, slippery,sloping) 29 Environmental Factors: Non-Regulatory Conditions v Affects performance but movement does not have to conform to these features – Eg: background noise, distractions, etc  Implications for Rehabilitation 31 The Person: v Consider the functions/ tasks that are important to the individual v Consider their abilities and limitations v Analyse missing components and underlying reasons for functional problems The Task: v In assessment, therapist needs to analyse the requirements of the task v When movement is retrained in relation to a specific task, treatment is most effective i.e. task specific exercise 33 The Environment: v Will affect motor performance of your patient v Need to consider it in your assessment and treatment v Can be manipulated to make the task easier or more difficult eg. -Raise plinth for sit to stand -Gait practice over uneven ground, in busy environment, or with obstacles etc.  Theories of Motor Control 35 What is a Theory? v A theory is a set of abstract facts and observations. v Hypotheses are generated and tested. v Theories develop over time to reflect scientific knowledge Theories of Motor Control (MC) v Explain how the nervous system generates movement. v Theories provide a framework for; v Generating new ideas v Interpreting motor behaviour v Guiding clinical actions v Working hypothesis for examination and intervention. 37 Theories of Motor Control (MC) v Reflex Theory v Hierarchical Theory v Systems Theory  Reflex Theory 39 Reflex Theory – (Sherrington) v Sir Charles Sherrington, a neurophysiologist in the late 1800s and early 1900s v reflexes were the building blocks of complex behavior v complex behavior could be explained through the combined action of individual reflexes that were chained together Reflex Theory: Assumptions v Sensation is NECESSARY for movement v Sensory inputs controls motor outputs v Reflexes are the basic units of Complex behavior (Reflex Chaining) 41 Reflex Theory The basic structure of a reflex consists of a receptor, a conductor, and an effector.  Reflex Theory: Rehabilitation Implications v Could allow therapists to predict function v Movement behaviour could be interpreted in terms of the presence or absence of controlling reflex v Retraining motor control for functional skills would focus on enhancing or reducing the effect of various reflexes during motor task 43 Reflex Theory: Limitations v the reflex cannot be considered the basic unit of behavior if both spontaneous and voluntary movements are recognized as acceptable classes of behavior, because the reflex must be activated by an outside agent. v reflex theory of motor control does not adequately explain and predict movement that occurs in the absence of a sensory stimulus.  Reflex Theory: Limitations v the theory does not explain fast movements, that is, sequences of movements that occur too rapidly to allow for sensory feedback from the preceding movement to trigger the next. v the concept that a chain of reflexes can create complex behaviors fails to explain the fact that a single stimulus can result in varying responses depending on context and descending commands. v reflex chaining does not explain the ability to produce novel movements. 45 Hierarchical Theory  Hierarchical Theory: -(Jackson 1932) v characterized by a top-down structure, in which higher centers are always in charge of lower centers. HIGH LEVEL (Frontal Cortex) MIDDLE LEVEL (Motor Cortex, Association Areas, Brain stem) LOW LEVEL (Spinal Cord) 47 Hierarchical Theory: -(Jackson 1932)  Hierarchical Theory: Assumptions v – The brain controls all movements v – The higher centers inhibit reflexes controlled by lower centers v – Suppressed reflexes emerge after brain injury 49 Hierarchical Theory: Assumptions v Neuromaturation drives motor development and postural control v CNS links together contractions of different muscles to produce synergies.  Hierarchical Theory: Rehabilitation Implications v Abnormal movements results from lack of brain inhibition v Reflexes were tested to help predict CNS maturation and to predict function v Facilitate and inhibiting abnormal reflexes - Movement patterns and handling (PNF) v Recovery follows a developmental sequence. -Train patients through this sequence (NDT) v Functional skills will automatically return. 51 Hierarchical Theory: Limitations v Normal adults exhibit primitive reflexes - Withdrawal reflexes (flexor) v Inhibition of reflexes does not produce normal movement v Non-CNS factors influence movement v Patients are passive recipients of treatment  Systems Theory 53 Systems Theory- (Bernstein-1970’s) v you cannot understand the neural control of movement without an understanding of the characteristics of the system you are moving and the external and internal forces acting on the body v external forces such as gravity and internal forces such as both inertial and movement-dependent forces. v same command could result in different movements and different commands could result in the same movement  Systems Theory- Assumptions v Control is Distributed v Motor control is organized around a behavioral goal v Movement is an emergent property v interaction among many systems v The individual, task and environment v Perception, cognitive and action (motor) processes 55 Systems Theory- Rehabilitation Implications v Therapists should practice goal oriented tasks v Motor problem solving v Vary the task and environment v Improve movement efficiency v Consideration of all possible systems - Changes in movement capacity are not necessary due to NS problems  Systems Theory- Limitations v Minimizes “hands-on” v Cognitive demanding v Time consuming (repetition) v Difficult to quantify efficient movement 57 Systems Theory-Based Treatment Approaches v Dynamic Action Theory v Motor Programming Approach v Ecological Approach v Task oriented Approach Summary (PNF, NDT, Brunntrom, Sensory Integration) (Function, Strategy) 59 Neuroplasticity: Theory of Recovery Neuroplasticity: Theory of Recovery v Rehabilitation interventions that are successful capitalize on behavioral stimulants of positive neuroplastic change 61 Neuroplasticity v Ability of the brain to adjust itself functionally, by reorganizing the cortical maps and reorganize itself by forming new neural connections throughout life. v This capacity for rewiring of the neuronal synapses to allow for re-development of entire regions of the brain is present in adults as well as children Mechanisms for Neuroplasticity v Enhancement of existing pathways v Synaptic strengthening v Formation of new pathways v Collateral sprouting v Unmasking of latent connections v Neurogensis 63 Understanding the Mechanism v Commonly, these rearrangements involve changes in the connection between linked nerve cells, or neurons, in the brain. v Brain reorganization takes place by mechanisms such as "axonal sprouting", where undamaged axons grow new nerve endings to reconnect the neurons, whose links were severed through damage. Understanding the Mechanism v Undamaged axons can also sprout nerve endings and connect with other undamaged nerve cells, thus making new links and new neural pathways to accomplish what was a damaged function. v Although the developing brain is clearly more plastic than the adult brain, v neuronal connections are continuously remodelled by experience and by performance of specific and complex movements during motor and cognitive learning, and memory processes involve brain plasticity. 65 Understanding the Mechanism v Rapid and transient alteration of cortical representation areas are seen during learning tasks, most likely related to unmasking of previously existing connections, v - perhaps as a result of decreased inhibition and increased synaptic efficacy in existing neuronal circuits. v Whereas each brain hemisphere has its own tasks, if one brain hemisphere is damaged, the intact one can sometimes take over some of the functions of the damaged one. Understanding the Mechanism v Flexible and capable of such adaptation, the brain compensates for damage in effect by reorganizing and forming new connections between intact neurons. v New connections can form at an amazing speed, but in order to reconnect, the neurons need to be stimulated through activity. 67 Other Role of Plasticity v Deleting old connections as frequently as it enables the creation of new ones. v Through this process of “synaptic pruning,” connections that are inefficient or infrequently used are allowed to fade away, while neurons that are highly routed with information will be preserved, strengthened, made even more synaptically dense. Changes in Synaptic Strength v Long Term Potentiation v Long Term Depression 69 Principles Governing Neuroplasticity Principles to Induce Plasticity in Rehabilitation v Training specificity v Practice using typical movement patterns v Repetition of desired movement v Focused attention 71 Principles to Induce Plasticity in Rehabilitation FIRST PRINCIPLE v Body Parts Compete for Brain Representation; v The more a body segment is used, the bigger its representation in the brain - correlates with improved function v The opposite results in ‘’learned non-use’’ 73 SECOND PRINCIPLE v Both the Ipsilateral and Contralateral portions of the brain can contribute to motor control v If one hemisphere gets damaged, the intact hemisphere may take over some of its functions v For functional recovery to occur, neurons have to be stimulated through activity. THIRD PRINCIPLE v Sensory stimulation enhances neural reorganization. v Sensory stimulation enhances the sensory representation of the body part being stimulated. v It causes that area of the brain to be hyperexcitable to change. 75 FOURTH PRINCIPLE v Reduction of inhibitory agents promotes brain reorganization v Removal of factors that make patients more sleepy or less motivated promotes the capacity of the CNS to adapt to functional demands v Treat depression but don’t use medications that induce drowsiness. FIVE PRINCIPLE v Pharmacological Agents enhances the brains ability to reorganize itself and adapt to functional demands v You can have your patients take the medications to improve recovery after neurological insults. 77 Practice Variables & Neuroplasticity v Practice/Repetition (Jenkins et al., 1990) v Task Difficulty/Intensity (Plautz, Milliken, and Nudo, 2000) v Task Complexity (Jones et al., 1999) v Functional reorganization of motor cortex: v Skill dependent rather than use dependent. v Skill acquisition is more important than movement repetition. Implications for Rehabilitation v Strengthen synaptic activation v Provide adequate sensory input v Promote skill acquisition v Use evidence-based skill acquisition strategies v Deliver treatment at optimum time v Early treatment post injury facilitates neuroplasticity v Educate people 79 What we can do to promote recovery in our patients v PROMOTE USE OF IMPAIRED BODY SEGMENTS; IMPAIRED SYSTEMS v Utilize Experience-Dependent Practice Variables in the clinic v Task Intensity v Task Specificity v Repetition  THANK YOU ANY QUESTIONS ?? 81