Motor Control Intro to Theoretical Perspectives & Rehabilitation Models

Motor Control

an area of study dealing with the understanding of the neural, physical, and behavioral aspects of movement

ability to regulate or direct the mechanisms essential to movement

information processing

use of sensory input, motor output and central integrative structures to produce coordinated movement behaviors

Stages of processing

1. Stimulus ID

2. Response Selection

3. Response Programming

Stimulus ID

decide whether a stimulus has presented and, if so, what it is

if you hand them a marker do they know what it is, do they know how to use it

Response selection

decide what response to make, given the nature of the situation and environment —> what to do and how to do it

Motor Plan

They know it’s a marker and you use it to write but how are they going to grab it and write

Response Programming

prepare the motor system to make the desired movement

Motor Program

serial processing

a specific, sequential order of processing info

parallel/distributed processing

processing of info that can be used for more than 1 activity by more than 1 center simultaneously; allows dual task performance

movement output

response execution; influenced by feedforward and feedback

theories of motor control

reflex theory

hierarchical theory

systems theory

Reflex theory

based on work of Sir Charles Sherrington; Studied reduced cat preparations (ablated above midbrain)

Reflexes are the basis for all movement

chains of reflexes result in normal movement

the nervous system is a passive recipient of sensory stimuli that triggers, coordinates, and activates muscles

“peripheralist”

Limitations of reflex theory

does not adequately explain spontaneous and voluntary movements

reflex cannot be the basis of all motor behavior if an outside stimulus is not required to initiate movement

movement is possible in the absence of sensory input

does not adequately explain fast/ballistic movement that occurs too rapidly for the use of sensory feedback to trigger next movement

reflex chains do not adequately explain the variation in responses that may occur from the same stimulus

reflexes do not explain the ability to produce novel movements based on experience (violinist playing a cello)

Hierarchical theory

based on the work of JH Jackson

control organized hierarchically —> top down

voluntary movements initiated by “will” (higher levels")

reflexive movements described as primitive (childlike); eventually inhibited by higher motor centers

“Centralist”

low level primitive reflexes “block” higher coordinated movement patterns

• negative signs = loss of function; weakness

• positive signs - release of previously suppressed abnormal reactions (spasticity)

Hierarchical theory limitations

cannot explain the dominance of reflex behavior (low level) in certain situations in normal adults (e.g. stepping on a pin —> immediate reflex; bottom-up control)

not all movement is initiated from higher centers

cannot assume that all low-level behaviors are primitive, immature and non-adaptive, while all higher level/cortical behaviors are mature adaptive and appropriate

• Central motor pattern/motor program

• central pattern generators (CPGs)

Central Motor Pattern / Motor Program

more flexible than the concept of a reflex because it can be activated either by sensory stimuli or by central processes

Central pattern generators (CPGs)

spinally mediated motor programs; research in cat models found CPGs by themselves can generate complex movements as they walk, trot, and gallop

Systems theory

based on work of Russian neurologist Nikolai Bernstein; described as distributed control system

movements not peripherally or centrally driven; strategies of motion emerge from dynamic interaction among many systems — each contributing to different aspects of control

• influenced by internal factors (joint stiffness, inertia, forces) & external factors (gravity)

the language we want to use as Contemporary PTs

synergies

constantly modifies control for most effective and efficient means to meet task goals (closed loop)

Task-oriented

Limitation of the System Theory

considered the contributions of the nervous system, skeletal system, gravity and inertia to predict motor behavior — did not explore other environmental factors, cognitive/perceptual influences and open loop control

many variations of a “systems” model have developed creating some confusion with terminology and application

Neurologic rehabilitation models

Muscle Re-education model

Neurotherapeutic Facilitation model

Contemporary Task-Oriented model

Muscle Re-education Model

Sister Kenney for tx of poliomyelitis

Not based on a neurophysical motor control model, but knowledge of gross muscle anatomy and on faith in human willpower

Focused on use of manual muscle testing to identify weakened muscles and specific exercise to strengthen isolated muscles (“re-education”)

assumes that patients can consciously channel their neural energy to activate individual muscles and motor units (like biofeedback) when provided with appropriate feedback

avoids secondary complications and ineffective, inefficient compensatory movement patterns

provides bracing to correct/prevent deformity — ortho focus

Neurotherapeutic Facilitation Model

developed by therapists and physicians including Karl and Bertha Bobath, Kabat, Knott and Voss, Stockmeyer and Brunnstrom

based on reflex and hierarchical models of motor control

Common Assumptions:

1. The brain controls movement not muscles

2. We can alter, or facilitate, a patient’s movement patterns by applying specific patterns of sensory stimulation, especially through procioceptive afferent pathways

3. The CNS is hierarchically organized, with higher centers normally in command of lower centers, which in turn control primitive and more automatic behaviors

4. Recovery from brain damage follows a predictable sequence that mimics the normal development of movement during infancy

5. Primary of the neurophysiological explanation (assumes that abnormal movement patterns are the direct result of the neural lesion)

Primary aims:

• Facilitate normal movement & inhibit abnormal tone and primitive reflexes

• progress through the developmental sequence

• use manual guidance to correct movement patterns

  • prevent errors/abnormal movement

Contemporary Task-Oriented Model

Evolving based on recent models and research in the areas of motor control and motor learning; began to emerge in 80-90s

II Step— addressed contemporary knowledge base in science of motor behavior and how to incorporate these new concepts into PT education and practice

III Step — addressed the integration of neuroscience and clinical practice; emphasis on evidence-based practice

IV step — Themes of: Prevention prediction, plasticity and participation

Based on Systems Model of Motor Control

Targets both the peripheral and central systems to influence motor control

Assumes that control of movement is organized around goal-directed functional behaviors

Assumes that control of movement is organized around goal-directed functional behaviors

Training not limited to “normal” patterns, but allows patients to learn alternative movement strategies to coordinate motor behaviors as efficiently as possible

Training specificity