Motor Development – Dynamic Systems Theory – Flashcards

Based on a neuro-maturational, hierarchical view of development The approach is to change the motor impairment, inhibit and integrate primitive postural patterns and facilitate normal movement patterns. Children are discouraged from performing activities that use abnormal movement patterns Bobath's concepts evolved as new evidence emerged

1) CNS alone is inadequate to understand movement 2) Must consider other influences -Mechanics of the system -External and internal forces -Environment -Task 3) A distributed systems concept - not just the CNS

1) Human movement is complex (many elements) 2) Consider the number of degrees of freedom (df) in the upper limb that contribute to movement 3) Does our system control individual muscles, synergistic muscle group activity, stiffness of each muscle timing of muscle activity for each limb segment? 4) Motor units, muscles, axes of movement, segments 5) This is known as the "degrees of freedom" problem, a lot of elements to control 6) How can our system control all these df and produce accurate movement quickly?

Movement patterns emerge from synergistic organization of the neuromuscular system based on: Morphological Factors - biological constructs Biomechanical Factors - Newtonian Environment - spatial/temporal Task - walking fast or slow

Movement is _____________, involves coupling of degrees of freedom - muscles and neuropathways to to achieve functional outcome.

Environment - Child with CP has same nervous system but can perform better riding a horse compared to walking (or not walking) on land.

Degrees of freedom Self organizing behavior Stability/Instability (sign of learning, indicates change) Phase transitions Order parameters Control parameter

Stability - Patient post stroke, walks with hyperextended and circumducted gait Instability - change environment or task constraints (pool, treadmill) Leads to more variability - exploring more ways of performing movement (Good)

Aspect of movement that is required to be control Constrain stroke patient at knee with AFO and assess whether new gait pattern holds without brace

Order - that which defines the task (Walking) Control - that which changes the task (water, treadmill, obstacles)

- Necessary and permissive conditions TM walking in infants (Thelen, Ulrich) Kitten walking & paw shake (Bradley) Chicks hatching (Bekoff) Frog locomotion (Stehouwer)

Exhibit periods of STABILITY and INSTABILITY Stable - preferred patterns of movement Change of pattern is characterized by instability Skill acquisition is a series of stable and unstable states and phase transitions During instability the "system" explores new coordination modes or solutions Small forces or changes can have a large effect on behavior - non linear effects Examples: Infant locomotion progression, improving golf swing, playing an instrument, others

Occurs during periods of exploration or instability Variability forces exploration of new solutions Exploration and selection are key elements to learning Examples Jolly Jumper (Goldfeld) Mobile (Rovee-Collier)

Is there one variable that defines the movement? What makes walking walking? What would you measure that you know it is walking. In phase/ out of phase example

Characteristics of the movement Lowest dimension that defines the dynamic state Example: phase relationship of lower limb segments is the order parameter for gait, jumping, skipping, etc. (Kurz, 2004) Example: think of a trotting horse and a galloping horse Others

One parameter in the system can change stable behavior by increasing variability/producing instability and force change in behavior. Bifurcation. A situation where a very small increase or decrease in the value of some parameter controlling the system causes it to change rather abruptly from one type of behavior to another

Gait velocity - obstacle height, change in support surface Growth - segment length, mass, and distribution Sensory development or degradation - vision, perception etc. Experience - task and environment Practice - amount and variability Environment - adequate and permissive conditions

Freeze Degrees of Freedom Release Degrees of Freedom with increase skill Example: Stroke patient with circumduction gait

Variability is a sign of adaptability Adaptability is a sign of health Disease typically decreases complexity (CHF, stroke, CP) Variability of breathing pattern (ApEn) has been used to evaluate risk for SIDS Seizures

Many muscle synergies used at 3-4 months Predominant synergies emerged at 4-6 months of age (Harbourne and Giuliani) Children acquire independent sitting with environmental conditions Effects of environment on emergent behaviors Effects of practice on sitting patterns (Scalise-Smith and Giuliani)

1. Lyapunov exponent (LyE): measurement of instability Instability indicates learning a new behavior (Harbourne, 2003) Instability as pathology (Buzzi, 2003) Larger values indicate less organized (increased instability) 2. Approximate Entropy (ApEn): Measurement of complexity, used with time series data Larger values indicate increased complexity