Behavioral Theories of Motor Control Chapter 3

Coordination and Control Degrees of freedom (problem) (Bernstein,1967) Number of independent elements (nerves, muscles, and joint movement possibilities) that must come together into an organized movement pattern Coordination (Sparrow, 1992; Turvey, 1990) Process of constraining the system’s available degrees of freedom into a movement pattern Control Manipulation of those variables within the movement to meet the demands of a given situation …..need both coordination and control in the acquisition and performance of motor skills (Vereijken, Whiting & Beek, 1992)

Command Center (theories regarding brain’s contribution to skilled movement) Motor Program Abstract representation of a movement plan Stored in memory Issues instructions that are carried out by the limbs and muscles When a specific action is required, it is retrieved from memory and executed

Early Motor Program Theories Proposed that for each movement to be made, a separate motor program existed and was stored in memory 2 problems: Storage (would need limitless space in memory) Novel responses (when you need to do something NEW)

Generalized Motor Program (GMP) (Schmidt,1985) Represents a class of actions or pattern of movement that can be modified to yield various response outcomes Invariant features Relatively fixed underlying features that define a GMP Parameters Flexible features that define how to execute a GMP, easily modified from one performance to another

Invariant Features Relatively fixed underlying features (eg.fingerprints) Sequence of actions or components (e.g. order of actions to perform a tennis serve) Relative timing Internal rhythm of the skill (e.g.-arm movement in freestyle) Relative force Internal force relationship (changes proportionately as force increases or decreases)

Parameters Adaptable features of program Easily modified from one performance to another to produce variations of a motor response (e.g. ability to throw to 1st base from various parts of the softball field) Overall duration Overall force Muscle selection For example, a soccer player can make a long or short pass, as the situation requires - same basic pattern but different outcome.

Schema (Schmidt, 1975,1985) Rule or relationship that directs decision-making when a learner is faced with a movement problem - is the result of accumulated experiences Developed by abstracting 4 sources of information each performance attempt Initial conditions (limb/body/environmental conditions) Response specifications (parameters e.g. speed/force required for the throw/ kick/ pass etc…) Sensory consequences (sensory feedback - how it felt) Response outcome (relative success of the action)

Motor Response Schema Recall schema Responsible for organizing the motor program Based on relationship with past experience of the action Recognition schema Responsible for the evaluation of a movement attempt Both schemas can be ‘fine tuned’ with sensory feedback and external feedback (from the teacher/ instructor)

Open Vs. Closed Loop Systems Open loop Action plans generated by command center then carried out by the limbs and muscles without modification (feedback can only be used to vary a subsequent attempt at the movement action) Closed loop Command center generates action plan that initiates the movement Feedback be used to modify on-going action Action can be changed whilst it is occurring Not possible in actions that involve speed

Evidence Supporting Motor Program Control As complexity of the movement increases, RT increases (Henry & Rogers,1960) Deafferentation studies involving surgical severing of sensory nerves (e.g. Polit & Bizzi, 1978) Effects of unexpectedly blocking a limb during movement (Wadman, Dernier van der Gon, Geuze & Mol, 1979) For example, baseball batter infers a specific type of pitch due to the type of wind-up demonstrated by the pitcher BUT the pitcher adjusts the way the ball leaves the hand, just prior to release - too late for the batter to adjust the motor program and therefore misses the ball!!

Dynamic System Theory Argues that other theories ignore the fact that movement occurs in response to dynamic interaction of the mover and the environment Alternatively, movement pattern is thought to emerge or self-organize as a function of the ever-changing constraints placed upon it

Constraints (Caldwell & Clark,1990) The boundaries that limit the movement capabilities of an individual Three types (or combination of each) Organismic: can be structural e.g. height or functional e.g. cognitive ability Environmental: eg. gravity, temperature, wind speed Task: eg goals of the task, rules of the task, implements or machines required

Attractor States Systems prefer states of stability When a change in constraints is imposed on a system, its stability is endangered Deep basins = well learned = stable systems = difficult to change (Ennis, 1992) Shallow basins = patterns not set = less stable = more susceptible to change

Phase Shifts Changes in behavior are the result of a series of shifts Control parameters Variables that move the system into new attractor states (e.g. direction, force, speed, perceptual information) Rate limiters E.g. cricket bat too heavy for the child) Constraints that function to hinder or hold back the ability of a system to change

Dynamic System Theory Synopsis The complexity of human behaviour leads to the Dynamic System Theory (DST) approach to understanding motor control Teachers/ instructors need to: Know individual learners’ capabilities; Understand the complexity of the task to be taught; ‘Break down’ the task into developmentally appropriate stages; Minimise or allow for constraints evident when teaching skills; Understand the effect of ‘prior learning’ and ‘unlearning’; Ensure the environment is conducive to learning;