Theories and Problems Flashcards
What is a theory?
- Accurately describes a large class of observations.
- Makes definite predictions about results of future observations. (hawking)
What does motor learning and control theories focus on?
- Explaining human movement behavior
- Providing explanations about why people perform skills as they do.
How does a theory have relevance to professional practice?
- Provides the “why” basis for what practitioners do.
What does motor control theory describe?
- Describes and explains how the nervous system produces coordinated movement during motor skills performance in a variety of environments.
What is science?
- A tool to utilize and explain scientific experiments or observations to falsify claims about the world.
Two types of control systems
- Closed-Loop Control
- Open-Loop Control
Control System
- How are you controlling different parts of your body?
- Stimulus
- Sensor or receptor
- Afferent pathways
- Integrating center
- Efferent pathways
- Target or Effector
- Response
Open and Closed Loop control System
- Each has a central control center (executive)
- Each include instructions form control center to effectors.
Differences between the two systems?
- Open loop
a. Does not use feedback
b. Control center provides all the information for effectors to carry out movement. - Closed loop
a. Uses feedback
b. Control center issues information to effectors sufficient only to initiate movement
-Relies on feedback to continue and terminate movement
Application of Closed Loop Control
- Feedback and error are key
- Untrained Skills
- High attentional demands
Application of open loop control
- Pre-program responses
- Quick and reactive
- Low attention
- No Feedback
Cerebellum
- Reference mechanism
Open/Closed Loop continuum: Fitt’s law
- Showed we could mathematically predict movement time (MT) for speed- accuracy skill
- The MT increases with either increasing the movement amplitude (A) or decreasing the target width (W)
Speed accuracy trade off
- When both speed and accuracy are essential to perform the skill.
Open-loop control: At movement initiation
- The initial movement instructions sufficient to move limb to the vicinity of the target.
- Speed, direction and accuracy are under CNS command
Closed-loop control: At movement termination
- Feedback information needed to terminate the movement
- Feedback from vision and proprioception needed at end of movement to ensure hitting target accurately.
Motor Program Based Theory
- Cognitive based mechanism that controls coordinated movement
Dynamical Systems Theory
- Emphasizes the role of information in the environment and mechanical properties of the body and limbs in movement control/coordination.
Generalized Motor Program (GMP)
- Hypothesized memory based mechanism responsible for adaptive and flexible qualities of human movement.
a. Proposed that each GMP controls a class of actions, which are identified by common invariant characteristics
GMP Function
- To serve as the basis for generating movement instructions prior to and during the performance of an action.
Invariant Features
- Characteristics that do not vary across performances of a skill within class of actions.
- The identifying signature of a GMP
Parameters
- Specific movement features added to invariant features to adapt a specific situation
- Characteristics can very from one performance of a skill to another.
Dynamical Systems Theory (DST)
- Describes the control of coordinated movements by emphasizing the roles of environmental information and dynamic properties of the body/limbs.
Genesis of DST
- DST was attempting to resole two problems associated with cognitive based theories.
- Context-conditioned variability problem
- Degrees of freedom problem
Context-Conditioned Variability Problem: Cognitive based theories
- Specific movement outcomes are dependent on specific commands found the motor program.
Degrees of freedom problem
- DOF: Number of ways in which a system can independently vary
a. Same goal can be achieved by different movements.
Solutions to the problems (Synergies)
- Clustering of degrees of freedom into cooperating collectives.
- Temporary and flexible assembled functional organizations that are defined over a group of muscles and joints and the convert those components into task specific coherent multiple degrees of freedom ensembles
Freezing the degrees of freedom
- Limiting the movement of limbs and joints.