EXPH 2106 - Theories of Motor Control

Scientific Theory

Statement / set of statements that relates observations about a specific phenomenon in a coherent, logical, and testable way

Accounts for a large class of observations based on only a few simple propositions (Simple explanations are the best!!)

Makes defined predictions about the results of future observations (testable)

Theories to control body to produce skilled movements and training principles

Dynamical systems

Closed loop

Open loop

Motor Program Theory

Cognitive structures responsible for skilled movements. Since skills can be learned and retained, they must somehow be represented within memory

Located in the CNS

Control and learning occur here

Hierarchically arranged

Top: Brain

Brain stem and thalamus

Down: Motor and sensory neurons

Closed Loop Motor Control Key Components

Skilled movement

Underlies movements that are relatively slow and deliberate (Doing it on purpose and pay attention to feedback)

Movement is initiated based on previous experience (Idea of what's correct)

- Feedback is then used to adjust movement for this particular action

Skilled movement

Needs feedback, error detection (cerebellum), and error correction

- Implies a reference for correctness /desired performance

Closed Loop

Sensory input that modulates motor output

Feedback

Modifies things as you go

Closed loop control examples

- Balance platform with feedback of COM and movement with corrections

- Threadding the needle with depth perception

- Parallel parking (Checking everything out)

Advantages of Closed Loop Control

Appropriate for unpracticed skills (trial and error, lots of mistakes) (USE FEEDBACK HERE)

Allows movements to be corrected once they've begun

- = adaptability

Can produce precise and accurate movements (continuous and fine motor skills)

Disadvantages of Closed Loop Control

Attention-demanding

Time required to prepare and execute successive corrections to an ongoing action - too slow for fast skills (discrete, ballistic skills)

- Baseball pitch example (Quick movements and NOT enough time for feedback to work)

Adam's Closed Loop Learning Theory

Memory trace and perceptual trace

Brain picks up memory trace with movements learned and each skill has its own pathway

Memory trace

Selects &initiates desired action

- Specific to each skill

Perceptual trace

Evaluates the correctness of the action executed by the memory trace

- Practice repetitions & augmented feedback important to reinforce pathway

What happens when picking the right trace?

More facilitatory neurons and myelin to increase trace

Adam's Closed Loop Learning theory comments

- Perfect practice

- Practice correct movement to reinforce correct movements

Adam's Closed Loop Learning theory criticisms

Novelty / motor equivalence problem

- How is a specific skill performed well the first time? (memory trace comes from practice..)

Modifiability problem

- What mechanisms are responsible for controlling action once initiated by the memory trace?

Storage problem (Hard for every movement to have an unique, own pathway)

Open Loop Motor Control

All pre-planned and press play to execute plan

Motor programs contain a complete set of instructions for their execution (NOT pathway)

Environmental information is used to prepare the motor systems for action= feed forward (Solves problem when moving fast, quick, automatic)

Applies to skills that are performed quickly and automatically

Open Loop Examples

Skiing and cup stacking

Advantages of Open Loop System

Capable of producing quick movements

Attentional resources can be directed toward other tasks

Disadvantages of Open Loop System

Not effective for skills that are unpracticed or not well-learned (Hard for movements completing for the first time)

Not as effective in changing environments

Schmidt's Schema Theory - Motor Learning

Schema

Movement class

Schema (Motor plan)

A generalized motor program that represent an entire class of similar skills = "movement class"

Movement class

All the different ways a skill might be performed while following the same rules (Walking and different ways to walk)

Variant vs. Invariant features

Invariant features

components of movement production that do not change = "RULES"

NOT variable

Variable features

Variant features: flexible components of a motor program

- Define how to execute the program under different conditions

- Easily modified, adaptable (Still fits in category and don't change invariant rules)

Invariant features

Sequencing of components (Parts of body going in to executing movements)

Relative timing

Relative force

Motor program : Signature

Can make same shape with lots of different muscles of the body

Dance Schema: Invariant features

Rumba, Swing dancing and Waltz

Steps, sequences, directions, etc

Variant features

Overall duration (Fast / slow)

Overall force / amplitude (Big / small)

Muscle selection (Handwriting example)

Environment and object

Lindy hop example

Basic

- Invariant features (schema)

- Step-step-triple step

Advanced

- Variant features

- Turns, changes in direction

Variability of Learning Hypothesis

More variability in practice provides more information for abstracting RELATIONSHIPS among the invariant features underlying a specific movement class of skill

BEFORE:

1. Initial conditions (What needs to happen)

2. Response specifications (parameters) (Numbers to put into the program)

AFTER

3. Sensory consequences

4. Response outcome

hate you

stupid question thing

Cognitive-based theory challenges

Context-conditioned Variability Problem

Degrees of Freedom Problem

Context-conditioned Variability Problem

Need to account for other forces acting on the body (inertia, reactive forces, gravity, centripetal forces)

Reactive forces

Ground pushing back and gravity pulling down

Degrees of Freedom Problem

All the different ways a system can independently vary = motor equivalence

Sufficient complexity to negate an exclusive role for cortical structures / motor programs

Picking most efficient movement patterns

Dynamical Systems Theory

A collection of interacting parts that functions as a single entity that is in motion or exhibits change over time

Uniform goal

Always changing, movement , etc

Muscle fibers example

Always interconnected to contract the heart together

Dynamical Systems Key Components

Complexity

Nonlinear dynamics

Attractor states

Phase shifts

Emergence

Self-organization

Complexity

Dynamical systems are comprised of diverse elements (Different components) that are connected and interdependent, and capable of adaptation

Many degrees of freedom are REQUIRED

Neccessary

Elements rely on each other, consider other components

Can adapt

Ex: All ants working together

Nonlinear dynamics

Behavioral change is NOT always a linear relationship - it is often abrupt

Threshold phenoma (stable and then big change to different state)

Motor changes

Ex: Transition from walking to running with speed increasing is critical threshold

Attractor States

Preferred behaviors or patterns = motor HABITS

Perturbances and Phase shifts

Drawn to attracted states

Fall into easy, HARD to get out of motor pattern

Shallow or deep attractor wells

Ex: Low energy motor habit sitting slouched

Perturbances

Something that triggers phase shift, getting out of habit

Phase shifts

One movement pattern to another

Perturbance

Change in circumstances such that the attractor state is no longer stable / comfortable / effective

New motor behavior often emerges

Ex: Changing gait pattern based on what's on your feet

Phase shift or "tipping point"

The spontaneous transition from one pattern to another - the system seeks stability or to meet specific goals

Typically, its a response to a perturbation

A result of self-organization

Take stress to critical point (tipping) to another movement pattern

Emergence

The spontaneous creation of a new state or movement pattern resulting from the self-organization of the elements of a complex system

Built in a specific way to do specific types of movements

Can have walking with no nervous system

Emergence with constraints

Limited to act within certain boundaries = constraints

Biological

Environmental

Task

Limits our bodies and what we can do

Environment

Source energy or barriers (Ex: Waves to surf)

Task

What are you trying to do

Emergence: Novel Environment

Low gravity environment with space and learning how to move

Self-organization

The tendency for elements within a complex system to synergistically adapt so that new states or patterns emerge

Individual components each adapt to changing circumstances in their own unique ways, contributing to the emergence of new patterns

Creating order from disorder

Adaptive

Changing in response to the environment

Each component open to environment

Openness

Seeks information from its environment and makes that information widely available to the system (Behavior transmits information to the rest of the system)

Externally focused (More focus on group or environment)

Self-reference

Responds in a way that is consistent with its own inherent guiding principles

Internally consistent (with the goals of the certain organism)

Dynamical Systems Summary

Human movement emerges as an interaction of many systems and subsystems (biological and ecological) which are both connected ,interdependent, and adapting.

Synergies represent self-organization (spontaneously organizing into cooperating collectives)

Dynamical Systems applications for motor learning key concepts

Limit degrees of freedom early (Fewer things for learner to manage)

Clustering into synergies

Practice = exploration and exploitation

Similar instructional implications as the schema theory

Learners need opportunities for self-discovery

Degrees of Freedom

Learning and improving skills =having more degrees of freedom available but fewer they must directly control

Spontaneous movement in long run

Freeze Out

Less degrees of freedom so there is less to cognitively control (Lock up / co-contract)

Over time, they begin to relax / incorporate some muscles for more joints to move more freely

Momentum, transmit energy, etc

Synergies

Clustering these degrees of freedom into cooperating collectives

With practice, movement elements that are specific to a given task become temporarily linked for the purpose of task execution

Practice : Discovery Learning

Learning is a balance between exploration and exploitation of the performance landscape

Practice design is an attempt to create the most beneficial context in which the most effective movement patterns can emerge

Variable Practice

Similar instructional implications as the schema theory: variable practice

Providing safe opportunities for self-discovery

Rock climbing, fair activities, etc