Lecture #6: Theories and Problems

Question 1

What are the two theories of motor control?

Answer 1

1. Motor program based theory
2. Dynamical systems theory

Question 2

Motor program based theory

Answer 2

Cognitive based mechanism that controls coordinated movement.

Question 3

Dynamical systems theory

Answer 3

1. Role of info in environment and mechanical properties of the body and limbs in movement control/coordination.

Question 4

Generalized motor program (GMP)

Answer 4

1. Hypothesized memory based mechanism responsible for adaptive and flexible qualities of human movement.

Question 5

What does the GMP do?

Answer 5

1. Controls a class of actions, which are identified by common invariant characteristics.
2. To serve as the basis for generating movement instructions to and during performance of an action.

Question 6

Who came up with the GMP?

Answer 6

1. Richard Schmidt

Question 7

What are the two features of the GMP?

Answer 7

1. Invariant features
2. Parameters

Question 8

Invariant features

Answer 8

1. Characteristics do not vary across performance
2. Identifying signature of GMP

Question 9

Parameter

Answer 9

1. Specific movement features that adapt to situations.
2. Can vary from performance to performance.
3. Ex. Overall amount of time taken to perform a skill

Question 10

Relative time

Answer 10

1. % of total amount of time required by each skill

Question 11

Schema Theory by Schmidt

Answer 11

1. Set of rules that serves to provide the basis for a decision.
2. Ex. Correctly identifying an animal that you have never seen before as a dog.

Question 12

First Control Component (GMP)

Answer 12

1. control movement coordination
2. Provides invarient features

Question 13

Second control component

Answer 13

1. Motor response schema (provides specific rules governing the performance of a skill.
2. Provides parameters

Question 14

Dynamical Systems Theory (DST)

Answer 14

1. Describes control of coordination movement by emphasizing the role of environment info and dynamic properties of body/limbs.
2. 1800’s influence
3. View human motor controls as complex systems that behaves like any complex bio or phys system.

Question 15

Who worked with DST?

Answer 15

Nickoli Bernstein

Question 16

Two problems associated with cognitive based theories?

Answer 16

1. Context conditioned variability problem
2. Degrees of freedom

Question 17

Cognitive based theories: (CCVP)

Answer 17

1. Specific movement outcomes are dependent on specific commands found on motor program.
2. What if the context in which the movement is produced changes?
3. Will same commands result in same outcome?
4. Adding weight when doing adduction vs moving arm fast. (same outcome with same movement?)

Question 18

Degrees of freedom

Answer 18

1. How many planes and axis alter when you move(number of ways in which a system can independently vary)
2. How control a system of many moving parts?
3. Same goal can be achieved by different movements (hitting a hammer over and over.)

Question 19

Solutions to the problems: Synergies

Answer 19

1. Different actions being arranged in such a way that it achieves a goal of some sort. (very task specific)
2. Arrangement of joints and muscles in clusters to control our movements.
3. Freezing the degrees of freedom: Limiting the movement of limbs and joints (refining over time)

Question 20

Coordinative Structures (muscle Synergies)

Answer 20

1. Groups of muscles (joints) constrained to act as functional units
2. Walking with a a leg in a cast.
3. Swinging a golf club (multiple muscles working together)
4. Developed through practice and experience.

Question 21

What is dynamical systems theory based on?

Answer 21

1. Non-linear dynamics: Behavioral changes are not always continuous, linear progressions still present but are often sudden or abrupt.
2. Ex. Boiling point of water
3. Behaviors self organize in response to constraints.

Question 22

Order Parameter

Answer 22

1. Order parameter (collective variables)
2. Overall behavior of the system
3. Enable a coordinated pattern of movement to be distinguished from other patterns.
   -Relative phase is the most prominent order parameter: Show how one joint segment moves relative to another.

Question 23

Control Parameter

Answer 23

1. A variable, when increased or decreased, will influence the stability and character of the order parameter (Ex. Speed)
2. Important to identify since it becomes the variable to manipulate in order to assess the stability of order parameter.
3. Provides basis for determining attractor states for patterns of limb movement.

Question 24

Self Organization

Answer 24

1. Emergence of patterns of behavior due to the conditions of the environment.

Question 25

Examples of Self Organization 1 (Gait Transition)

Answer 25

1. Person walks on treadmill at slow speed. 2. Treadmill speed (Control parameter) increases. 3. Person shifts to running at a certain speed (not same speed for all people) 4. Same effect if person begins running on treadmill-shifts to walk at certain speed.

Question 26

Examples of Self Organization 2 (Swim stroke transitions)

Answer 26

1. Each trial involved a swim velocity increase (Began at preferred velocity) 2. Arm-stroke analysis showed 2 distinct patterns of arm coordination. 3. Began in one mode but abruptly began 2nd mode at a specific swim velocity.

Question 27

Attractor

Answer 27

1. Stable state of the motor control system that represents preferred patterns of coordination (ex. Walking)

Question 28

What are the characteristics of an attractor?

Answer 28

1. Identified by order parameters (ex. Relative phase) 2. Control parameters (speed) influence order parameters. 3. Minimum trial to trial performance variability 4. Stability: Retains present state despite perturbation 5. Energy efficient

Question 29

Why do we see an increase in energy expenditure when going from walking to running?

Answer 29

1. Because our body is trying to decide what system to use that change in the system to another attractor state to stabilize the system to maintain energy deficiency.

Question 30

Constraints (on performance)

Answer 30

1. Boundaries that limit possible values or patterns that a system can assume that are imposed by the organism, physical environment, and task itself.

Question 31

Organismic Constraint (Ester Thelen)

Answer 31

1. Characteristics of the individual, including both structural and functional characteristics. 2. Infants with stepping behavior goes away after a few month's. Why did stepping behavior go away? They got too fat.

Question 32

Environmental Constraint

Answer 32

1. Walking on an uneven path with affect walking (performance) 2. Arise in both the physical and the sociocultural environments of individuals

Question 33

Task Constraints

Answer 33

1. Constraints on human movement imposed by the task performed, including task goals, equipment used and mandated rules and protocols.