Dynamics of Bernstein’s Level of Synergies Presentation by Susan & Joaquin.

Dynamics of Bernstein’s Level of Synergies

Presentation by

Susan & Joaquin

Readiness

• Take out a piece of paper• Draw a picture depicting one of

the five challenges to the level of synergies

• Underneath your picture, define the level of synergies and explain how your picture depicts a challenge to the level of synergies

Class Objectives

• Explain the benefits and drawbacks of the level of synergies

• Identify all five challenges for the level of synergies, and provide specific examples for at least three of them

• Explain the importance of rhythm to the level of synergies

What is the Level of Synergies?

• Level B, known as the level of muscular-articular links

• Why important? – No other level able to control large-scale

movements (running/jumping/swimming)– Able to produce rhythmic movements,

leading to cycles and automation (minted coins)

• Downsides?– Needs help from other levels C and D to

function in environment

Review of Levels

Level

Purpose Example

D Changes in environment

Walking backwards while tossing a ball back and forth

C Accuracy Walking in a line, heel to toe

B Rhythmic movements

Walking

A Muscle tone Helps maintain spinal column

Five Challenges For The

Level of Synergies

Challenge 1

• How to select the pattern of agonist and antagonist muscles that will produce a given movement trajectory

• Movement of any limb requires the use of 2 muscles from that region

–Work as agonists or antagonists depending on angle–Agonist = together–Antagonist = away

• Example: arm wrestling

Challenge 2• How to bring about muscular synchronization in

which different muscles must contract by different amounts in equal time

• Reaching for somethingrequires a linear angle, the hand moves in a straight line• Straight-line movements decrease directional changes which may cause a loss of balance

• Force must be applied to move an object from one specific point to another. This is done simpler if paths are straight lines because they will create smoother movements.

• 2 different techniques:

Asynchronous Synchronous2 muscles start to contract together and continue together until the task has been completed

2 muscles start contracting together but they contract at different times and the muscles stop contracting at the same time

Train tracks Making a “U-turn”

Challenge 3• How to bring about segmental

synchronization, so that limbs and limb segments with different frequency preferences move at the same frequency

•There is a competition between limbs•Arms and legs have different weights, and if

detached would swing at different speeds•A compromise must be made for success

Challenge 4

• How to separate timing from power, pattern from energy

• Mvmt demands will determine level of synergies

• 4 legged animals (cats, dogs, horses) have ability to walk, trot, or gallop either at low/high speeds

• For each movement, the 4 limbs must pass through their respective cycles in sequential time.

• The movements of the limbs and limb parts cannot move all at once and therefore need to be told by the brain centers when and how to move a particular limb

Challenge 5

• How to make the component degrees of freedom correct themselves to ensure pattern retention

• Synergy must be self-organizing system• Must have a mutual understanding of how

to take care of its own degrees of freedom• Must be able to correct itself when its

pattern is interrupted

Nearly Decomposable Systems

• The exchange of actions within a subsystem are usually heavy, but the exchange of actions between subsystems tend to be light.

• Subsystems tend to work independently of each other

• Primarily, the high-frequency behavior of a subsystem is independent of the high-frequency behavior of other subsystems

• Secondly, the behavior of a certain subsystem relies on the actions of other subsystems with which it comes in contact with.

Rhythm

• Successful cycles of a repeated act are like “minted coins”

• Bernstein gives 5 reasons rhythm is compelling

1. Are ubiquitous in living systems2. Explains how the nervous system organized

movements and resolves efficiency of motion3. Obeys simple rules, yet parts involved are

complex4. Evolve with different levels of variation5. Oscillations (fluctuations) are dynamic

Von Holst’s Fish

• Fish swim by fin movements, body is still

–Absolute coordination: fins move @ same frequency–No coordination: Each fin moves @ own frequency-Relative coordination: Fins constant, then wander, then return to mutual attraction and frequency

Fish Experiment

• Von Holst surgically cuts fish to control the nervous system

He discovers the components of a synergy :

(A) Compete (the maintenance tendency)(B) Combine (superimposition)(C) Cooperate (the magnet effect)

(A) In absolute coordination, the maintenance tendency states that if one fin were to be interrupted, the other fin would continue with it’s normal cycle.– Therefore, the fins of a fish are always competing

with each other.

(B) In relative coordination, superimposition is present when numerous rhythmic synergies are active which causes the behavior of a synergy to be dependent of others

–automatic adjustments are made among other subsystems comprised of any large-scale synergy–produce more detailed rhythmic synergies by combining simple rhythmic synergies

• (C)The magnet effect determines and maintains the frequency and phase relations among components.– As two fins beating with different frequencies and

with different amplitudes, frequencies united, but amplitudes remained unchanged

Contribution to Dexterity

• Bernstein says dexterity requires minimum of two levels of the movement hierarchy

• Leading level: switches among patterns and adjusts as needed

• Background level: contributes harmony, precision and obedience

• Example: Rider (leader): quick-wittedHorse (background): obedient

• Skills involve the level of actions (D) as the leading role, and the level of synergies (B) as the background role

• Rider: has definite goals in mind and clearly identified paths to travel

• Horse:has other constraints that must be satisfied

• Success = satisfying constraints for the horse

End of Presentation

5 Challenges1. How to select the pattern of agonist and antagonist

muscles that will produce a given movement trajectory

2. How to bring about muscular synchronization in which different muscles must contract by different amounts in equal time

3. How to bring about segmental synchronization, so that limbs and limb segments with different frequency preferences move at the same frequency

4. How to separate timing from power, pattern from energy

5. How to make the component degrees of freedom correct themselves to ensure pattern retention

Review of Objectives

• Explain the benefits and drawbacks of the level of synergies

• Identify all five challenges for the level of synergies, and provide specific examples for at least three of them

• Explain the importance of rhythm to the level of synergies