Fitch, Tuller, Turvey (1982)

Tuning of synergies via perception

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Focus Questions

1. Describe the use of the terms relational invariance and metrical change on pages 271-272.

2. Explain the piano roll metaphor.3. What is exproprioception?4. What is the important aspect of the use of time-to-contact information in,

for example, the timing of a baseball swing?5. Is time to contact information restricted to vision? Give an example of

data supporting your answer.6. The extensive discussion of the posture and transport systems'

interaction, and the continued modification of the region of reversibility, are reminiscent of the discussion of the super-fast movements discussed in last week's lecture. How so?

7. Are the posture and transport systems arranged in a heterarchical or hierarchical manner?

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Focus Questions

1. Describe the use of the terms relational invariance and metrical change on pages 271-272.

The relational invariance captures the proportionality of the synergy. It’s the order parameter

The metrical change captures the change in the absolute force or speed of contractions It’s the control parameter

E.g. Nashner (1977) and the change in activity at hip, knee, ankle (while proportion stays the same)

• The change in the metric is “tuning” the synergy.

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Focus Questions

2. Explain the piano roll metaphor. Light only allowed through the roll at certain points Force only permitted/accessed/used by the synergy at

certain points Eg. The Watt governor, the pendulum clock, walking (E3

regulation)

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Focus Questions

3. What is exproprioception? Layout of environment in relation to the observer Proprioception tells us about how our body parts move in

relation to each other Exproprioception tells us how our body parts move in

relation to the environment E.g. swinging room, long jump, gannets, catching balls, hitting

dropped balls, playing table tennis, driving, etc. etc… http://www.youtube.com/watch?v=NTVtmUJeInY

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Focus Questions

4. What is the important aspect of the use of time-to-contact information in, for example, the timing of a baseball swing?

Allows regulation of an overall organizational plan (duration of swing) by a changing environmental cue (speed of ball approach)

Same thing has been found in the forehand drive at table tennis, gannet diving, and a whole host of others

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Focus Questions

5. Is time to contact information restricted to vision? Give an example of data supporting your answer.

No Same findings for muscular reflexes (falling on hands) Same findings for different senses (startle response in tactile

receptors on the back, facial vision) Tends to argue that the senses all “talk the same language”

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Focus Questions

6. The extensive discussion of the posture and transport systems' interaction, and the continued modification of the region of reversibility, are reminiscent of the discussion of the super-fast movements discussed in last week's lecture. How so?

Both Turvey’s description in 1982 and Riley et al’s discussion of 2012 involve very large number of d of f

Both suggest that any tweak of organization is compensated for by the dynamic qualities of the overall synergy

Riley provides evidence that this supercedes the kind of organization possible of a top down controller

The moderation is so quick that it has to be controlled at the level of the synergy

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Focus Questions

7. Are the posture and transport systems arranged in a heterarchical or hierarchical manner?

No. Massive dynamic interrelation among parts

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Final note on synergies…

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Bernstein and Coordination

• Some principles Distributed construction of movements

Gradual contribution to movement construction by many subsystems

Indefiniteness of action plans Same df can be used for different purposes, different df can be

used for same purpose Unlikely that actual use of df is stored as action plans More likely to be the relation among many parts at the dynamical

level

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Bernstein and Coordination

• Some principles Local expediencies

Each subsystem only knows what is has to know, given its relation to other subsystems

Subsystems may relate to each other according to overall rules, but these are dynamical organizations in principle …this

Not this…

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Bernstein and Coordination

• Some principles Separation of activation and tuning

Activation of a coordinated state brings the dynamic relation among the parts to action

Changes to the coordinated state are brought about by “tuning”, via other related subsystems (such as feedback – see time to contact examples)

Executive ignorance Because of the relation among the subsystems being defined via

local knowledge and their dynamics, the means by which they achieve the goal is not known to the executive in detail

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Bernstein and Coordination

• Some principles Reduction of d of f by synergies

Groups of muscles spanning several joints can be constrained to act as though having only one d of f.

Spring model of control Spring like properties of muscles exploited to use equilibrium point

control Special purpose and task specific solutions capitalizing on

real world complexity Problems of coordination are not universal but are specific to the

real world in which the problems are solved Within that world are invariants and lawful regularities which

suggest, or afford, certain solutions.

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Bernstein and Coordination

• Some principles Complementation of the movement system by its

environmental context of constraint The properties of the biological system (body) and those of the

environment in which it is embedded are not to be understood on their own• Understanding how they relate simplifies the coordination problem.

They constrain each other to act only in certain ways Simultaneous organization of afferentation with efferentation

Principles of movement organization must pay equal attention to coordination through inflow as well as outflow. Through perception as well as action. As above, one will constrain the other. There is mutuality• Watt governor again

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Bernstein and Coordination

• These principles are now being investigated using two complementary approaches Physical biology

Nonlinear dissipative thermodynamics Physics of self-organizing, open, far from equilibrium systems (those that

are exchanging energy with systems around them) Ecological psychology

Perception is specific to information Information is specific to the environment and one’s movements Information is the specificity of the structured energy distributions

available to the perceptual system• For every property perceived there is a property of the structured energy

distribution to which the perceived property corresponds.• E.g time to contact again!

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Bernstein and Coordination

• These principles are now being investigated using two complementary approaches Goal is to use principles of energy use to understand how

dynamic relations among subsystems are regulated, or organized Phase relationships among body parts Preferred coordination states Dynamic interrelationships of body parts with scale independence And so on…

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Bernstein and Coordination

• Take away points Interrelationships among parts of the system are complex Lots of specialization at lower levels It is unlikely that the executive has much detailed

knowledge of the detailed working of these parts What then of instruction?

Words? Demonstrations? How should one coach?