Motor Control Theory Chapter 5 – slide set 4 The crucial relationship is: From the last slide...
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Motor Control Theory Chapter 5 – slide set 4
Motor Control Theory Chapter 5 – slide set 4 The crucial relationship is: From the last slide set… Between the order parameter(s), control parameter(s)
The crucial relationship is: From the last slide set Between
the order parameter(s), control parameter(s) and stability For the
baby stepping: Order parameter = step reflex; control parameters =
fat weight, muscle strength, environment Energy efficiency is the
overall guide to the circumstances under which the step is more or
less stable
Slide 4
The crucial relationship is: So where does the step part of the
movement come from? Remember the idea of interacting parts of a
system (from the water example)? Here the interacting parts are
muscles, and their connections When innervated as a whole, the
babies muscles resolve themselves into a kick
Slide 5
The crucial relationship is: and the dynamics of the CNS
adapting to the most energy efficient solution to the problem
(given enough time and experience) Leads to many local solutions
Learning progresses by de-stabilizing these in favor of more
effective solutions Think of developing bad habits in sport, and
trying to get out of them the longer they have persisted, the more
stable they are and the harder they are to break
Slide 6
Relating to humans another example running and walking (see
link below) 1.Order Parameter 2.Control parameter 3.Attractor state
A C B
http://perso.wanadoo.fr/l.d.v.dujardin/ct/cusp.html#applet2
Slide 7
But really how does it apply to humans??? Another example:
Kelso & Scholtz, 1985 In-phase: Faster and faster
Slide 8
But really how does it apply to humans??? Another example:
Kelso & Scholtz, 1985 In-phase: Faster and faster Kelso &
Scholtz, 1985
Slide 9
But really how does it apply to humans??? Another example:
Kelso & Scholtz, 1985 Anti-phase: Faster and faster Kelso &
Scholtz, 1985
Slide 10
But really how does it apply to humans??? Another example:
Kelso & Scholtz, 1985 Anti-phase: Faster and faster Kelso &
Scholtz, 1985
Slide 11
But really how does it apply to humans??? Difference between
jt. Angles CoordinationStability Variation in jt. Angles (arbitrary
units) Stability and attractors The in-phase and out-of- phase
states in the Kelso example are attractor states for the movement
Perturbing the movement when it is in a stable attractor region
will result in a quick return to stability (in- phase)
Slide 12
But really how does it apply to humans??? Stability and
attractors Perturbing the movement when it is close to a region of
instability will result in either a longer period of instability
followed by a resumption of the original state, or a new attractor
state When close to a period of transition, the movement will
exhibit critical fluctuations the movement will be more wobbly,
less stable Difference between jt. Angles CoordinationStability
Variation in jt. Angles (arbitrary units)
Slide 13
Exploring the coordination of movement using synergetics 1.
Define system and joint motions used to perform task 2. Scale a
parameter within the task and identify the slowest moving
relationships of joint motions (order parameter) 3. Scan the
dynamics of the slow moving relationships 4. Identify the preferred
and non-preferred patterns 5. Choose a potential control parameter
6. Determine the relative stability of the patterns within a phase
transition experiment 7. Mathematically model your system 8. Test
the model
Slide 14
Properties of DST Attractor states are characterized by optimal
energy efficiency Stability Self-organization Motor development
example: The emergence of the shape of the step wasnt dictated by
the brain, but emerged as a consequence of the interplay amongst a
whole range of variables.
Slide 15
Properties of DST Coordinative structures Partial solution to
the degrees of freedom problem joint or limb components linked to
each other during movement become sensitive to the movements of
other parts they become one structure for the purposes of
coordination Kelso et al. (1984) jaw movements Arytunyen et al.
(1980) pistol shooting
Slide 16
Properties of DST Perception-action coupling Rather than the
brain specifying behavior, the environment specifies behavior (such
as timing) that is it constrains the movement in an important way
There are many examples of this: Long-jump (Lee, Lishman &
Thomson, 1982) Control of braking (Lee, 1976) Catching
(Savelsburgh, Whiting & Bootsma, 1992)
Slide 17
Perception-action coupling - examples
Slide 18
Slide 19
Other thoughts... Embodied cognition in artificial
intelligence
Slide 20
Other thoughts... Pictures from Thelens (and Ulrichs) early
research stepping and kicking
Slide 21
Other thoughts... Pictures from Thelens (and Ulrichs) early
research walking on a treadmill
Slide 22
Other thoughts... Data from Thelen et al. 1993: two children
showing very different approaches to reaching for an object.
However...
Slide 23
...by the end of the first year, the movements are very
similar. What does that say about the search for coordination
?
Slide 24
Other thoughts... Schematic from Thelen et al. 2001: the A not
B problem. A truly complex and adaptive case of modeling order and
control parameters...see next slide
Slide 25
Other thoughts... Excerpt from Spencer et al (2006): the A not
B problem. A list of control parameters in the task. And another
comment on embodied cognition. DST doesn't only deal with
movement.