Alternative motor control theories 2

Question 1

Describe the Lorenz strange attractor:

Answer 1

• When he put the same number into a mechanical calculator, he did not get the same answer
• Pattern that stay constraint to the same shape, but has a different value each time
• Random noise or a complex system
  Strange attractors are very sensitive to initial systems - gets very different variations of the same pattern, attractor taking you to the same pattern, do have structure

Question 2

Can we get complex “control” from:
- mechanics and some simple control structures?
– given time and simple rules from simple control?

Answer 2

• yes
• Yes depending on how complex we want to be

Question 3

What is the Mandelbrot set formula?

Answer 3

iterate Z = Z^2 + c

Question 4

Describe the cobweb of chaos:

Answer 4

When there is a huge number of possible solutions, diagram become very complicated
- Simple interaction that becomes very difficult very quickly
- Increase in stable solutions, which then collapses, then increases again
- This is chaos not randomness, as clear patterns evolve

Question 5

Why don’t mean, SD tell the whole story?

Answer 5

Need measures which take into account how the signal changes or develops over time. Signal Complexity Information Content
- Mean and SD can stay practically the same, but diagram changes greatly

Question 6

What are some techniques to measure time series data?

Answer 6

• Approximate entropy (ApEn)
  – quantify the amount of regularity and the unpredictability of fluctuations in time-series data. Information content.
• Detrended fluctuation analysis (DFA)
  – determine the statistical self-affinity of a signal, analysing time series with long-memory processes, looks similar over a long period of time
• Lyapunov Exponent (λ, lambda)
  – characterizes the rate of separation of infinitesimally close trajectories, as in Lorenz attractor, tells you how far things diverge from each other

Question 7

What are some variabilities in human movement?

Answer 7

– End effecter Vs intermediate limbs
– Intra stride running changes
– Bimanual coordination
– Skill breakdown and coordination
* Heart rate
* Concussion - brain patterns are most linearly shown during a seizure