motor programs

Tom Holroyd tomh at BAMBI.CCS.FAU.EDU
Sat Apr 30 15:25:40 EST 1994


>> such as in nest building or web spinning.  There need not be any program
>> for web spinning at all, merely a small set of other behaviors.
>
>Wouldn't all of the programs comprising the different subsets constitute a
>web spinning program?
>
>>  Spinning is just a natural consequence of the
>> interactions (couplings) between the various subsystems,
>
>Why isn't this a complex program made up of many simpler subprograms?

Because it's not a "program".  A program is a serially ordered list of
instructions.  There is no serially ordered list of instructions inside
the spider.  *Sometimes*, you can *describe* a behavior with a set of
formal instructions, like 'swing your right leg forward, shift your
center of mass forward, set your right foot down, etc..', or 'spin in
circles before you lay down', but the animal has not such set of instructions
stored anywhere directing the movements.

If I put a pan of fluid on the stove and switch on the heat, the fluid
will organize into convection rolls, and turbulent eddies (if the heat is
high enough).  There is no stored program telling the fluid how to organize.

The Belusov-Zhabotinsky chemical oscillator forms spiral waves, but there
is nothing in the chemicals that specifies what a spiral wave is.  It's
just a dish of chemicals, whose reactions happen to form travelling waves.

The action potential in a neuron is a travelling wave in an excitable
medium; it is not obeying instructions that say "take this information
from here to there."

A complex network of interacting neurons may produce rhythmic temporal
sequences, but a description like "the large burst of spikes from R30
is followed by slow spiking from R28 that synchopates with the spikes
from L28, etc." doesn't tell us anything.

And you can't break it down into subsystems, either, because if you take an
element out of the network the dynamics (and the pattern it produces)
changes.

Tom Holroyd
Center for Complex Systems and Brain Sciences		   The basis of
Florida Atlantic University, Boca Raton, FL 33431 USA	   stability is
tomh at bambi.ccs.fau.edu					   instability.




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