The feedback problems you are talking about, when applied to brains, walks
into philosophy pretty fast. I am going to try and avoid philosophy.
1. In some systems there is no controller. The entire basis of all entities,
and subsystems, in these systems, is feedback and codependency on the their
environment. Examples of this are ecosystems. Owls don't control rodents,
kill (knockout) all the rodents, and it will appear to some like the owls
depended on the mice to tell them how to get food (psst bird, go kill marky
mole, he is hiding under that mushroom over there, he stole my seeds). We
have an advanced knowledge on this ecosystem so we know this is not true,
however with random extermination (knockouts), abstract and removed results
can occur. Using the simple ecosystem with a different removed effect,
(pesticide) effect on Falcons. The p.falcons were wiped out in some areas due
to the use of a pesticide. The effect was the same "knocking out the rodents"
but in this case it wasn't something the birds ate that was being removed.
The birds weren't being effected by pesticide spraying either. The falcons
were killed by the way the new "factor" in the falcon's environment moved
through the environment (pesticide was concentrating through the food chain).
All things can appear to be directly correlated in a poorly understood system.
(or even a well understood, but complex, system) (Other examples abound...)
Often no conclusion can and should be drawn from observations. (statements
can be made about cause and effect, state and status, but that is about it..)
> finding sources of control in the brain. Part of this note is to clarify a
> confusion in these fields about interacting modules in a system and on the
> question of who controls whom in these systems. The second part of the note
> raises various questions about how to determine which part of the system is
> actually the controller of the system.
>
> A) On who controls whom in an interacting system?
>
> On the conjecture that there are parts of the brain that control other
> parts....
It sounds like we are seeking the super brain. The brain which controls the
brain? (I am asking) Would we accept a complex feedback processing center as
a controller even if it was heavily or completely dependent on feedback from
its environment or another subsystem, of which it had little or no direct
control over? To take it even farther, what if our super brain was actually
being controlled by another subsystem, but in a vary menial manner, would that
disqualify it as the super controller?
Somethings will always have half truths. The idea of controlling controllers
when feed back is involved, is analogous to the heap of sand, and when does it
cease to be a heap, if you are slowly removing grains? When does one heap
become more of heap than another heap when the heaps are of the same size, but
of shifting shapes?
I will suggest we can map the relationships, but as to mapping our traditional
hierarchical system designs onto it, I am very skeptical of any definitive, or
unarguably conclusive results.
> By engineering definition, a control system consists of a "master or
> controlling subsystem" where the "control" signals are generated, and a
> "subservient subsystem" where these control signals are used. In a simple
> feedback control mechanism, the output of the subservient subsystem is
> fedback to the controlling subsystem. So although the overall system can be
> seen as interacting subsystems, we call one subsystem the "controller"
> because of the "nature or role" of its signals. The fact that the signals
> from the controller are based on or influenced by signals from other
> subsystems does not change the "nature or role" of these signals that we
> call "controlling." So blood is perhaps not the "controller" of the system,
> although the system does not work without blood. Analogy: electrical systems.
I was trying to show above, some systems are not control systems. The brain,
although appearing to be a control system, could quite easily not be a control
system. We have merely switched from the the blood, to the heart, to the
brain. (the old history thing again, we are looking for what we can't find,
in the next most complex spot we can't understand completely, but can
identify) (another bad "knockout" example: bleeding makes people feel better,
and helps cure illness. (bad blood))
> B) Who is a controller and how do we detect it in an unknown system?
>
A question which I think should precipitate this would be: How do we determine
if an unknown system has a controller. (take me to your leader)
> ... . It is perhaps now an accepted fact
> that the brain controls the rest of the body.
agreed.
> C) On the test for a controller in any system
> So a possible means of testing for a
> controller in an overall system might be to isolate each subsystem and
> observe the behavior of the resulting system. If the resulting system is
> still a functioning system, although briefly perhaps, then the isolated
> subsystem might be the source of control in the system.
I understand, but cannot think of any examples of where this would work in a
complex system. If you have any positive results on this please let me know.
>
> I think this test can be applied very well to any man-made system to
> determine the controlling subsystem in a system. My question is, are these
> ideas applicable to natural systems as well? If not, why not? What are the
> flaws in this idea? For example, using this test mechanism, it is easy to
> determine why the heart or the liver or the lungs do not qualify as
> controllers of the system. But a brain-dead person or one in a coma is still
> a functioning system, with some severe limitations of course. Does that
> qualify the brain as the controller of the system?
>
Natural systems are inherently interdependent. (otherwise they wouldn't be the
way they are) This is what is causing us all the grief. I don't think we have
advanced far enough to be able to classify levels of control properly in
complex systems. (good topic for a thesis here) Analyzing and mapping a
complex systems so they can be broken down like plumbing would truly be nice,
but still out of our reach for the time being.
>
> My question is, can a test idea like this be used to determine that there
> are parts of the brain that control other parts? I quote here from a very
> interesting response
A combination of approaches combined would be more suitable, with your
approach being a possible member of the combination. I would abandon the hope
of finding a single test which would yield success.
> mouse knockout testing
> It appears that the "test of a controller" framework outlined above is being
> used in this study. My questions again are: First, can this test mechanism
> for a controller be used on natural systems too? Second, does the above
> study point to sources of control in the brain?
I would argue testing methods mentioned are inconclusive for the reasons I
mentioned above. I believe they are suitable only for pharmaceutical purposes
at this time. (lithium anyone)
If massive amounts of tests were to be applied (of all varieties, not just
knockout), and the results mapped, I believe the mapped results could be
examined to find the sources of control, if there are any present. As to what
tests ... I suggest a list be started, with the caveat that the results of any
one test are not to be taken in isolation.
Isolation
Knockout
Stimuli (above the normal feedback)
manual feedback adjustment
normal feedback
Cheers
David Murchie
BC, Cascadia
(feel free to post this to the list)
PS The quest for identifiable controllers reminds me of proverbial quests for
the meaning of life, god, and purpose.
Below is a clip from a something I wrote before, It seems relevant.
The brain is reactionary. It achieves the states is does via reaction with
its surroundings. The brain is dependent on the body for survival
(nutrient/energy), but can function with independent failure, or bypassing of
any other part of the body. The brain can function independent of the other
parts of the body, but not usually in a desirable way if the brain is cut off
from too much external stimuli. (i.e. external stimuli control / determine
brain function, external stimuli gets encoded in brain. External stimuli
manifests through brain as behavior, attitude, stress level, diet etc. I
realize this appears to be a drastic example of our brain being no more than a
complex encoder. The brain has basic rule sets built in which guide behaviour
(aka instinct). The brain will function in a basic manner without the
external controlling stimuli, but not in a reasonable manner. (deaf, dumb, and
blind infants don't do so well, they require external input to control how
they develop)