From [ Marc Abrams (2003.07.03.0039) ]
> [From Rick Marken (2003.07.02.2000)]
> If you don't have B:CP a paperback version should be available soon.
If it does I would strongly recommend that he re-write this part of the
book. It's showing it's age.
> I'll answer that question the way you answer my questions: by pointing you
to a
> book, but in this case a book that I presume you have on hand, _Behavior:
The
> control of perception _ (B:CP) by William T. Powers.
Got it right here.
>Your first question is answered on p. 83, in Figure 7.1. Actually, the loop
shown there goes through
> the spinal cord, not the brain, but as you will see, it works the same in
the brain (cortex, cerebellum, etc).
Sure, brain, spinal column, liver, kidney, what difference does it make, you
know what he's talking about.
> The Figure shows that the perceptual signal in this is carried by sensory
nerve impulses.
"THE" perceptual signal? One perception = one signal?, Do you actually mean
_one_ signal? What are 'nerve impulses'? Is that the oscillation of the
interneurons or neurons?
What happened to the chemical ions in the neurons? Do they play a part in
synaptic actions and neuronal communication? Exactly where in B:CP should I
find these answers?
> The reference signal is carried by efferent nerve impulse,
Did you know that many neurons are _bi-directional_? How do you know the
'reference signal' ( again, only one signal? ) is efferent? I know, Bill
told you so in B:CP. Seems reasonable. Where does this 'reference' signal
come from? Don't tell me from the level above. Again you do not mention the
chemical component in intercellular communication. Where do you think the
'electrical impulses' come from?
>the reference efferent neurons in this case descending down the spinal
cord.
Where did they originate? These of course being 'motor neurons' right?
> The comparison itself is done by the cell body of a spinal motor neuron
(which I believe makes up the motor ganglia next to the spinal cord).
A ganglia is nothing more then a cyst. What is a 'motor ganglia'. There is a
part of the brain known as the basal ganglion, and in the visual cortex
there are ganglion cells, but I never heard of a 'motor ganglia'. The cell
body does nothing. The cell is a highly specialized and compartmentalized
entity and the cell body simply holds the parts of the cell. The only way
that cells speak to each other is through ionic channels. Most neurons do
act independently. They 'act' in 'patterns'. Might I suggest _I of the
Vortex_ by Rodolfo Linas 2001 MIT Press. Dr. Llinas is the Chairman of the
Physiology and Neuroscience Department at NYU's Medical School here in NYC.
Either that or look for the Cliff notes in your nearest book store.
>The comparison (an approximate subtraction) is the result of the
simultaneous inhibitory effects of the sensory synapse and excitatory
effects of
> the efferent synapse on the firing rate of the spinal motor neuron itself,
Huh? You mean _all_ sensory inputs are 'inhibitory' and _all_ motor outpouts
are 'excitatory'? How can a synapse be efferent? A synapse is nothing more
then a cleft between two neurons. And finally, what is a 'firing rate'? What
gets 'fired' from one cell to another? This is real bad. Not only is it
totally wrong, but it makes the rest of the model, which has some
_excellent_ properties, look like ^%#&^%.
>which carries the error signal as neural impulses. This error signal enters
the environment, a muscle, at the motor end plates, causing the muscle to >
contract in proportion to the rate of firing of the spinal motor neuron.
On and on you go. What the hell is an 'error' signal? Is it a special type
of coded transmission between cells? How would you know an 'error' signal
from a 'reference' signal?
>The degree of muscle tension (which also depends on any loads on the limb
to which the muscle is attached) is sensed by
> the Golgi tendon receptor (in the tendon that connects muscle to bone) .
How does the receptor 'sense' the weight?
> Tension on the Golgi receptor causes neural firing in the sensory nerve,
the
> rate of firing being a perceptual representation of the tension on the
tendon.
This sounds 'wonderful'. Where is the feedback and control? I just see
motor output. What if the receptor 'senses' wrong? How does the 'Golgi
Receptor' adjust?
> A more thorough picture of the parts of the brain and spinal cord that are
> thought to be involved in three lower levels of the hierarchy is shown on
p.
> 117, Figure 9.1.
Very nice, but not quite accurate.
> The first order control systems are in the spinal cord, the second order
systems are in the cerebellum and the third order systems are in
> the cerebellar cortex.
Says who? Outdated, and old ideas about the brain had it divided
'functionally', that is, certain parts of the brain performed certain
functions. The cerebellum was thought to be involved with our motor (
muscle ) skills. It has been learned that the pure 'functional' view of the
brain is not accurate. Lots of things happen in all parts of the brain. Yes,
certain parts of the brain seem to have more of one type of activity then
another, but things pretty much get spread around. In one recent experiment,
they found that blind people were utilizing there 'visual cortex' area (
that's in the back of the brain ) for verbal memory. The pure functional
model, although still adhered to by some, is out of fashion. Of course this
is all very sophisticated hand waving. But I'd venture to say that these
people have a lot more to work with then Bill had 50 years ago. Brain
research has come a long way in the past 5-10 years, and it's getting better
and better.
> If you don't have B:CP a paperback version should be available soon.
I think I'll wait for the movie.
Marc