neurotransmitter storage (all or one?)

Richard Norman rsnorman at mediaone.net
Fri Sep 1 16:09:27 EST 2000


I am afraid your postscript says it all

    "For those who believe,
    no explanation is necessary.
    For those who do not,
    none will suffice."

The most interesting thing about physiological systems is how variable
they are.  You generally can NOT replicate exactly a situation which is
determined by a large number of parameters.  But that is a simple fact
of life.  And by having a large number of molecular events, like ion
channels,
all responding to the same situation, you do get a significant degree of
"precision" or repeatability in the response.  It is true that the action
potential is one mechanism that cells have of reducing the variability.

But anyone who has actually looked at action potentials recorded from real
cells knows that they are not all identical -- some are larger some smaller,
-- some have faster rise and fall times, some slower -- some have longer
duration, some shorter.  And these variations are found between cells and
within one cell from moment to moment depending on the history of activity
and on signals delivered from adjacent cells, not to mention the glial
activity.  And these variations do have important consequences in
information
processing in that they significantly influence the amount of synaptic
transmitter released.

You reiterate "I have been trying to put the idea across
that a neuron cannot process information in an analogue manner
USING graded responses. This is because of the randomness
produced during each graded  response cannot be replicated
when needed"

The fact is that real neurons in real nervous systems DO process
information in an analog manner using graded responses.  Like it
or not, that is how the cells work.

"Theophilus Samuels" <theophilus.samuels at btinternet.com> wrote in message
news:8oorj9$8im$1 at plutonium.btinternet.com...
> I feel that you do not understand the real problem at hand. I am now going
> to
> try my best to explain it to you and hopefully you'll then understand.
>
> You wrote
> > Your argument from the beginning seem predicated on your thinking that
> > a digital system is well-defined whereas an analogue system is 'random'
>
> Now read carefully what follows. I am tired of giving examples for
> how
> to make a neuron analogue (see earlier postings) - can you think of one?
No
> one
> has yet given a suitable candidate(s). Remember, the states of the
> continuously variable
> quantity that you choose should be easily reproducible - for example, if
you
> choose the total number of ions taking part in a graded response, which in
> turn
> produces a 'specific state' in the neuron, then do you honestly believe
that
> the exact
> same number of ions can take part in a future graded response to produce
the
> same 'specific state' when called for? [See my last posting on the
workings
> of an
> analogue system, the snipped parts].
>
> The important thing to remember is that a neuron is unbelievably dynamic
> with
> respect to ion concentration, membrane permeability, protein synthesis,
> protein
> transport etc. So much so, that one state at a single point in time may
> never be
> reproduced in its remaining lifetime! In conclusion, how can information
> processing in the conscious human brain rely on a system that most likely,
> produces unique conditions that exist only once, momentarily in time?
>
> Going back to your quote, it is blatently obvious that you have no idea
> about
> the suggestions that I have been making, if this is my fault then excuse
me.
> When I am talking about a digital system and that the input/output
mechanism
> is
> well-defined, I am talking about AP generation. Anybody knows that an AP
is
> an
> all-or-nothing response - it either happens or it doesn't - to quote once
> more 'there
> is no messing around'. In this sense, a neuron has the means to create a
> well-defined communication network, so that the AP are generated when
needed
> for
> cross-talk and information processing. I think we need to get away from
the
> idea
> that a single neuron can process information on its own, instead we should
> now
> begin to focus on neuronal networks within the brain, whether they are
small
> or
> large. At this level, the well-defined level with respect to AP, a
coherency
> is
> observed that can never be seen in an analogue neuron. And yes, AP
> generation is
> in binary form, but what is the main difference between this binary state
> and
> that found in computers? Time, of course - the frequency coding concept,
the
> way these ON and OFF events are able to be produced in trains of action
> potentials with differing time intervals between each AP. And remember,
the
> information contained within these 'constructs' could equally be found,
not
> only
> in the AP itself, but also in the time between AP, i.e. both ON and OFF
> events.
> You can now see that the amount of information that can be contained
within
> a
> system like this is almost limitless, but unlike an analogue neuron,
easily
> reproducible when needed. The problem we as scientists face, is the
> inability to intrepret
> these signals - indeed, we are still unable to track these constructs in
the
> smallest neuronal network in situ, let alone be able to understand them.
> There is never any discrepancy, either the
> neuron produces the AP or it doesn't, and therein lies the key to how this
> system works, a neuron does not generate an AP but waits until it's forced
> to or
> has to (how this is achieved is a big mystery - I don't mean the
> biophysics -
> but the actual reason behind its generation).
>
> Fortunately, evidence supporting information processing in this manner
> comes from the use of drugs. In depression, or other neuro
> conditions, drugs act to suppress or disrupt AP generation by many
different
> molecular
> mechanisms. Susan Greenfield gives a vivid explanation in her latest book,
> about
> how these drugs suppress neuronal communication, and thus influence the
> emotional and/or conscious state of the individual. Albeit, these drugs
may
> work
> on the molecular scale, but again, the argument I present suggests that no
> coherent pattern of graded responses could be reproduced when needed, and
in
> fact, the introduction of exogenous drugs that disrupt the molecular ebb
and
> flow would only increase the apparent randomness of the analogue neuron.
>
> The original argument way way back, was that the brain processed
information
> only in an analogue manner. This was then redefined to include binary
> processing
> on a larger scale, so that an analogue/binary system was developed.
However,
> by
> using my argument, I suggest that the brain was never a true analogue
system
> in
> the first place because no one has yet given a suitable candidate for the
> physical
> variable required for an analogue neuron. Instead, if you think about it,
> the
> variable that I have introduced is TIME, so in that case, my proposed
> continously variable physical quantity was the fourth dimension. Indeed,
> using this
> concept one could say the brain processes information in a
> psuedoanalogue-binary
> manner (is time physical? -hence pseudo). Whether this gives rise to the
> conscious human brain is always in
> question, nevertheless it removes the unimaginable complexity faced with
> when
> dealing with analogue neurons.
>
> T.L.S.
>
> For those who believe,
> no explanation is necessary.
> For those who do not,
> none will suffice.
>
>
> Richard Norman <rsnorman at mediaone.net> wrote in message
> news:Ecdr5.11798$_e4.468005 at typhoon.mw.mediaone.net...
> >
> > "Theophilus Samuels" <theophilus.samuels at btinternet.com> wrote in
message
> > news:8ojiam$3cq$1 at plutonium.btinternet.com...
> > >
> > >.....<snip a lot of stuff>   The key thing to
> > > remember here, is that the digitial input/output mechanism is a
> > well-defined
> > > operation - it either happens or it dosen't, there's no messing around
> [I
> > > will come back to this again later>
> > > .....<snip another lot of stuff > Now here
> > > lies the difference between the randomness of an analogue system based
> on
> > > graded responses (this was the original argument) and .... <snip a lot
> > more>
> >
> > Your argument from the beginning seems predicated on your thinking that
> > a digital system is well-defined whereas an analog system is "random".
> You
> > have included this type of statement now in several of your posts.
> >
> > This is non only non-sensical, it departs from everything we have
learned
> > about the universe in the history of science.  There is underlying
reason
> > why
> > a graded or analog system cannot be determinate.  The mathematics of
> > partial differential equations well describes a tremendous variety of
> > phenomena that are continuously variable in space and in time.  In my
> > mind, digital systems with probabilistic state transitions are far more
> > "random" than the clockwork machinery of the Newtonian universe.
> >
> >
> >
>
>







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