neurotransmitter storage (all or one?)

Richard Norman rsnorman at mediaone.net
Tue Aug 29 10:23:31 EST 2000


I believe you are getting hopelessly involved in levels of physics which
are totally irrelevant to the question at hand.

A digital computer, in fact, does not work on digital or quantal physics.
Instead, it uses quite traditional and old-fashioned electronic circuits
which depend on continuously variable parameters of voltage and
current.  The circuits are designed with positive feedback so that
in one case the voltage is pushed as far as it can go in one direction
and the current is maxed out.  In the other, the voltage is pushed as
far as it can in the other direction and the current is halted.  But all the
underlying components -- whether vacuum tubes or transistors or
integrated circuits or whatever embedded in a silicon chip -- all these
work on continuous voltages and currents.  Except for a few extreme
cases still in the research stage, no real computer relies on
quantal states of matter or string theory or superposition of wave
functions or whatever.  Yes, those theories are needed for us to
understand how a semiconductor junction works.  But the operation
of a semiconductor circuit can be understood in the same terms as
its vacuum-tube forebears.

Why is there such a great need to impute magical or mysterious
mechanisms to the nervous system?  It is just an enormously complex
interconnection of cells.  Cells, that work according to classical
biochemistry and biophysics.

"Theophilus Samuels" <theophilus.samuels at btinternet.com> wrote in message
news:8oe5vl$gir$1 at uranium.btinternet.com...
> > Why should graded or analog processes be any less knowable or
> understandable
> > than discrete or digital ones?
>
> It depends entirely on what level one believes the process of information
> takes place on. For instance, on the atomic level the Heisenberg
Uncertainty
> Principle comes into play, on the other hand, the molecular level produces
> variations dependent upon certain thermodynamic conditions. All of these
> environments will inevitibly create a randomness that will defy absolute
and
> precise mathematical relationships - just look at the problems superstring
> theorists are having with perturbation theory.
>
> > That doesn't mean that these things are incomprehensibly complex, only
> that
> > we use a real number, a continuously variable measure, to describe them.
>
> The world at such subatomic levels is quite bizarre, as I'm sure you
know -
> the simple idea of superposition is a good example. You see, the problem
> faced by saying that the brain processes information in an analogue manner
> is that this by definition, this depends on a continuously variable
> quantity. What is this? Is it the number of ions that participate in the
> graded responses or the total number of dendrites that are affected by the
> electric fields set up by such conditions? Where does the level of
> processing lie?? Of course, nobody as yet knows the answer (if this were
to
> be true) and I suspect it will be a very long time until we do.
>
> > So I just am not sure why the
> > absence of
> > digital states makes any difference in how we see or understand the
world
> > around us.
>
> I think by now, we all accept that digital states are present within the
> brain, just as analogue ones are. As pointed out before, inputs from the
> periphery can only travel to the brain in trains of action potentials (ON
> and OFF events) and somehow these must be intrepreted - processed - in
some
> manner unknown to us all. Also remember, that the OFF states may just be
as
> equally important as ON states. For example, the absence of AP could also
> contribute to the final level of processing - as the composer Webern said
> 'the rests are just as important as the notes'.
>
>  To conclude, the brain may not just process information by either
analogue
> or binary means, but in fact there may exist a continuum between the two
> states where the brain can utilise X amount of analogue and Y amount of
> binary processing, such that X + Y = 1. The possibilities are amazing when
> one thinks about it - it is one of the reasons I enjoy Neuroscience so
very
> much.
>
> T.L.S.
>
>
> Richard Norman <rsnorman at mediaone.net> wrote in message
> news:Sghq5.5861$_e4.303769 at typhoon.mw.mediaone.net...
> > There are several major assumptions in your way of thinking that I don't
> > really understand.  The question about creating an "artificial sentient
> > being" only the ultimate.
> >
> > Why should graded or analog processes be any less knowable or
> understandable
> > than discrete or digital ones? In the Newtonian universe, everything is
> > continuously variable -- space, time, mass, force, momentum, energy.
> > And phenomena in the macroscopic world of modern physics are so large
> > compared to quantal steps, that they might as well be continuously
> variable.
> > That doesn't mean that these things are incomprehensibly complex, only
> that
> > we use a real number, a continuously variable measure, to describe them.
> > And nothing in our behavior is really discrete. I am not "happy" vs. not
> or
> > "angry" vs. not.  Instead, my behavior shows differing degrees of
> happiness
> > or anger that fluctuates all the time.  So I just am not sure why the
> > absence of
> > digital states makes any difference in how we see or understand the
world
> > around us.
> >
> > As for two questions you raise:  "How can a seemingly random event give
> rise
> > to the coherence patterns of mental activity" or can an "artificial
> > sentient being be created using ... computer technology" -- these
> > are not really questions that we are anywhere near ready to approach.
> > I would prefer rephrasing them:  "How can the big bang give rise to
> > the coherence patterns of mental activity -- and to the apparently
> sentient
> > beings we claim to be?"  The answer, of course, lies in evolution.  But
> > there are a lot of interesting details left to be worked out!
> >
> > "Theophilus Samuels" <theophilus.samuels at btinternet.com> wrote in
message
> > news:8oc45p$rqp$1 at plutonium.btinternet.com...
> > > Tell me something, I've just finished reading your reply and I would
> like
> > to
> > > know what you think of the following. If the brain processess
> information
> > in
> > > both analogue and binary forms (more in the case of the former,
> according
> > to
> > > u ;-)), then is it truly a hopeless cause to ever think that a
> artificial
> > > sentient being can be created using the limited computer technology we
> > have
> > > access to??? I mean, a graded response must on the molecular scale be
> > > incomprehensibly complex on each occasion that it is initiated, and
thus
> > no
> > > correlation will be ever be found between one graded response and the
> > > situation that it may produce (i.e. an emotion for example) - I
suppose
> > this
> > > also depends on whether u believe that information can be processed on
> > such
> > > a microscopic scale.
> > >   I respect and know that the brain does indeed possess graded
> responses,
> > > and as I have said, each one must on the molecular scale be unique and
> > thus
> > > makes understanding the phenomenon of consciousness totally beyond our
> > > grasp. Does this make sense? How can a seemingly random event give
rise
> to
> > > the coherence patterns of mental activity? Is this question
answerable?
> > >
> > > T.L.S.
> > >
> > > Richard Norman <rsnorman at mediaone.net> wrote in message
> > > news:iEUp5.1660$_e4.240409 at typhoon.mw.mediaone.net...
> > > > I think you are missing the importance of what we two Richards are
> > > > saying.  The fact is that there are, indeed, large numbers of
neurons
> > > > that work completely without action potentials in any form.  And
many
> > > > neurons that do produce action potentials still interact with
> > > > dendro-dendritic synapses that are completely graded.  It is quite
> > likely
> > > > that most of the important "computations" done by the nervous system
> > > > are in this graded format.  Only when a message must be transported
> > > > some distance is it translated into the binary form of the
all-or-none
> > > > action potential.
> > > >
> > > > "Theophilus Samuels" <theophilus.samuels at btinternet.com> wrote in
> > message
> > > > news:8o91ca$6ro$1 at plutonium.btinternet.com...
> > > > > I understand what you are trying to say and I agree with you. The
> > > original
> > > > > thought was that the 'brain is sorta like a computer that is not
> based
> > > on
> > > > > binary' - what exactly was this fellow trying to say?
> > > > >   Sometimes, one should break down a problem into its simplest
> > > components.
> > > > > The neuron initiates an action potential at the axon hillock and
> this
> > > > > 'event' can be manipulated by other synapses, be they inhibitory
or
> > > > > excitatory via dendrodendritic, axosomatic or even axoaxonic
> > > interactions.
> > > > > Here is a basic fact, only when the potential difference across
the
> > > > membrane
> > > > > component reaches the threshold potential is an action potential
> > > > initiated -
> > > > > given, that graded action potentials can occur without reaching
this
> > > > > potential, but again remember, in the brain what is the use of a
> > graded
> > > > > potential in the realms of information processing?? Here is where
I
> > > think
> > > > we
> > > > > have got our wires crossed, I am referring to the way information
is
> > > > handled
> > > > > within the brain.
> > > > >   Thus, I am referring to is the 'all or nothing' response
generated
> > by
> > > > > neurons in the form of the overstated AP. This is what is
ultimately
> > > used
> > > > to
> > > > > carry information from one part of the brain to the other! For
> > instance,
> > > > > information coming in from the left visual field is processed by
the
> > > right
> > > > > occipital cortex and vice versa. Thus, the only way for both
> occipital
> > > > areas
> > > > > to communicate with each other is via the corpus callosum, or more
> > > > > specifically via AP travelling through these myelinated axons -
> there
> > is
> > > > the
> > > > > key, ACTION POTENTIALS, or in computer terms ON events, there is
no
> > way
> > > > that
> > > > > graded AP can give rise to corticocortical interactions on such
> > scales.
> > > > >   To close, what I am saying is that ultimately the first and
> foremost
> > > > level
> > > > > of processing within the brain can only be the ON or OFF AP fired
at
> > > > > DIFFERENT FREQUENCIES - there is where we shall find the greatest
> > > > > difference, a difference that no computer engineer will probably
be
> > ever
> > > > to
> > > > > replicate, that of AP firing frequencies to process information.
> > > > >
> > > > > T.L.S.
> > > > >
> > > > >
> > > > > "Richard L. Hall" <rhall at webmail.uvi.edu> wrote in message
> > > > > news:v0422080ab5cc75761001@[146.226.154.76]...
> > > > > >
> > > > > > Yep...most brain cells use grade synaptic transmission driven by
> > > > > > slight changes in potential.  Even at "resting" potentials some
> > cells
> > > > > > release neurotransmitter.  Thus, synaptic interactions merely
> modify
> > > > > > a continuous process.  This has the advantages of:
> > > > > >
> > > > > > 1.  reducing the response time of the system,
> > > > > > 2.  reducing the requirements for large signal to noise
resolution
> > > > > > while increasing
> > > > > >        information content,  and
> > > > > > 3.  averaging the rates of energy consumption so you do not have
> > > > problems
> > > > > like
> > > > > >       running out of fuel just when you need maximal computing
> > power.
> > > > > >
> > > > > > The response of an on/off system driven by action potentials
would
> > be
> > > > > > complicated by refractory periods and make it hard to summate
> > > > > > information....timing is everything.
> > > > > >
> > > > > > A system that is constantly transmitting information essentially
> > > > > > integrates signals and noise.  Since noise is random, it falls
out
> > > > > > over time making it possible to detect smaller signals.  As a
> bonus,
> > > > > > a constantly active system can either increase or DECREASE in
> > > > > > activity giving even more flexibility and information value.
> > > > > >
> > > > > > The brain has virtually no energy reserves and without this
> > > > > > adaptation, a sudden increase in energy demand would be fatal.
> > > > > >
> > > > > > Nifty stuff this evolution.
> > > > > >
> > > > > > rlh
> > > > > >
> > > > > > >Surely it IS correct.  Action potentials are widely
misunderstood
> > to
> > > be
> > > > > > >the be-all and end-all of nervous system information
processing.
> > > They
> > > > > are,
> > > > > > >indeed, useful and important for transmitting information over
> any
> > > > > "large"
> > > > > > >distance, that is a few millimeters or more.  But at the
cellular
> > > > level,
> > > > > a
> > > > > > >few
> > > > > > >millimeters is an enormous distance and graded "analog"
> potentials
> > > > along
> > > > > > >with graded (analog) transmitter release form a large portion
of
> > the
> > > > > > >information processing in local circuits.  The best example of
> this
> > > is
> > > > > > >perhaps
> > > > > > >the vertebrate retina, where the receptor cells (rods and
cones),
> > the
> > > > > > >horizontal
> > > > > > >cells, and the bipolar cells all do their thing without action
> > > > > potentials.
> > > > > > >The
> > > > > > >amacrine cells produce half-hearted action potential and it is
> only
> > > the
> > > > > > >retinal
> > > > > > >ganglion cells, who must send their output a long distance down
> the
> > > > optic
> > > > > > >nerve, that produces honest-to-goodness classical action
> > potentials.
> > > > > > >
> > > > > > >And in days past, there were large numbers of analog computers
in
> > use
> > > > > > >doing all kinds of engineering computations and simulations --
> > adding
> > > > and
> > > > > > >subtracting, multiplying and dividing, even integrating and
> > > > > differentiating
> > > > > > >in
> > > > > > >the solution of complex systems of differential equations
without
> > the
> > > > > need
> > > > > > >for a "On/Off" events.  Indeed, the very term "digital
computer"
> > was
> > > > > > >necessary
> > > > > > >to distinguish the newcomers from the ordinary, more common
> analog
> > > > > > >variety.
> > > > > > >
> > > > > > >
> > > > > > >"Theophilus Samuels" <theophilus.samuels at btinternet.com> wrote
in
> > > > message
> > > > > > >news:8o6f77$ri1$1 at plutonium.btinternet.com...
> > > > > > >  > > > It sounds as though the brain is sorta like a computer
> that
> > > is
> > > > > not
> > > > > > >based
> > > > > > >  > on
> > > > > > >  > > > binary.
> > > > > > >  > >
> > > > > > >  > > Right.
> > > > > > >  >
> > > > > > >  > Surely that is incorrect? The fundamental principle used by
> > > > computers
> > > > > > >relies
> > > > > > >  > on 'ON' and 'OFF' events, or in binary form, 1's and 0's.
Now
> > > > > consider the
> > > > > > >  > neurons working within the brain. Essentially, all they do
is
> > > > > initiate
> > > > > > >  > action potentials that either produce excitatory or
> inhibitory
> > > > > responses -
> > > > > > >  > 1's or 0's. Thus, you can actually say that the brain does
> > indeed
> > > > > work on
> > > > > > >a
> > > > > > >  > binary system IN principle. The MAIN difference between the
> > > binary
> > > > > system
> > > > > > >  > used within a CPU and a brain, is that neurons are capable
of
> > > > firing
> > > > > at
> > > > > > >  > differing rates, i.e. information in the brain is FREQUENCY
> > > coded.
> > > > So
> > > > > to
> > > > > > >  > reiterate, the firing of neurons does indeed use a binary
> > > principle
> > > > > to
> > > > > > >  > create, well...., you or I.
> > > > > > >  >
> > > > > > >  >   T.L.S.
> > > > > > >  >
> > > > > > >  > <dag.stenberg at helsinki.nospam.fi> wrote in message
> > > > > > >  > news:8o55if$nvm$1 at oravannahka.helsinki.fi...
> > > > > > >  > > Phoenix <phoenix42 at uswest.net> wrote:
> > > > > > >  > > > It sounds as though the brain is sorta like a computer
> that
> > > is
> > > > > not
> > > > > > >based
> > > > > > >  > on
> > > > > > >  > > > binary.
> > > > > > >  > >
> > > > > > >  > > Right.
> > > > > > >  > >
> > > > > > >  > > > Since the computers we
> > > > > > >  > > > currently used are binary based, I wonder if we'll have
> to
> > > > > develop new
> > > > > > >  > > > computers that aren't binary based ...
> > > > > > >  > >
> > > > > > >  > > Before digital computers, there were analog computers.
> > > > > > >  > >
> > > > > > >  > > Dag Stenberg
> > > > > > >  >
> > > > > > >  >
> > > > > >
> > > > > > Richard L. Hall, Ph.D.
> > > > > > Comparative Animal Physiologist
> > > > > >
> > > > > > University of the Virgin Islands
> > > > > > 2 John Brewers Bay
> > > > > > St. Thomas, U.S.V.I. 00802
> > > > > >
> > > > > > 340-693-1386
> > > > > > 340-693-1385 FAX
> > > > > >
> > > > > > rhall at uvi.edu
> > > > > >
> > > > > > "Live life on the edge...the view is always better"  rlh
> > > > > >
> > > > > >
> > > > > > ---
> > > > >
> > > > >
> > > >
> > > >
> > >
> > >
> > >
> > >
> >
> >
> >
> >
> >
> >
>
>







More information about the Neur-sci mailing list