neurotransmitter storage (all or one?)

Richard L. Hall rhall at webmail.uvi.edu
Fri Aug 25 15:30:21 EST 2000


The "other Richard" speaks,

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


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