IUBio

Wavelet answer: Re: question: job of a neuron

John H John at faraway.com.au
Fri Sep 7 23:47:18 EST 2001


Thanks Richard,

I'm not in a position to judge the wavelet idea, and one of my internal
rules is to try (!) to avoid making judgements about things I don't
understand. Hence my final question about testing it against a simple
nervous system. That seems to me to be the next logical step in the exercise
and for the purposes of proving\disproving wavelets the best possible
strategy.




John H.

Richard Norman <rsnorman at mediaone.net> wrote in message
news:5sfhptkrmvm05edg0k8i57a07rcj5ojg33 at 4ax.com...
> On Fri, 7 Sep 2001 21:52:01 +1000, "John H" <John at faraway.com.au>
> wrote:
>
> >
> >"Ron Blue" <rcb5 at msn.com> wrote in message
> >news:009301c1362a$6144a6e0$ce02030a at RBlue...
> >>
> >> Unfortunately, the rules we learned in school don't seem to apply to
the
> >> real world.  Standard models are not standard, consider the summation
> >> in dendritic fields that would be dendrites talking to dendrites.
> >Normally
> >> information is thought to flow from dendrites to soma to axon to
dendrites
> >> but this
> >> is not always true.  Neurons did not read the same rules that we
> >> did.  Consider the resent observation that glial cells transmit
> >information
> >> when we
> >> were told that their job was to support neurons.
> >
> >
> >It is nice and easy to say that neurons transmit, glia and astrocytes
> >support, but the division exists in our heads abstractly, not concretely.
> >Glia are important regulators of neural transmission and astrocytes
probably
> >play some role also. For that matter, we need to remember that cytokines,
> >typically associated with immunological activity, also have a direct and
> >significant bearing on neural transmission. How does this all fare for
> >connectionist models of neural transmission, which imply direct
signalling
> >as the only means of neural transmission?
> >
> >For eg. Nitric Oxide. Nitric oxide acts as a neuro and immune modulator
not
> >through direct contact but through diffusion to various regions in the
> >immediate cellular region. It has a half life of circa 30 secs and
diffuses
> >rapidly, affecting not only the generating cell but often its immediate
> >neighbours. This effect on transmission will be contingent upon the
distance
> >of the 'target' to the site of nitric oxide generation,
> >the rate of NO diffusion through the cell cytoplasm, and the general
> >metabolic activity of the relevant cells at the time. 'Excess' NO can
make
> >all hell break loose then watch neural transmission struggle(the immune
> >mediated part). That's the trick though, the neural transmission can
remain
> >intact for a very long time, all the while with neurons dying all over
the
> >cortex and underlying metabolic processes  challenged.
> >
> >The primary goal of brains is not to 'process information' but to
generate
> >an appropriate response to environmental(internal and external)
> >contexts.Given the variety of metabolic contexts in which brains must
> >achieve this primary goal, I struggle with the idea that just observing
> >neuronal activity will give us ALL the insights into how neurons do their
> >work. The neuroscientists are well aware of this but too often I get the
> >impression that the AI people overlook this, preferring simply to think
> >about neural transmission as some
> >singular isolated process quite independent of the rest of the body. So I
> >wonder if Inhibitory neurotransmitters\modulators, which I believe
increased
> >in frequency as brains became more complex, play a key role in helping to
> >control noise.
> >
> >It is useful to remember that nervous systems evolved collectively,
neurons
> >and glia and astrocytes all having their part to play, not to mention the
> >rest of the body. Nervous systems must not only contend with their own
> >internally generated activity(including sensations) but also contend
> >with\incorporate other signal types from the body that can signficantly
> >modulate neural activity. Whatever neural transmission is, it must be
able
> >to cope with a plethora of signal types and volumes.
> >
> >What I like about your approach Ron is that it provides avenues to
> >overcoming the continual noise and fluctuating contexts under which
brains
> >must function. "Fuzzy processing" is the norm of brain function, not the
> >exception. What I would like to know is: can you test your model against
a
> >simple nervous system?
> >
> >John.
> >
> I agree with most everything you say -- and it is very well put --
> almost. Beyond your "liking Ron Blues approach (" do you really
> believe in wavelets?) a technical quibble.  You speculate whether
> inhibitory/modulatory processes increase in  frequency as "brains
> become more complex".  Actually, inhibitory and modulatory processes
> have been around for a very long time.  Consider the crustacean
> stomatogastric ganglion, about the smallest known neural system (some
> two dozen neurons).  It works entirely on inhibitory and modulatory
> interactions between the cells.   You can't get "simpler" than that,
> yet it is incredibly complex in cellular activity.





More information about the Neur-sci mailing list

Send comments to us at biosci-help [At] net.bio.net