[Neuroscience] Re: A Purely-Electronic Brain -- Possible?

r norman via neur-sci%40net.bio.net (by r_s_norman from _comcast.net)
Sat Apr 21 07:04:37 EST 2007


On Sat, 21 Apr 2007 04:02:11 GMT, "Benjamin" <Benjamin from verizon.net>
wrote:

>"r norman" <r_s_norman from _comcast.net> wrote in message 
>news:klhi23pasls517arrgok1ek2hr1kb7669s from 4ax.com...
>| On Sat, 21 Apr 2007 00:15:17 +0200, Josip Almasi <joe from vrspace.org>
>| wrote:
>| [...]
>
>| I recall Roger Sperry describing in
>| class some 45 years ago his
>| experiments showing how general
>| electric fields could not be responsible
>| for "gestalt" phenomena -- he short-
>| circuited brain regions with tantalum
>| wires and isolated brain regions with
>| mica insulators but neither intervention
>| had any effect on cortical function.
>| [...]
>
>I've only been skimming this thread, so
>my comments will be out-of-context [and
>I'm not agreeing with anything in what
>I've only skimmed.]
>
>The ionic conductances are necessary
>for 'normal' neuronal function, which ["of
>course"] includes 'normal' cortical function.
>
>And the ionic conductances are literally
>a dynamically-formed 'electric field' that's
>tunable via globally-integrated TD E/I-
>minimization as I've discussed in form-
>er posts here in b.n.
>
>Your post is the first I've heard of it, but
>to do what Sperry claimed(?) [as above],
>one would have to eliminate all ionic cond-
>uctances.
>
>The problem with that is that what's
>left is not a "brain", but only a bunch
>of dead stuff.

As I recall, the explanation for the Gestalt theory (or at least one
explanation) was that there were electrical fields at work operating
over regions of the brain.  Sperry took a brain (rat, I believe, but
you could look it up) and threaded a large number of tantalum wires
through it which should readily equalize the electrical field
potential at all points.  He took another and make numerous slits (in
directions to avoid cutting major axonal pathways) and inserted mica
sheets into the slits.  That would insulate one area from another,
preventing the electric field from spreading across the gaps.  He did
not interfere with the intracellular ionic conductances so each cell
could function normally.

I was commenting on theories that propose overall electromagnetic
fields as important in brain operation.  In particular, we know that
one cubic millimeter of mammalian brain may have several thousand
neurons, each doing rather distinct and specialized computations (or
whatever you want to call neuronal activity).  Is there any known
mechanism that would allow for fine variations of the electromagnetic
field so that points just a few dozen micrometers apart have very
distinct field values?   Is there any known mechanism whereby small
changes in the electromagnetic field can cause variation in nerve
activity?People live and work in environments where there are strong
electrical and magnetic fields and electromagnetic fields without
noticeable effect on behavior.   Magnetic stimulation requires pretty
hefty field strength, something far out of the normal range. 




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