Date: Mon, 18 Oct 1999 08:26:29 -0400
From: Bill Benzon <bbenzon@mindspring.com>
To: Memetics Listserve <memetics@mmu.ac.uk>
Subject: Re: Inernal meme?
"Mark M. Mills" wrote:
>
> Bill Benzon recently suggested it would be impossible to make any
sense of the
> raw bit stream between two nerve cells, but I posted a reference
yesterday to
> success interpretation of such a bit stream.
>
(<http://news.bbc.co.uk/hi/english/sci/tech/newsid_468000/468857.stm>http:/
> /news.bbc.co.uk/hi/english/sci/tech/newsid_468000/468857.stm) The
scientists
> involved report converting the bit stream between cat thalamus nerve
cells
> into
> recognizable moving objects via computer processing.
Granted that the news article on this experiment doesn't say much, still
I don't
think it has much bearing on my earlier assertion. As far as I can
tell, the
results are similar in kind to tapping into a cable TV line and
displaying the
signal on a CRT. We think nothing of tapping in to cable TV lines
because we
understand that technology quite well. The cat experiment is remarkable
because
the "technology" (cat visual system) is quite different in kind from our
artificial technology. But, all that's going on is that we're tapping
into a
signal being transmitted from point A (the retina) to point B (to
occipital
cortex) and deriving an image from it. This experiment tells us nothing
about how
cats perceive and recognize objects and events. The only perception &
recognition
in this experiment is that the experimenters do when they look at the
video tape.
Basically, visual images are registered in the retina, where they are
processed
and sent through the optic nerve to the brain. They go first to the
lateral
geniculate nucleus (LGN), then to the thalamus, and from there to the
visual
cortex. We don't have any image interpretation and recognition until we
get to
the visual cortex; that's were you have to look for visual memes.
Visual
processing prior to the cortex seems to be a matter of noise reduction,
not
perception and recognition.
One of the interesting things about the nervous system is that, starting
with
peripheral sense organs (the retina, skin surface, cochlea, etc.) the
projections
from one center to the next (e.g. retina to optic nerve to LGN to
thalamus to
cortex) form a topic map. So, much of the information these
investigators got from
the thalamus was "encoded" in the spatial relations between the 177
cells they
tapped. If they got those relations scrambled it would have been
impossible to
make sense of the signals.
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