Re: Seeing More Than Meets The Eye

From: Joe Dees (
Date: Sat Jan 05 2002 - 02:00:50 MST

('binary' encoding is not supported, stored as-is) >Date: Thu, 3 Jan 2002 16:32:06 +0100
> Re: Seeing More Than Meets The Eye Anders Sandberg <>Reply-To:
>There has been some interesting modelling of hallucinatory patterns by
>Bard Ermentrout at University of Pittsburgh
>( and Paul Bressloff at Loughborough
>University (
>The idea is that drugs produce disinhibition in the visual cortex, which
>leads to pattern formation. The fun thing is that you can model this
>essentially as an ordinary reaction-diffusion system (there is a local
>nonlinear interaction between excitation and inhibition, and they
>diffuse with slightly different diffusion constants) which produces
>spots, lines, hexagons and all the other usual patterns you see in
>nonlinear science textbooks across the virtual cortex.
>But since there is a nonlinear map between our visual field and the
>cortex, a straight line of cortical activity would not appear to us as a
>straight line, but a spiral. Paul showed that the most likely patterns
>also correspond well to many common hallucinations, and when they moved
>many common animated hallucinations appear. More complex interactions
>between direction sensitive cells produce spiderweb patterns and so on.
>Very elegant models.
>It seems likely that since we all share the same basic visual hardware,
>its modes of instability and resonance would affect us across culture,
>especially during early childhood when the developing visual system
>seems extra unstable. Many such phenomena are likely useful - the
>spontaneous waves across the retina during fetal development are
>believed to train the visual cortex for example.
Thanx for the references.
>Anders Sandberg Towards Ascension!
>GCS/M/S/O d++ -p+ c++++ !l u+ e++ m++ s+/+ n--- h+/* f+ g+ w++ t+ r+ !y

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