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Hallucinations Lead To Insight Into The Visual Brain

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  • Steve Palmer
    Dear Friends and All, I checked this story out with an expert (thanks Lee) and am delighted, that it s the real deal. This is pretty interesting and important
    Message 1 of 1 , Jan 8, 2002
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      Dear Friends and All,

      I checked this story out with an expert (thanks Lee) and am delighted, that
      it's the real deal.

      This is pretty interesting and important news, for folks with visual
      impairments, although most of the folks I know who are blind, see far
      better, than the folks who are not.

      I had a few expierences with hallucinations in the 60's, and they certainly
      were an expierence, in how I percieved the world around me and within me.

      Cheers,

      Steve & Yofi

      Steven Palmer Disabled Advocate
      British Columbia, Canada
      E-Mail: spalmer@...

      * * * * * * * * * * * *


      Hallucinations Lead To Insight Into The Visual Brain

      Scientists are deducing the internal circuitry of the visual brain by
      mathematically reproducing the geometric hallucinations people see when
      they
      ingest mind-altering drugs, view bright, flickering lights or encounter
      near-death experiences.

      The findings by the University of Chicago's Jack Cowan, the University of
      Utah's Paul Bressloff and three of their colleagues provide new insights
      into
      the complexities of vision, the workings of the brain and even the origins
      of
      art.

      "We take it for granted, but seeing is an amazing process," said Cowan, a
      Professor in Mathematics and Neurology. "In something less than a second,
      we
      can see objects and classify them under all kinds of differing illumination
      from very dim to very bright. We're just scratching the surface of what's
      going
      on."

      The mathematical study of vision and the brain has been accepted for
      publication in the journal Neural Computation. Co-authoring the study were
      Martin Golubitsky, University of Houston and two of Cowan's former graduate
      students, Peter Thomas, Salk Institute for Biological Studies, and Matthew
      Wiener, National Institutes of Health.

      "We're trying to understand how the intrinsic circuitry of the visual
      cortex of
      the brain can generate patterns of activity that underlie hallucinations,"
      Bressloff said.
      These geometric hallucinations take the form of checkerboards, honeycombs,
      tunnels, spirals and cobwebs, a phenomenon originally studied as early as
      the
      1920s and 1930s by the late Heinrich Klüver, a pioneering University of
      Chicago
      neurologist.

      "Because we know how the eyes are wired to the visual cortex, we can
      calculate
      what the patterns actually look like there," said Cowan. "They correspond
      very
      closely to the patterns that people report seeing."

      A technique called "perturbation theory" proved crucial to reproducing the
      geometric patterns, Bressloff said. Also crucial was an understanding,
      based on
      recent advances in brain anatomy and physiology, of the strong short-range
      connections and weaker long-range connections between neurons in the visual
      cortex.

      "It is a situation where you have something strong and something else
      that's
      weak, so it perturbs the system," Bressloff said.

      The mathematics that models the perturbation is, coincidentally, similar to
      that used in calculating the Zeeman effect in quantum mechanics, which
      describes the physics of the subatomic world.

      "If you take hydrogen atoms and you put them in a weak magnetic field,
      their
      spectrum changes in ways that can be calculated," Cowan explained. "It's
      called
      the Zeeman effect." Bressloff noted, however, that "there's no quantum
      mechanics involved in the actual working of the brain."

      Academically trained in physics and electrical engineering, Cowan may be
      the
      world's only university faculty member who holds dual appointments in
      mathematics and neurology. In 1986, he organized one of the founding
      workshops
      of the Santa Fe Institute, a private, non-profit research and education
      center
      devoted to the study of complexity and complex adaptive systems. He became
      interested in geometric hallucinations in the late 1970s, when he realized
      that
      they may provide clues regarding the brain's circuitry.

      "Producing hallucinatory images in the brain could be understood in terms
      of
      spontaneous pattern formation in the brain," Cowan said. "The brain makes
      patterns of activity when it goes unstable." Such instabilities follow the
      ingestion of substances such as LSD, psilocybin and cannabis, which act on
      control networks in the brainstem that secrete noradrenalin, seratonin and
      dopamine, which in turn control brain states.

      "If there's any noise-random fluctuations of brain activity in the brain,
      it is
      amplified into a pattern that reflects the architecture of the brain. The
      brain
      just takes the noise and shapes it into a pattern," Cowan said. "In the
      case of
      geometric visual hallucinations this is a direct consequence of the pattern
      of
      connections in the visual cortex."

      Some researchers foresee the day that blind people will see again following
      the
      implantation of a vision computer chip in the brain.

      "We're a long way from that," Cowan said. "So far we've only described the
      interactions between edge detectors in the visual brain, but there are all
      kinds of things going on in the visual cortex. There's detection of color
      and
      movement and depth and texture and surfaces. The circuitry involved in all
      of
      that is complicated and needs to be worked out."

      Cowan, Bressloff and their colleagues are ready to continue the work.
      Bressloff
      said, "It's just the beginning of a long program of studying more and more
      complex hallucination patterns, trying to see how far we can go with
      deducing
      the intrinsic circuitry of the cortex."

      As for the origins of art, last June Cowan participated in a conference on
      the
      topic in Montana. Geometric designs are a common design element in cave
      paintings and prehistoric rock art the world over. Some experts trace the
      prehistoric origins of art to hallucinogenic experiences.

      "A lot of the imagery is clearly related to what people report seeing when
      they
      take hallucinogens," Cowan said. - By Steve Koppes


      [Contact: Steve Koppes]



      07-Jan-2002
      http://unisci.com/stories/20021/0107023.htm
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