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jim >From the Chicago Tribune Seeing more than meets eye Science finding hallucinations may be reflection of brain pathways By Ronald Kotulak Tribune science reporter January 1, 2002 Near-death experiences, in which people believe they see the bright light of heaven at the end of a tunnel, may be nothing more than the brain cells that process vision lighting up in such a way so as to reveal the circular pattern of how they are wired together. New research also indicates that prehistoric cave and rock art depicting spirals, zigzags and other geometric forms may have been done by artists experiencing the same kind of drug-induced hallucinations that people today have when they take LSD, mescaline, Ecstasy and other psychedelic compounds. A visual hallucination is defined as seeing something that's not there. They are relatively common, and almost all cultures from prehistoric times on have used drugs to induce hallucinations for religious, healing and artistic purposes. But science now suggests that near-death images and other hallucinations involving geometric patterns are really there-- on the inside of the brain. Inducing creative mood People like Arthur Conan Doyle, Aldous Huxley, Cary Grant, Allen Ginsberg, Tallulah Bankhead, the Beatles, Charles Dickens, Timothy Leary and Salvador Dali, who used hallucinogens in the hopes of inducing a creative mood, were actually lighting up their brain wiring. "[It] surged upon me an uninterrupted stream of fantastic [kaleidoscopic-like] images of extraordinary plasticity and vividness," is how Albert Hoffman, the brilliant Swiss chemist, described his first experience with LSD, a compound he had synthesized in 1938. Hallucinations can also be caused by anesthetics, fatigue, hunger, stress, alcohol, fever, adverse drug reactions, sleep deprivation, bright flickering lights and even pressure on the eyeballs. Normally, the 100 million neurons of the credit-card size visual cortex at the back of the head convert what our eyes see into edges color, depth and other features, and then reassemble the pieces into recognizable scenes of the outside world. The process works fast. About 40 milliseconds after seeing an object, edge detectors are activated and in another 40 milliseconds the edges become pieced together into contours and the beginnings of surfaces. This information goes to other parts of the brain to be compared with stored memories. In far less than a second you've basically solved the problem of vision, of remembering, recognizing and sorting out what the object is. In the case of a hallucination, this does not happen. Through the action of drugs or other influences, the edge detectors become disengaged from the rest of the network and begin firing on their own. The resulting hallucination reflects the pinwheel pattern of brain cells that process lines, curves and other geometric shapes, providing a remarkable view of the physical architecture of the visual cortex, according to recently published findings by Jack Cowan of the University of Chicago and Paul Bressloff of the University of Utah. "It's almost like seeing your own brain through a mirror," Cowan said. "You're basically seeing patterns that your own brain is making." 4 basic groups Cowan, who is a mathematician and a neurologist, has been studying hallucinations for 20 years. He was intrigued by the work of another U. of C. scientist, Heinrich Kluver, who in the 1920s and 1930s classified the drawings of people experiencing drug-induced hallucinations into four basic categories--tunnels and funnels; spirals; lattices; and cobwebs. Based on new findings from optical imaging, in which scientists can actually see which neurons light up in the visual cortex of cats and monkeys when they view different lines and contours, Cowan, Bressloff and their colleagues developed a mathematical model that can accurately predict the shapes of different hallucinations. "We calculated that given the kinds of anatomy in the visual cortex, there are only four kinds of patterns it will make when it goes unstable," Cowan said. "It turns out that those four kinds of patterns we get from the math correspond exactly to the four classes of patterns that Kluver ended up with based on his looking at the drawings." Terry Sejnowski, director of the Salk Institute's Computational Neurobiology Laboratory, said the work of Cowan and Bressloff could have wide application in the areas of artificial intelligence and artificial vision. "They have created a mathematical model which replicates surprisingly well the states that the brain gets into when it's having visual hallucinations," he said. "These hallucinatory states are really abnormal conditions. Sometimes you learn a lot about a complex system from the conditions which occur when it breaks down or when it's not operating under normal conditions." The mathematical study of vision is also helping to explain near-death experiences. Essentially they are physical representations of striplike columns of neurons in the visual cortex that form a tunnel pattern. "What actually happens when somebody takes a drug is the first thing they experience is a very bright light in the center of the visual field, which is very reminiscent of this sort of light in the tunnel when people think they see heaven beckoning in the distance," Bressloff said. "What seems to happen is that this bright light spreads across the visual field and from that state then this structure emerges which is the seed for the hallucination pattern," he said. Drug-induced drawings Since spirals, tunnels, zigzags and other hallucinatory patterns can be found in the art of almost all cultures and go back more than 30,000 years, many anthropologists speculate that they were done under the influence of hallucinogenic drugs or self-induced trances, and that these experiences served as the origin of abstract art. The foremost masters of hallucinogenic experiences are shamans, ritual practitioners in hunting-and-gathering societies who enter altered states of consciousness to achieve a variety of ends that include healing the sick, foretelling the future, meeting spirit-animals, changing the weather and controlling animals by supernatural means, according to Jean Clottes, scientific adviser to the French ministry on prehistoric art, and David Lewis-Williams, professor of cognitive archeology at the University of Witwatersrand in Johannesburg, South Africa. In their study of shamans, religious mystics and visionaries around the world, Clottes and Lewis-Williams found that while drugs are widely used to induce hallucinations, trances are also used to produce unusual mental imagery. Trances can be induced through sensory deprivation, prolonged social isolation, intense pain, vigorous dancing and insistent, rhythmic sound, such as drumming and chanting. 3 stages of trances In their book, "The Shamans of Prehistory: Trance and Magic in the Painted Caves," Clottes and Lewis-Williams outline three stages of trance. In the first stage trance, people "see" geometric forms, such as dots, zigzags, grids, parallel lines, nested curves and meandering lines. In the second stage, subjects try to make better sense out of the geometric imagery by illusioning them into objects of religious or emotional significance, such as construing a zigzag line into a snake. The third stage is reached via a vortex or tunnel, at the end of which is a bright light. When people emerge from the tunnel they find themselves in a bizarre world where geometric patterns become mixed with monsters, people and settings. It is in this stage where the drawings of humans with animal features occur. Clottes and Lewis-Williams concluded: "We emphasize that these three stages are universal and wired into the human nervous system, though the meanings given to the geometrics of Stage 1, the objects into which they are illusioned in Stage 2, and the hallucinations of Stage 3 are all culture-specific, at least in some measure, people hallucinate what they expect to hallucinate." Copyright � 2001, Chicago Tribune _________________________________________________________________ Get your FREE download of MSN Explorer at http://explorer.msn.com/intl.asp. --- You are currently subscribed to tips as: [EMAIL PROTECTED] To unsubscribe send a blank email to [EMAIL PROTECTED]
