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...Sorry everybody,I'm having one of my compulsorycut & paste crisis! http://www.dxarts.washington.edu/pop_sci/images/phosphene.jpgPhosphenes are a visual and neurological phenomenon common to all mankind. They are the undulating (aurora like) geometric patterns and moving points of colored light we often experience when we close our eyes, or when we keep them open while adapting to a dark room. This mesmerizing effect can also be produced if we press our fingers firmly on our eyes long enough to stimulate the same retinal process. Electrophosphenes are a method of electrically reproducing the same visual effect as phosphenes, but with a greater range of patterns, color subtlety and precision. Electrophosphenes are created by placing small galvanic electrodes on the temples near each eye, and applying a tiny voltage (one volt at one milliampere current) that is pulse modulated at frequencies typically between 5-100 Hz. The locus of the effect is in the retina, and available evidence suggests that tiny induced currents in the retina elicit visual responses similar to those resulting from light stimulation. Electrophosphenes have been studied for more than a century, including extensive investigation by early scientific luminaries such as Benjamin Franklin and Johannes Purkinje. However, the majority of experimental arrangements have typically used man-made electrical and pulse modulation systems to produce the effect. The proposed system for the Altamira project would instead use naturally occurring celestial objects (pulsars) as the primary electrophosphene signal input. (A substantial percentage of catalogued pulsars produce pulse frequencies and pulse shapes perfect for generating unique forms of electrophosphenes).from: http://www.dxarts.washington.edu/pop_sci/