Other Definitions
phosphene (dict)
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PhosphenePhosphenes are signals from the neurons of the retina to the visual cortex of the brain which are interpreted by the brain as lights and visual patterns, but are not caused by visual light. They can be produced by neurons randomly firing (similar to what causes muscle twitches) and a variety of other causes. An easy way of producing phosphenes is to gently press the palms of your hands against the eyeballs with closed eyelids. Different types of visual phenomena can then be "seen", with a stronger effect the longer you keep your eyes closed. If you are in a darkened environment and open your eyes, the phosphenes become mixed with the normal field of vision. Phosphenes can also be elicited (less commonly) by various diseases of the retina and nerves. Phosphenes are examples of entoptic phenomena, i.e visual images which arise within the human visual system, and not as a reflection of the world around us. Different types of hallucinations are other examples of entoptic experiences. In 1988, J. D. Lewis-Williams and T. A. Dowson published an article about phosphenes and other entoptic phenomena. They argued, among other things, that non-figurative art of the Upper Paleolithic depicts actual visions of phosphenes and neurological "form constants", problably enhanced by hallucinogenic drugs. External links
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