Today, the neurological mechanism behind these reactions is more or less understood. At any given moment, our brain is receiving a torrent of sensory information—visual, auditory, tactile, and so on. We are so accustomed to this stream of input that when it gets cut off, our brain essentially produces its own stimuli. It identifies its own patterns, combining any scant blip in the visual cortex with images stored in memory to devise scenes that may be intensely vivid, however disconnected from present reality. During one particularly illuminating experiment in 2007, researchers at the Max Planck Institute for Brain Research in Frankfurt collaborated with a German artist named Marietta Schwarz, who had volunteered to live with a blindfold on for twenty-two days. Blindversuch (Blind Study), as Schwarz called her project, was part of a larger art project called Knowledge of Space, which incorporated interviews with blind people on perception, image, space, and art. Schwarz sat blindfolded in the laboratory, recording into a Dictaphone a granular, real-time diary of everything that was happening in her brain. She reported an array of hallucinations, including intricate abstract patterns, such as bright amoebas, yellow clouds, and animal prints. The researchers, meanwhile, used an fMRI scanner—functional magnetic resonance imaging, which tracks changes in blood flow in the brain—to follow the neurological operations behind her hallucinations. Despite the total absence of visual input, Schwarz’s visual cortex lit up like a lantern, exactly as it would if she weren’t blindfolded.