The dreamachine (or dream machine) is a stroboscopic flicker device that produces visual stimuli. Artist Brion Gysin and William S. Burroughs's "systems adviser" Ian Sommerville created the dreamachine after reading William Grey Walter's book, The Living Brain. In its original form, a dreamachine is made from a cylinder with slits cut in the sides. The cylinder is placed on a record turntable and rotated at 78 or 45 revolutions per minute. A light bulb is suspended in the center of the cylinder and the rotation speed allows the light to come out from the holes at a constant frequency of between 8 and 13 pulses per second. This frequency range corresponds to alpha waves, electrical oscillations normally present in the human brain while relaxing. A dreamachine is "viewed" with the eyes closed: the pulsating light stimulates the optical nerve and alters the brain's electrical oscillations. The user experiences increasingly bright, complex patterns of color behind their closed eyelids. The patterns become shapes and symbols, swirling around, until the user feels surrounded by colors. It is claimed that using a dreamachine allows one to enter a hypnagogic state. This experience may sometimes be quite intense, but to escape from it, one needs only to open one's eyes.