”Photic stimulation at different frequencies has been found to produce complex perceptual responses and it has been shown that the complexity of the visual imagery is a function of stimulation frequency. The lower the frequency, the more complex the image, i.e., stimulation at the theta range (6 Hz), consistently produced the most complex visual imagery.

The purpose of this study was to assess the type and prevalence of the imagery produced by photic stimulation. Apparently, the response to photic driving can produce or induce complex dream-like images and scenes that are usually only perceived during sleep onset and dreaming.”

Excerpt from: “Photic stimulation produces a hypnagogic state” by Von Gizycki H, Jean-Louis G, Snyder M, Zizi F, Green H, Franconeri S, Gaglio J, Troia S, Spielman A, Nunes J, Taub H. Sleep Research 1997; 26: 269. The Psychophysiology Laboratory, College of Staten Island, CUNY; Sleep Disorders Center, City College of New York; Medical and Health Research Association of New York, Inc./ NDRI, Inc.