The visual hallucinatory response to flickering polychromatic light.

Abstract

Our understanding of human visual perception generally rests on the assumption that conscious visual states represent, in some qualitative fashion, a complex interaction between spatially structured variations in the ambient optic array and our visual nervous systems. The existence of visual hallucinations in a number of pathologies (e. g. Kolmel, 1984) as well as in experimental contexts (Fechner, 1838; Benham, 1895; Herrmann & Elliott, 2001; Knoll & Kugler, 1959) questions the assumption that what we see in the environment is necessarily determined by spatial structure in the distal stimulus. Here we show that complex colour and form hallucinations are evoked by flickering light and that the type of hallucination varies with flicker frequency flicker phase and the occurrence of other flicker induced hallucinations. This evidence supports theories of consciousness that stress temporal aspects of perceptual processing.