- Also known as Eigenlicht, light-dust, light chaos, dark light, brain light, and idioretinal light. The term Eigengrau comes from the German eigen (one's own), and grau (gray), and translates loosely as 'intrinsic gray'. The term was introduced in or shortly before 1860 by the German psychologist Gustav Theodor Fechner (1801-1887) to denote the disorganized motion of greyish colour seen in perfect darkness. It has traditionally been assumed that Eigengrau is mediated by action potentials sent along the optic nerve, whether or not derivative of "visual noise produced by the retina. However, empirical findings suggest that the thermal isomerization of the retinal pigment molecule rhodopsin may be responsible for producing this visual noise. An alternative hypothesis suggests that Eigengrau is mediated by the spontaneous release of neuro-transmitters within the visual pathways and/or striate cortex. It has been argued that Eigengrau is the substratum out of which visual "hypnagogic hallucinations and sleep dream visions arise. Eigengrau is either classified as a "retinogenic phenomenon, a "closed-eye hallucination, or a type ofvisual noise.ReferencesFechner, G.T. (1860). Elemente der Psychophysik. Leipzig: Breitkopf und Härtel.Filehne, W. (1885). Ueberden Entstehungsort des Lichtstaubs, der Starrblindheit und der Nachbilder. Graefes Archiv für klinische und experimentelle Ophthalmologie, 31, 1-30.
Dictionary of Hallucinations. J.D. Blom. 2010.