That's definitely true for many (not sure about "most") of the blind, but it depends on the source of their blindness. Circadian rhythms are maintained by the

That's definitely true for many (not sure about "most") of the blind, but it depends on the source of their blindness. Circadian rhythms are maintained by the Suprachiasmatic nucleus (See http://en.wikipedia.org/wiki/File:Gray773.png http://en.wikipedia.org/wiki/File:Gray773.png; the SCN is in the dark region below the chiasma). If light/dark information reaches this structure, then circadian cycles will be maintained. Remember also that most of the blind still perceive some visual information. They still see light and dark, or large shapes. Mind you, this is a completely different phenomenon from the blindsight that this article is about.