Zeitgeber Hierarchy in Humans: Resetting the Circadian Phase Positions of Blind People Using Melatonin

Abstract

Four blind individuals who were thought to be entrained at an abnormal circadian phase position were reset to a more normal phase using exogenous melatonin administration. In one instance, circadian phase was shifted later. A fifth subject who was thought to be entrained was monitored over four years and eventually was shown to have a circadian period different from 24 h. These findings have implications for treating circadian phase abnormalities in the blind, for distinguishing between abnormally entrained and free‐running blind individuals, and for informing the debate over zeitgeber hierarchy in humans.

• Circadian rhythms
• Entrainment
• Totally blind people
• Melatonin
• Melatonin phase response curve