Exogenous Zeitgebers Flashcards
(3 cards)
Supporting evidence for the role of exogenous zeitgebers in the sleep-wake cycle
Supporting evidence for the role of exogenous zeitgebers in the sleep-wake cycle is provided by Vetter et al. (2011). During the darker months of January and February, an
experimental group of office employees was exposed to brighter lighting (8000K – cool hue) whilst a control group were exposed to regular lighting (4000K – warm hue). Over a 5-week period the sleep/wake activity of the experimental group became synchronised to the onset of bright office lighting, whilst in the control group sleep/wake activity was synchronised to
natural dawn. These findings suggest that light is the dominant zeitgeber for the human clock and especially bright (cool hue) artificial light.
Refuting evidence for the role of social cues as exogenous zeitgebers in the sleep-wake cycle
Refuting evidence for the role of social cues as exogenous zeitgebers in the sleep-wake cycle is provided by Miles et al. (1977). They documented the problems of a 28-year old man (J.X.) who was blind from birth and had a circadian rhythm of 24.9 hours. Despite being exposed to various social cues as such as clocks, he had great difficulty reducing his sleep-wake cycle to 24 hours. This made it difficult for him to function and he had to take stimulants and sedatives to synchronise his free-running biological clock to precisely 24 hours. This suggests that socially-based exogenous zeitgebers have a limited influence on the sleep-wake cycle.
An advantage of research into exogenous zeitgebers is the practical application to mobile
phone use.
An advantage of research into exogenous zeitgebers is the practical application to mobile
phone use. The bright white light (cool hue) used by LED mobile phone screens can reset SCN
activity which reduces melatonin production and prevents a person from becoming sleepy. Mobile phone users can be advised to avoid using their device in the hours before sleep. Many mobile phones include a “night mode” which dims the screen and provides a warm hue filter to prevent brighter cool hues from disrupting the onset of sleep. This application highlights the advantage of reducing the complexities of the sleep-wake cycle to focus on role of light.
