Tuesday, January 24, 2006

Quote on the 4-hr Ultradian Cycle

From "Why We Nap," Claudio Stampi (pg 8):

Under less-structured environments multiple naps do occur throughout the 24 hr, and many subjects exhibit polyphasic sleep similar to that observed in nonhuman species. Such spontaneous naps do not recur randomly throughout the day. Rather, their striking regularity allowed speculation on the existence of an ultradian 4-hr component of the sleep-wake cycle that may be superimposed on the more robust circadian and midafternoon components. In fact, 4-hr cycles in sleep propensity have been found in many studies conducted in unstructured environments (e.g., Nakagawa, 1980; Zulley, 1988). These findings are probably not surprising to investigators familiar with the 4-hr sleep-wake pattern observed in infants. More recently, 4-hr cycles in the expression of SWS have also been found in the frequent daytime naps in a population of narcoleptics (see Chapter 15).

It is worth mentioning that anthropological studies conducted in tribes active at night show that human sleep can be highly polyphasic in certain cultures. Although they have different cultures and ways of life, both the Temiars of Indonesia and the Ibans of Sarawak have similar polyphasic sleep-wake behaviors (Petre-Quadens, 1983).

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