Segmented Sleep

Quote on Ultrashort Sleep Findings
From "Why We Nap," Claudio Stampi:
(Referring to a study in chapter 12; page 195)

The implications of what emerged from this series of studies are discussed in greater detail, within the broader context of a review on other polyphasic sleep studies, in Chapters 1 and 10. In brief, findings described in this chapter do not appear to contradict the following hypothesis:

Adult humans appear to have a natural ability to adapt to polyphasic sleep schedules.
The 4-hr ultradian cycle of sleep-wake pressure previously described may be an important factor in allowing adaptation to polyphasic patterns.
The sleep-wake system appears to show a high level of flexibility in terms of sleep timing and duration.
Polyphasic sleep may be a feasable, and perhaps the only, strategy allowing remarkable levels of sleep reduction during prolonged quasi-continuous work situations, without unduly compromising performance effectiveness.
This may be analogous to what is observed in a considerable number of mammalian species, particularly in those living in dangerous environments.
Further studies extended to a larger sample of subjects may provide powerful tools for developing sleep-wake schedules for individuals involved in irregular or quasi-continuous work situations.
These findings and hypothesis raise challenging questions concerning what is known about the regulatory mechanisms of sleep function.
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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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