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Segmented sleep, sometimes referred to as Bifurcated sleep, is one of the earliest polyphasic schedules. It is also one of the 4 Biphasic schedules available. Aside from its role as the progenitor of Dual Core sleep, its creation ('''non-reducing''') was natural and dated back to the [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4763365/ preindustrial era] (1750-1850), making it roughly 250 years old as of today. In short photoperiods (less daytime hours and more night time hours), it was researched that human sleep is also [https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1365-2869.1992.tb00019.x naturally segmented]. What is commonly observed in this Segmented behavior is that people would often go to bed after sunset, wake up after some hours at night, stay awake for a couple hours, and then go back to bed until sunrise hours. Segmented sleep is still common nowadays, being involuntarily or voluntarily practiced by many in the world. Nowadays, '''naturally Segmented sleepers''' have a short wake gap between 2 cores (~1.5-3h) as a result of interrupted monophasic sleep, in the middle of the night. It only makes sense then, that sleepers would wake up feeling refreshed from the first core, do something at night, before they go back to sleep when sleepiness level rises enough.

Segmented sleep, sometimes referred to as Bifurcated sleep, is one of the earliest polyphasic schedules. It is also one of the 4 Biphasic schedules available. Aside from its role as the progenitor of Dual Core sleep, its creation ('''non-reducing''') was natural and dated back to the [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4763365/ preindustrial era] (1750-1850), making it roughly 250 years old as of today. In short photoperiods (less daytime hours and more night time hours), it was researched that human sleep is also [https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1365-2869.1992.tb00019.x naturally segmented]. What is commonly observed in this Segmented behavior is that people would often go to bed after sunset, wake up after some hours at night, stay awake for a couple hours, and then go back to bed until sunrise hours. Segmented sleep is still common nowadays, being involuntarily or voluntarily practiced by many in the world. Nowadays, '''naturally Segmented sleepers''' have a short wake gap between 2 cores (~1.5-3h) as a result of interrupted monophasic sleep, in the middle of the night. It only makes sense then, that sleepers would wake up feeling refreshed from the first core, do something at night, before they go back to sleep when sleepiness level rises enough.

Currently, the Polyphasic Discord Community has discovered more sleep mechanics regarding Segmented sleep. For starters, Segmented is one of the 5 schedules with '''only core sleeps''' (2) and '''no naps'''. The entire basis of Segmented sleep is constructed based on the sleep peaks. It is widely regarded that the early hours of the night (~9-10 PM, '''SWS peak'''), when natural melatonin secretion is kickstarted, quality SWS will largely benefit if sleep time begins around these hours. Throughout a lot of EEG readings of adapted sleepers, it is commonly seen that the first core sleep is highly SWS-oriented, while the second core sleep, being near sunrise hours (~6-9 AM, '''REM peak'''), has a strong propensity for densely populated REM sleep. The segmentation of the main monophasic core sleep into 2 core sleeps that align with the sleep peaks bolster the sleep quality with much deeper core sleeps, and allow for <u>some potential sleep reduction</u> with strict bedtime everyday. Since 2 core sleeps are already allocated to night hours (which is similar to monophasic sleep's distribution of sleep), no naps in the day are needed, because the amount of light sleep from both cores is sufficient to sustain wakefulness for the entire day.

Currently, the Polyphasic Discord Community has discovered more sleep mechanics regarding Segmented sleep. For starters, Segmented is one of the 5 schedules with '''only core sleeps''' (2) and '''no naps'''. The entire basis of Segmented sleep is constructed based on the sleep peaks. It is widely regarded that the early hours of the night (~9-10 PM, '''SWS peak'''), when natural melatonin secretion is kickstarted, quality SWS will largely benefit if sleep time begins around these hours. Throughout a lot of EEG readings of adapted sleepers, it is commonly seen that the first core sleep is highly SWS-oriented, while the second core sleep, being near sunrise hours (~6-9 AM, '''REM peak'''), has a strong propensity for densely populated REM sleep. However, on Segmented it is worth noting that some minor amount of REM sleep can still be present in the first core sleep, and the same for SWS in the second core. The segmentation of the main monophasic core sleep into 2 core sleeps that align with the sleep peaks bolster the sleep quality with much deeper core sleeps, and allow for <u>some potential sleep reduction</u> with strict bedtime everyday. Since 2 core sleeps are already allocated to night hours (which is similar to monophasic sleep's distribution of sleep), no naps in the day are needed, because the amount of light sleep from both cores is sufficient to sustain wakefulness for the entire day.

Even though it may look odd that both core sleeps last for 3.5h rather than the would-be 3h, or 4.5h, it was later explained that each core consists of 2 full sleep cycles plus an extra 30 minutes of sleep time to cover the '''statistically likely REM period''' (just like 5h and 6.5h core). The statistically likely REM period originates from ''Polyphasic Society'', and the evidence for it is very poor (eight monophasic readings). While its existence is questionable, it is still possible to see the effects from having the cores be 3.5 hours long. Another explanation for the 30m extension on each core is from the possibility that the cycles extend to roughly '''105m''' as compared to the standard 90m cycles in monophasic sleep. This would explain the viability of the schedule despite having fewer cycles.

Even though it may look odd that both core sleeps last for 3.5h rather than the would-be 3h, or 4.5h, it was later explained that each core consists of 2 full sleep cycles plus an extra 30 minutes of sleep time to cover the '''statistically likely REM period''' (just like 5h and 6.5h core). The statistically likely REM period originates from ''Polyphasic Society'', and the evidence for it is very poor (eight monophasic readings). While its existence is questionable, it is still possible to see the effects from having the cores be 3.5 hours long. Another explanation for the 30m extension on each core is from the possibility that the cycles extend to roughly '''105m''' as compared to the standard 90m cycles in monophasic sleep. This would explain the viability of the schedule despite having fewer cycles.