Testing shows human blood chemistry during the nocturnal waking period of biphasic sleep exhibits hormone levels similar to a lactating mother

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Neurobiological research by Dr. Lindsay Schwarz demonstrates that specific midline thalamic circuits regulate behavioral switches between forward engagement, freezing, and retreat in response to predatory threats

Historian A. Roger Ekirch documented that pre-industrial human sleep was routinely divided into two intervals separated by an awake period called the watch

In historical biphasic sleep, individuals slept for roughly four hours, stayed awake for several hours, and then slept a second phase

The mammalian hypothalamus contains primitive neural circuits that govern fundamental instinctive drives including mating, feeding, fighting, and fleeing

Alpha-glycerylphosphorylcholine enhances central cholinergic neurotransmission and can increase the proportion of rapid eye movement sleep when taken prior to sleep

Silencing specific prefrontal cortical neural circuits in mice causes previously dominant mice to lose territory battles in the rodent tube test

Experimental optogenetic or electrical activation of prefrontal cortical circuits in mice transforms previously subordinate mice into persistent winners in the tube test

Subjects placed in pre-industrial lighting conditions naturally revert to biphasic sleep patterns

Human circadian rhythm disruptions and continuous daylight exposure severely impair the production of restorative sleep architecture and neurotransmitters regulating motivation

Neurosurgical patients self-stimulating the midline thalamus in Dr. Robert Heath's studies reported feelings of mild frustration and anger that they experienced as highly arousing and motivating

Acute painful stressors trigger the release of epinephrine in the peripheral nervous system and norepinephrine from the locus coeruleus in the brain

Habituation to cold water and severe sleep deprivation can diminish emotional responsiveness to acute physiological stressors during extreme endurance events

In clinical neurosurgical experiments conducted by Dr. Robert Heath, patients with implanted intracranial electrodes most frequently chose to self-stimulate regions of the midline thalamus

In northern Scotland's Pentland Firth, tidal currents can reach speeds of up to 10 knots

Deciduous trees produce their spring buds before their autumn leaves drop off

The University of Iceland partnered with Ross Edgley during his Iceland swim to collect environmental DNA samples to track marine biodiversity

Deciduous trees shed their leaves in winter to conserve energy

When a rabbit runs, its flashing white tail acts as a danger signal that prompts other rabbits to flee

A hibernating dormouse can lower its body temperature to four degrees Celsius

Swimming or fleeing rapidly away from apex predatory sharks triggers predatory pursuit behavior by signaling vulnerability