The brain is never truly dormant during your sleep
In short: For decades, sleep was viewed as a period of biological inactivity. However, the advent of EEG recordings in the 1950s revealed a far more complex reality. Your brain remains remarkably active, cycling through distinct electrical patterns that distinguish deep rest from the vivid, paradoxical states of dreaming.
The study of sleep faced significant hurdles until the 1950s because researchers could not easily observe internal processes in recumbent subjects, and self-reported questionnaires were unreliable due to poor memory. The breakthrough came with EEG technology, which allowed scientists to map brain electrical activity, or "brain waves." While awake, humans typically exhibit a regular alpha rhythm of approximately 10 cycles per second (cps). As sleep begins, these waves slow down and become less regular, marking the onset of orthodox sleep. However, after about one hour, the brain enters a state known as paradoxical sleep. During this phase, the brain is highly active despite low muscle tone. This state is also characterized by rapid eye movements (REM), which occur under closed eyelids. REM sleep is not universal across the animal kingdom; it is absent in reptiles and appears only briefly in birds, though it is prominent in mammals—particularly predators. The distribution of REM sleep varies significantly by age: it constitutes about half of a newborn infant's sleep, more than a quarter of an adult's sleep, and begins in the fetus around 30 weeks into pregnancy. Understanding these cycles is vital because sleep deprivation leads to a rapid deterioration in performance, specifically regarding sustained concentration. Prolonged deprivation can cause behavior to become shambolic, leading to irritability, incoherence, and eventually delusions or hallucinations. These physiological vulnerabilities have even been exploited historically as a method of persuasion in interrogation settings.
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Sources
- Summary by Intellect · source: Sleep and Dreams - Professor Glenn D Wilson
- Also: Sleep and Dreams
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