This short article mainly covers the EEG aspects of sleep to familiarize the reader with terminology and specific characteristics of various sleep stages. Learning, behavior, and cognitive performance are improved after sleep, as evidenced by functional magnetic resonance imaging on the visuomotor task performance after normal sleep. Researchers also think that sleep brings about memory consolidation and the plasticity of the cognitive neural networks. There are cross pathways of circadian rhythms and energy metabolism however, during REM sleep, there is increased whole-body oxygen consumption. There are theories on energy conservation to reduce energy expenditure by lowering metabolism and thermoregulation through hypothalamic nuclei. However, researchers generally agree that there are beneficial effects on neuronal function and behavior. There are contradictory findings on the restorative effects of post-exercise sleep–molecular studies on the cell division and DNA transcription function relative to circadian rhythms on various tissues. This includes the early theory of restorative function, which involves the growth and changes in metabolism. There are many theories on the functions of sleep, even though specific research has not validated these. Subsequent developments in this field were carried out by Bremer, Moruzzi, and Kleitman, whose works recognized that sleep is an active, life-supporting process contrary to the long-held belief that sleep is simply a passive process. Lucretius, as early as the first century BCE, described the deafferentation theory of sleep ) the same was revived in the early 19th century by Macnish (Macnish, 1830) and Purkinje. The Hippocratic school (400 BCE) had understood the role of sleep in promoting good health. The Upanishads (approximately 1000 BCE) have described the different states of consciousness. Different states of vigilance like waking and sleep states with or without dreams have been identified since ancient times.

Epilepsy sleep eeg vs normal sleep eeg