Slow-Wave Sleep

A Slow-Wave Sleep is a Non-Rapid Eye Movement Sleep that consists of Stage three (combined stages 3 and 4) of non-rapid eye movement sleep.

• AKA: Deep Sleep.
• See: Parasympathetic Nervous System, Non-Rapid Eye Movement Sleep, Delta Wave, American Academy of Sleep Medicine, Electroencephalography, Hertz, Neuron, Neocortex, Rapid Eye Movement Sleep, Memory Consolidation, Sleep Spindle, Growth Hormone.

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References

2018

• (Wikipedia, 2018) ⇒ https://en.wikipedia.org/wiki/Slow-wave_sleep Retrieved:2018-1-16.
  • Slow-wave sleep (SWS), often referred to as deep sleep, consists of Stage three (combined stages 3 and 4) of non-rapid eye movement sleep. Initially, SWS consisted of both Stage 3 (N3), which has 20-50 percent delta wave activity, and Stage four (N4), which has more than 50 percent delta wave activity. However, as of 2008, the American Academy of Sleep Medicine (AASM) has discontinued the use of Stage four as a separate stage. Thus, the two stages are now combined as "Stage three". An epoch (30 seconds of sleep) which consists of 20% or more slow-wave (delta) sleep is now considered to be stage three. This period of sleep is called slow-wave sleep because the EEG activity is synchronized, producing slow waves with a frequency range of 0.5-2 Hz and peak-to-peak amplitude greater than 75µV. The first section of the wave signifies a "down state," which is an inhibition or hyperpolarizing phase in which the neurons in the neocortex are silent. This is the period when the neocortical neurons are able to rest. The second section of the wave signifies an "up state," which is an excitation or depolarizing phase in which the neurons fire briefly at a high rate. The principal characteristics during slow-wave sleep that contrast with REM sleep are moderate muscle tone, slow or absent eye movement, and lack of genital activity. Slow-wave sleep is considered important for memory consolidation. This is sometimes referred to as "sleep-dependent memory processing". Impaired memory consolidation has been seen in individuals with primary insomnia who thus do not perform as well as those who are healthy in memory tasks following a period of sleep. Furthermore, slow-wave sleep improves declarative memory (which includes semantic and episodic memory). A central model has been hypothesized that the long-term memory storage is facilitated by an interaction between the hippocampal and neocortical networks. In several studies, after the subjects have had training to learn a declarative memory task, the density of human sleep spindles present was significantly higher than the signals observed during the control tasks that involved similar visual stimulation and cognitively-demanding tasks but did not require learning. This associated with the spontaneously occurring wave oscillations that account for the intracellular recordings from thalamic and cortical neurons. Sleep deprivation studies with humans suggest that the primary function of slow-wave sleep may be to allow the brain to recover from its daily activities. Glucose metabolism in the brain increases as a result of tasks that demand mental activity. Another function affected by slow-wave sleep is the secretion of growth hormone, which is always greatest during this stage. It is also thought to be responsible for a decrease in sympathetic and increase in parasympathetic neural activity.

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