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Slow-wave sleep

Slow-Wave Sleep Overview: – Slow-wave sleep (SWS) is the third stage of non-rapid eye movement sleep (NREM). – SWS is characterized by slow delta waves […]

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Slow-Wave Sleep Overview:
Slow-wave sleep (SWS) is the third stage of non-rapid eye movement sleep (NREM).
– SWS is characterized by slow delta waves on EEG and typically lasts 70-90 minutes in the early part of the night.
– It involves moderate muscle tone, slow or absent eye movement, and lack of genital activity.
– SWS is crucial for memory consolidation, brain recovery, and sleep-dependent memory processing.

Electroencephalographic Characteristics of Slow-Wave Sleep:
– EEG activity in SWS shows slow waves with a frequency range of 0.5–4.5 Hz and a peak-to-peak amplitude greater than 75µV.
– Slow waves consist of down and up states reflecting neuron activity.
– SWS is defined by the presence of 20% delta waves in a 30-second epoch on EEG.
– Longer SWS periods occur mainly in the first two sleep cycles, with children and young adults having more total SWS compared to older adults.

Functions and Importance of Slow-Wave Sleep:
– SWS is vital for memory consolidation, enhances declarative memory, and facilitates long-term memory storage.
– It plays a role in spatial declarative memory, emotional memory consolidation, and synaptic homeostasis.
– Growth hormone secretion is highest during SWS, and it leads to a decrease in sympathetic and an increase in parasympathetic neural activity.
– Slow-wave sleep is essential for physical healing, growth, and learning, including synaptic plasticity and homeostasis.

Factors Affecting Slow-Wave Sleep and Health Impact:
– Individual differences in SWS exist, influenced by factors like gender, age, and heredity.
– Reduced SWS is associated with high cerebrospinal fluid Aβ42 levels and disruption of slow-wave sleep can increase amyloid-β levels.
– Slow-wave sleep is a promising target for Alzheimer’s disease intervention, with sleep disturbances observed in the disease.
– Predictors of slow-wave sleep vary, with age-related reductions noted, and sex and age influencing slow-wave activity in NREM sleep.

Neural Control, Brain Activity, and Research on Slow-Wave Sleep:
– Acetylcholine, norepinephrine, serotonin, histamine, and orexin are involved in sleep patterns, with neocortical neurons firing during SWS.
– Slow-wave sleep is associated with strengthening spatial memories, neuronal plasticity, and seizure prevention.
– Research focuses on memory consolidation, sleep spindles, cellular mechanisms, and the functional topography of nonREM sleep EEG.
– Various brain regions, including the parafacial zone, nucleus accumbens, and lateral hypothalamus, play roles in inducing and regulating slow-wave sleep.

Slow-wave sleep (Wikipedia)

Slow-wave sleep (SWS), often referred to as deep sleep, is the third stage of non-rapid eye movement sleep (NREM), where electroencephalography activity is characterised by slow delta waves.

Ostriches sleeping, with REM and slow-wave sleep phases

Slow-wave sleep usually lasts between 70 and 90 minutes, taking place during the first hours of the night. SWS is characterised by moderate muscle tone, slow or absent eye movement, and lack of genital activity. Slow-wave sleep is considered important for memory consolidation, declarative memory, and the recovery of the brain from daily activities.

Prior to 2007, the term SWS referred to both the third and fourth stages of NREM. However, after both stages were combined into stage three, SWS refers only to the third stage.

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