Neuroscience Breakthroughs Since Graduate School - Part 1: Sleep
Updated: Mar 24
Behavioral neuroscience discoveries have proceeded at a rapid pace. This series highlights cutting-edge findings and explains their importance for neurofeedback providers and their clients. This initial installment focuses on sleep.
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Sleep Architecture Overview
We can divide sleep into non-REM (NREM) sleep which contains three stages, and rapid eye movement (REM) sleep. Stage 3 sleep (NREM3), termed slow-wave sleep and REM sleep, are arguably the most crucial stages. Following total sleep deprivation, we spend more time in Stage 3 on night one and in REM on night two (Breedlove & Watson, 2020). Graphic retrieved from Healing Touch Diagnostics.
An average night’s sleep contains 4-5 cycles, 90-110 minutes each. Adults spend about 20% of total sleep in REM. Early cycles contain more stage 3 slow wave sleep (SWS), while later cycles contain increasing amounts of REM sleep (Breedlove & Watson, 2020). The hormone hypocretin regulates the order of our sleep stages. Excessive hypocretin is associated with insomnia, whereas deficient hypocretin is observed in narcolepsy (Holm et al., 2022). Graphic of a typical night of young adult sleep © Oxford University Press.
Why Is SWS Important?
SWS performs four functions vital to brain health and performance: growth hormone release, glymphatic system waste removal, replenishing astrocyte glycogen stores, and consolidating memory.
Growth Hormone Release
The body releases most growth hormone (GH; somatotropin) during SWS in the first half of the night. GH promotes bodywide tissue growth and repair by influencing protein metabolism (Breedlove & Watson, 2020). Graphic by Smiley et al. (2019) retrieved from ResearchGate.
At age 60, we spend half the time in stage 3 compared with age 20. Stage 3 sleep disappears by age 90, and its loss may be associated with cognitive impairment. Patients diagnosed with senile dementia spend significantly less time in Stage 3 (Kondratova & Kondratova, 2012). Growth hormone loss due to sleep disruption and the progressive reduction in Stage 3 sleep may cause cognitive deficits. Graphic of elderly sleep © Oxford University Press.