top of page

Neuroscience Breakthroughs Since Graduate School - Part 1: Sleep

Updated: Mar 24


Hippocampal Neurons

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.


Click on our narrator icon to listen to this post.



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.


Sleep Study


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.


Typical Night of Young Adult Sleep


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.


Elderly Sleep


Glymphatic System Waste Removal