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Sleep-Wake Cycles

Sleep-Wake Cycles

Sleep is an essential physiological process vital to maintaining overall well-being. The reticular activating system (RAS), a network of neurons in the brainstem, regulates wakefulness and sleep. While it may seem passive, sleep consists of distinct cycles, each with its unique characteristics and functions. Two key sleep phases are non-rapid eye movement (NREM) and rapid eye movement (REM).
NREM Sleep
NREM sleep comprises four progressive stages that seamlessly merge:

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Related Experiment Video

Updated: Aug 7, 2025

Quantifying Infra-slow Dynamics of Spectral Power and Heart Rate in Sleeping Mice

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Sleep/wake changes in perturbational complexity in rats and mice.

Matias Lorenzo Cavelli^1,2, Rong Mao^1,3, Graham Findlay^1,3

¹Department of Psychiatry, University of Wisconsin-Madison, Madison, WI 53719, USA.

|March 10, 2023

Summary

The Perturbational Complexity Index (PCI^st) reliably measures vigilance states in animals. This index is lower during sleep and anesthesia, correlating with neuronal silence and disrupted network interactions.

Keywords:

Biological sciences Natural sciences Neuroscience

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Last Updated: Aug 7, 2025

Quantifying Infra-slow Dynamics of Spectral Power and Heart Rate in Sleeping Mice

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Published on: August 2, 2017

Polygraphic Recording Procedure for Measuring Sleep in Mice

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Published on: January 25, 2016

Optogenetic Manipulation of Neural Circuits During Monitoring Sleep/wakefulness States in Mice

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Published on: June 19, 2019

Area of Science:

Neuroscience
Computational Neuroscience

Background:

Consciousness assessment in humans relies on spatiotemporal cortical complexity quantified by Perturbational Complexity Index (PCI) and PCI^st (state transitions).
Validating these measures in animal models is crucial for understanding consciousness across species.

Purpose of the Study:

To validate PCI^st as a measure of vigilance states in freely moving rats and mice.
To investigate the relationship between PCI^st, neuronal activity patterns, and cortical stimulation depth.

Main Methods:

Quantified spatiotemporal complexity of cortical responses using PCI^st in rats and mice during various vigilance states (wake, REM sleep, NREM sleep, anesthesia).
Assessed the association between low PCI^st and neuronal silence (OFF periods).
Investigated the effect of deep vs. superficial cortical stimulation on PCI^st.

Main Results:

PCI^st was significantly lower in NREM sleep and slow-wave anesthesia compared to wakefulness or REM sleep, mirroring human findings.
Low PCI^st correlated with the occurrence of neuronal OFF periods.
Stimulation of deep cortical layers reliably altered PCI^st across states, unlike superficial stimulation.
PCI^st changes were consistent across different stimulation/recording sites, with an exception in mouse prefrontal cortex.

Conclusions:

PCI^st reliably measures vigilance states in non-responsive animals.
The findings support the hypothesis that low PCI^st reflects disrupted causal interactions in cortical networks due to neuronal silence (OFF periods).
Deep cortical layer stimulation is key for eliciting reliable PCI^st changes, highlighting the importance of network depth in consciousness.