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Related Experiment Video

Updated: Jun 6, 2026

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

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

Published on: August 2, 2017

A hypothalamic-brainstem activity sequence underlies arousal fluctuations during daytime drowsiness.

Ewa Beldzik^1,2, Nicholas G Cicero^1,2,3,4, Daniel E P Gomez^2,5

¹Institute for Medical Engineering and Sciences, Massachusetts Institute of Technology, Cambridge, MA, USA.

Biorxiv : the Preprint Server for Biology

|June 5, 2026

Summary

Brain activity in arousal-regulating regions fluctuates with drowsiness during monotonous tasks. A specific sequence, led by the hypothalamus, underlies these vigilance changes and impacts brain-wide dynamics.

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Area of Science:

Neuroscience
Cognitive Neuroscience
Sleep Research

Background:

Vigilance and task performance fluctuate during monotonous tasks due to drowsiness.
The role of sleep-wake control circuitry in moment-to-moment arousal fluctuations is not well understood.

Purpose of the Study:

To investigate the subcortical brain activity patterns associated with spontaneous drowsiness during sustained attention.
To determine if sleep-wake control circuitry regulates vigilance fluctuations.

Main Methods:

Utilized high-resolution 7T functional magnetic resonance imaging (fMRI) optimized for subcortical imaging.
Monitored brain activity in arousal regulatory system regions (hypothalamus, brainstem, basal forebrain, thalamus) during a sustained attention task.
Correlated brain activity with spontaneous episodes of drowsiness and behavioral performance changes.

Main Results:

Identified a coordinated activity pattern in arousal-promoting regions (suppression during drowsiness, reactivation during recovery) and the opposite in the sleep-promoting hypothalamic preoptic area.
Observed a consistent ~10-15 second sequence of activity changes, initiated by hypothalamic nuclei.
Found that brainstem nuclei suppression preceded cortical infraslow oscillations, suggesting a role in neurovascular dynamics.

Conclusions:

Drowsiness-related vigilance fluctuations are regulated by a specific, temporally resolved sequence of activity within the human arousal regulatory system.
This sequence is initiated by the hypothalamus and mediated by the brainstem, influencing global cortical hemodynamics.
Provides a network-level understanding of subcortical dynamics during drowsiness.