This symposium was presented in person at World Sleep 2025 in Singapore.

To access the session recording, navigate to the content tab and click the view video button. 

Session Schedule

Find a specific presentation in the course by navigating to the timestamp indicated below.

0:00:00
Introduction

0:05:55
Waves of arousal in health and disease
Aurelie Stephan (France)

0:24:30
Do micro-arousals contribute to the restorative property of sleep?
Natalie Hauglund (Denmark)

0:43:25
Bridging developmental and clinical perspectives: The Infraslow fluctuation of sigma power in sleep
Maria Dimitriades (Greece)

1:01:30
To wake or continue sleep: Arousal characteristics in adults with insomnia disorder treated with cannabinoids and placebo
Rick Wassing (Australia)

Summary

Sleep instability is a hallmark of many wake and sleep-related disorders, including sleep apnea [1], insomnia [2], dementia [3], and schizophrenia [4]. Recent studies have discovered how the dynamics of the ascending reticular arousal system during sleep regulate sleep stability [5-8], which relates to known sleep disturbances and next-day consequences in the mentioned populations. By integrating findings from animal models, human developmental studies, and clinical research, this symposium explores how fundamental sleep mechanisms interact with arousals to regulate the stability of sleep, how this links with sleep functions, and how these mechanisms may be disturbed in sleep disorders. The symposium includes four early career and young investigators’ presentations, followed by a panel discussion. It will foster a deeper cross-disciplinary understanding of the interplay between sleep microarchitecture and arousal, offering insights into novel therapeutic and diagnostic avenues.

The first talk will set the stage by describing the continuum between normal awakenings and pathological sleep disruptions. By examining innovative EEG markers of sleep arousal, it will provide a nuanced understanding of how wake-like activity intrudes on normal sleep and sleep disorders, particularly insomnia, sleep misperception, and NREM parasomnias.

The second talk delves into the fundamental role of arousals in restorative sleep functions. It will present rodent studies showing that the homeostatic increase in NREM slow wave activity after sleep deprivation is most pronounced immediately after arousals and that arousals are linked to glymphatic clearance of metabolites from the brain. These findings establish arousals as pivotal to maintaining brain health.

Transitioning from general sleep disruptions, the third presentation will focus on the links between arousals and infraslow fluctuations of sigma power (ISFS) during NREM sleep across human development. Findings from acoustic stimulation experiments in healthy adults will further show the interaction between sleep stability and arousal mechanisms in response to external stimuli. Finally, this presentation will end with a description of ISFS in young individuals with schizophrenia.

The final presentation will expand on these clinical perspectives by showing how cannabinoids modulate arousals and the ISFS using data from a placebo-controlled clinical trial in insomnia. This talk will discuss how arousal severity and the phase angle of the ISFS can influence sleep-state changes and how cannabinoid treatments may exacerbate this instability. These insights highlight the potential of arousal characteristics as clinical markers and their relevance for addressing the consequences of insomnia.

The final part of the symposium is a panel discussion, during which the chairs will prepare questions for the four presenters on the relevance of this emerging area of sleep neuroscience and its potential impact on clinical practice in the next decade and open the floor for questions.