In this study the investigators plan to systematically characterise infra-slow EEG oscillations during sleep, explore their relationship to the microstructure of sleep, and investigate its role in the physiology and pathophysiology of sleep by co-registration of Full band EEG with polysomnography during wake and sleep in healthy subjects, after sleep deprivation, and in patients with restless legs syndrome/periodic leg movements during sleep (RLS/PLMS).

Sleep is a highly dynamic process and during large parts of sleep the level of arousal fluctuates on a multi-second time scale between the sleep stage specific background and transient, phasic events that clearly arise from this background and constitute the microstructure of sleep. This microstructure is part of the dynamic physiological sleep regulation and at the same time reflects the instability of sleep, is critically involved in the pathophysiology of sleep and a determinant of the recuperative value of sleep and daytime performance.

Intriguingly, these sleep microstructural fluctuations are in a multi-second range that corresponds closely to the so-called infra-slow oscillations that are ubiquitous in the central nervous system. Infra-slow oscillations (0.01 - 0.1 Hz) have been observed in both humans and animals across brain structures and spatial scales in the dynamics of single unit firing rates, direct electrical potential fluctuations and oscillation amplitude modulations. The possibility to record these infra-slow oscillations on the level of the surface EEG with direct current (DC) or Full band (Fb) EEG offers a new approach to study the microstructure of sleep and characterise the full range of sleep-related EEG oscillations.

The objectives of this study are:

1. to record and systematically characterise infra-slow oscillations during wake and all stages of sleep
2. to explore the relationship between sleep infra-slow oscillations and microstructural events of sleep, in particular the cyclic alternating pattern
3. to explore the effect of acute sleep deprivation on sleep infra-slow EEG activity
4. to investigate infra-slow sleep EEG activity in patients with RLS/PLMS, common sleep disorders with prominent periodic arousals, heart rate activations, and leg movements
5. to explore the relationship between infra-slow EEG oscillations and periodic events in movement and autonomic system activity in patients with RLS/PLMS.

Inclusion Criteria for all participants:

• Willingness to participate and written informed consent
• Aged 20 to 40 years at the time of screening
• Body mass index (BMI) ≤ 30

Additional inclusion criteria for subjects with RLS/PLMS:

• Either diagnosis of RLS and current IRLS score ≥ 15.
• Or frequent periodic leg movements during sleep

Exclusion criteria for all participants:

• Pregnancy or breast feeding at the time of screening
• Sleep related breathing disorders
• Current psychiatric disorders
• Current chronic treatment that may affect sleep.
• Any significant neurological disorder or other medical disease that may affect sleep.
• Any unstable medical condition.

Additional exclusion criteria for participants with RLS/PLMS:

• Current intake of dopaminergic drugs
• Current intake of other RLS relevant medication
• Intake of hypnotics
• Other significant sleep disorder except symptoms potentially related to RLS

Additional exclusion criteria for healthy participants:

• Any pharmacological treatment that may affect sleep and/or sleep related movement disorders
• Any clinically significant sleep disorders