Free-running sleep

Circadian rhythm

Neuroscience

Light effects on circadian rhythm

Dark therapy

Modulation (music)

Operating system

Psychiatry

Alertness

Computer science

Acoustics

Sleep (system call)

Thermodynamics

Sleep deprivation

Physics

Psychology

Circadian clock

Wake

Electroencephalography

Medicine

Mechanics

Wakefulness

Audiology

Clocks & Sleep

Light, through its non-imaging forming effects, plays a dominant role on a myriad of physiological functions, including the human sleep-wake cycle. The non-image forming effects of light heavily rely on specific properties such as intensity, duration, timing, pattern, and wavelengths. Here, we address how specific properties of light influence sleep and wakefulness in humans through acute effects, e.g., on alertness, and/or effects on the circadian timing system. Of critical relevance, we discuss how different characteristics of light exposure across the 24-h day can lead to changes in sleep-wake timing, sleep propensity, sleep architecture, and sleep and wake electroencephalogram (EEG) power spectra. Ultimately, knowledge on how light affects sleep and wakefulness can improve light settings at home and at the workplace to improve health and well-being and optimize treatments of chronobiological disorders.

Light Modulation of Human Clocks, Wake, and Sleep