Bright light resets the human circadian pacemaker independent of the timing of the sleep-wake cycle.

  title={Bright light resets the human circadian pacemaker independent of the timing of the sleep-wake cycle.},
  author={Charles A. Czeisler and James S. Allan and Steven H. Strogatz and Joseph M. Ronda and R S{\'a}nchez and C. D R{\'i}os and W O Freitag and Gary S. Richardson and Richard E. Kronauer},
  volume={233 4764},
Human circadian rhythms were once thought to be insensitive to light, with synchronization to the 24-hour day accomplished either through social contacts or the sleep-wake schedule. Yet the demonstration of an intensity-dependent neuroendocrine response to bright light has led to renewed consideration of light as a possible synchronizer of the human circadian pacemaker. In a laboratory study, the output of the circadian pacemaker of an elderly woman was monitored before and after exposure to 4… 

The effect of light on the human circadian pacemaker.

Exposure to a cyclic light stimulus can induce strong (type 0) resetting of the human circadian pacemaker, indicating that exposure to light affects the pacemaker's amplitude of oscillation as well as its phase.

Melatonin Rhythm Observed throughout a Three-Cycle Bright-Light Stimulus Designed to Reset the Human Circadian Pacemaker

Observation of the melatonin rhythm throughout a three-cycle resetting trial has provided a dynamic view of the daily phase-resetting response of the human circadian pacemaker, confirming the importance of considering both phase and amplitude when describing the resetting of thehuman circadianpacemaker by light.

Circadian Phase Resetting in Older People by Ocular Bright Light Exposure

The maintained responsiveness of the circadian pacemaker to light implies that scheduled bright light exposure can be used to treat circadian phase disturbances in older people.

Temporal dynamics of late-night photic stimulation of the human circadian timing system.

The data indicate that the human circadian pacemaker is highly sensitive even to typical room light intensities during the late biological night, with approximately 100 lux evoking half of the effects observed with light 10 times as bright.

Sensitivity of the Human Circadian Pacemaker to Moderately Bright Light

The hypothesis that the phase-shifting effect of light on the human circadian pacemaker has a strongly nonlinear relationship to illuminance levels, such that it is preserved despite marked reductions in light intensity is supported.

Light exposure induces equivalent phase shifts of the endogenous circadian rhythms of circulating plasma melatonin and core body temperature in men.

Using the time of the fitted temperature minimum as a reference standard, the fitted maximum of the endogenous 24-h melatonin profile was a more reliable phase marker than the onset of the nocturnal rise of melatonin.

Bright light induction of strong (type 0) resetting of the human circadian pacemaker.

The data indicate that the sensitivity of the human circadian pacemaker to light is far greater than previously recognized and have important implications for the therapeutic use of light in the management of disorders of circadian regulation.

The acute and phase-shifting effects of artificial bright light on human physiology, performance and symptoms of jet-lag

The periodic alternation of light and darkness over the solar day has a fundamental role in synchronising human circadian rhythms. Artificial light is known to alter circadian timing depending on

Bright morning light advances the human circadian system without affecting NREM sleep homeostasis.

Spectral analysis of the sleep electroencephalogram (EEG) revealed that the advance of the circadian pacemaker did not affect EEG power densities between 0.25 and 15.0 Hz during either non-REM or REM sleep.

Use of Light to Treat Jet Lag: Differential Effects of Normal and Bright Artificial Light on Human Circadian Rhythms

  • Psychology
    Annals of the New York Academy of Sciences
  • 1985
The endogenously generated circadian rhythmicity is modified by special exogenous stimuli and, in most animal circadian rhythms, light is the most effective external stimulus.

Circadian regulation dominates homeostatic control of sleep length and prior wake length in humans.

It is reported that there is no significant positive correlation between the residuals of alpha and rho, contrary to the prediction of restorative models of sleep duration and much-needed tests of mathematical models of the sleep-wake cycle.


It is found that the cyclic alternation of light and dark, when applied to human subjects in a comparable way to experiments in other species, was an effective entraining agent and a critical review of the literature indicate that a LD cycle alone can be an effective environmental synchronizer of the human circadian timing system.

Human sleep: its duration and organization depend on its circadian phase.

Two- to threefold variations in sleep length were observed in 12 subjects living on self-selected schedules in an environment free of time cues. The duration of polygraphically recorded sleep

Human Circadian Rhythms in Continuous Darkness: Entrainment by Social Cues

Social cues are sufficient to entrain human circadian rhythms, and absence of light has no immediate effect on the functions measured.

Therapeutic Effects of Bright Light in Depressed Patients a

  • Psychology
    Annals of the New York Academy of Sciences
  • 1985
Over the ensuing years, many observations have tended to confirm both chronobiologic and photoperiodic elements in depression, but expanding data suggest much complexity that defies any simple chronobiological hypothesis.

Daily light sensitivity rhythm in a rodent.

A daily rhythm of sensitivity to these standard light periods was found in flying squirrels otherwise maintained in constant darkness.

Light suppresses melatonin secretion in humans.

Findings establish that the human response to light is qualitatively similar to that of other mammals.