Circadian timekeeping can be reset by brief flashes of light using stimulation protocols thousands of times shorter than those previously assumed to be necessary for traditional phototherapy. These observations point to a future where flexible architectures of nanosecond-, microsecond-, and millisecond-scale light pulses are compiled to reprogram the brain's internal clock when it has been altered by psychiatric illness or advanced age. In the current review, we present a chronology of seminal experiments that established the synchronizing influence of light on the human circadian system and the efficacy of prolonged bright-light exposure for reducing symptoms associated with seasonal affective disorder. We conclude with a discussion of the different ways that precision flashes could be parlayed during sleep to effect neuroadaptive changes in brain function. This article is a contribution to a special issue on Circadian Rhythms in Regulation of Brain Processes and Role in Psychiatric Disorders curated by editors Shimon Amir, Karen Gamble, Oliver Stork, and Harry Pantazopoulos.
Pancreatic secretion obtained by endoscopic cannulation of the main pancreatic duct and secretin release after duodenal acidification in man
Nocturnal elevation of plasma melatonin and urinary 5-hydroxyindoleacetic acid in young men: attempts at modification by brief changes in environmental lighting and sleep and by autonomic drugs
N-methyl-D-aspartate receptor participates in neuronal transmission of photic information through the retinohypothalamic tract
Sensitivity and integration in a visual pathway for circadian entrainment in the hamster (Mesocricetus auratus)
Phototherapy of seasonal affective disorder. Time of day and suppression of melatonin are not critical for antidepressant effects
Light flashes of different durations (0.063-3.33 msec) phase shift the circadian flight activity of a bat
Relationship between environmental light intensity and retina-mediated suppression of rat pineal serotonin-N-acetyl-transferase
Lesions of the paraventricular nucleus area of the hypothalamus disrupt the suprachiasmatic leads to spinal cord circuit in the melatonin rhythm generating system
Seasonal affective disorder. A description of the syndrome and preliminary findings with light therapy
Spectral sensitivity of a novel photoreceptive system mediating entrainment of mammalian circadian rhythms
A controlled trial of timed bright light and negative air ionization for treatment of winter depression
Distinctiveness and correlates of maladaptive behaviour in children and adolescents with Smith-Magenis syndrome
GABA release from suprachiasmatic nucleus terminals is necessary for the light-induced inhibition of nocturnal melatonin release in the rat
More than a marker: interaction between the circadian regulation of temperature and sleep, age-related changes, and treatment possibilities
Sensitivity of the human circadian pacemaker to nocturnal light: melatonin phase resetting and suppression
An action spectrum for melatonin suppression: evidence for a novel non-rod, non-cone photoreceptor system in humans
The efficacy of light therapy in the treatment of mood disorders: a review and meta-analysis of the evidence
The Can-SAD study: a randomized controlled trial of the effectiveness of light therapy and fluoxetine in patients with winter seasonal affective disorder
Dim light melatonin onset (DLMO): a tool for the analysis of circadian phase in human sleep and chronobiological disorders
Controlled trial of naturalistic dawn simulation and negative air ionization for seasonal affective disorder
Absence of normal photic integration in the circadian visual system: response to millisecond light flashes
Light room therapy effective in mild forms of seasonal affective disorder--a randomised controlled study
The mammalian circadian timing system: organization and coordination of central and peripheral clocks
Low-intensity blue-enriched white light (750 lux) and standard bright light (10,000 lux) are equally effective in treating SAD. A randomized controlled study
The effects of blue-enriched light treatment compared to standard light treatment in Seasonal Affective Disorder
Light therapy for improving cognition, activities of daily living, sleep, challenging behaviour, and psychiatric disturbances in dementia
Limbic thalamus and state-dependent behavior: The paraventricular nucleus of the thalamic midline as a node in circadian timing and sleep/wake-regulatory networks
Outcomes One and Two Winters Following Cognitive-Behavioral Therapy or Light Therapy for Seasonal Affective Disorder
Characterisation of light responses in the retina of mice lacking principle components of rod, cone and melanopsin phototransduction signalling pathways
Cycles of circadian illuminance are sufficient to entrain and maintain circadian locomotor rhythms in Drosophila
Timed Light Therapy for Sleep and Daytime Sleepiness Associated With Parkinson Disease: A Randomized Clinical Trial
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