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Evaluation of Photic Countermeasures for Circadian Entrainment of Neurobehavioral Performance and Sleep-Wake Regulation Before and during Spaceflight (NCC958HFP01601)
Principal Investigator
Research Area:
Behavior and performance
Species Studied
Scientific Name: Homo sapiens Species: Human

To synchronize astronauts' circadian sleep-wake schedules to variable launch times, timed exposure to bright light and darkness in the crew quarters during the week-long pre-launch quarantine period has been used since 1990. Although successful at circadian entrainment, bright light protocols are complex to administer and astronauts' compliance is compromised because bright light glare compromises computer/television screen visibility, and increased frequency of headaches, irritability, and nausea. Moreover, bright light remains unavailable as an in-flight countermeasure, requiring astronauts to rely upon hypnotics or wake-promoting therapeutics to provide symptomatic relief. Recent advances reveal that the human circadian pacemaker is most sensitive to shorter wavelength light for both phase shifting and direct enhancement of alertness and performance. Investigators found that short-wavelength light (approximately 460nm-512nm) in the blue/green range facilitates circadian phase shifting. Therefore they proposed to test the efficacy of exposure to short wavelength green light at a standard intensity for pre-launch and in-flight phase shifting.

The investigators tested the circadian phase-shifting efficacy of exposure to short wavelength light throughout scheduled wake times on a protocol designed to simulate the schedule of crewmembers during the pre-launch quarantine period on a mission that required an eight-hour phase advance of the sleep-wake schedule. Their goal was to demonstrate that exposure to ambient short wavelength fluorescent light will synchronize human circadian rhythms to a shifted sleep/wake schedule within four to five days, enhancing alertness and performance during the biological night.

Specific Aims:

  1. Exposure to ambient polychromatic short wavelength light from fluorescent lamps will be more effective than exposure to an equal illuminance of ambient polychromatic white light from standard fluorescent lamps in shifting the circadian rhythms of test subjects, as measured by dim-light melatonin onset (DLMO), in response to both a gradual 8-hour advance and to an abrupt shift of their sleep-wake schedule.
  2. Alertness and neurobehavioral performance in dim light on a constant routine during times at which crewmembers should be awake on the simulated mission will be significantly greater following four to five days of exposure to ambient polychromatic green light versus ambient white light of equal illuminance, due to more effective circadian entrainment.
  3. Alertness and neurobehavioral performance will be significantly better on the first night of exposure to ambient polychromatic short wavelength light vs. ambient white light of equal illuminance, prior to the induced circadian phase shifts, due to the immediate alerting effects of exposure to ambient polychromatic short wavelength light.
  4. Sleep efficiency and total sleep time will be significantly increased and latency to persistent sleep and wake time after sleep onset will be significantly decreased during the sleep episode following four to five days of exposure to ambient polychromatic green light versus ambient white light of equal illuminance, due to more effective circadian entrainment.

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Chang AM, Scheer FA, and Czeisler CA. The human circadian system adapts to prior photic history. Journal of Physiology.2011. March 1; 589(Pt 5):1095-102. []

Chang AM, Scheer FA, Czeisler CA, and Aeschbach D. Direct effects of light on alertness, vigilance, and the waking electroencephalogram in humans depend on prior light history. Sleep. 2013. August 1; 36(8):1239-46. []

Dijk DJ1, Duffy JF, Silva EJ, Shanahan TL, Boivin DB, and Czeisler CA. Amplitude reduction and phase shifts of melatonin, cortisol and other circadian rhythms after a gradual advance of sleep and light exposure in humans. PLoS One. 2012;7(2):e30037. []

Gooley JJ1, Rajaratnam SM, Brainard GC, Kronauer RE, Czeisler CA, and Lockley SW. Spectral responses of the human circadian system depend on the irradiance and duration of exposure to light. Science Translational Medicine. 2010. May 12; 2(31):31ra33. []

Pomplun M, Silva EJ, Ronda JM, Cain SW, Münch MY, Czeisler CA, and Duffy JF. The effects of circadian phase, time awake, and imposed sleep restriction on performing complex visual tasks: evidence from comparative visual search. Journal of Vision. 2012. July 26; 12(7). []

Rüger M, St Hilaire MA, Brainard GC, Khalsa SB, Kronauer RE, Czeisler CA, and Lockley SW. Human phase response curve to a single 6.5 h pulse of short-wavelength light. Journal of Physiology. 2013. January 1; 591(Pt 1):353-63. []

St Hilaire MA1, Gooley JJ, Khalsa SB, Kronauer RE, Czeisler CA, and Lockley SW. Human phase response curve to a 1 h pulse of bright white light. Journal of Physiology. 2012. July 1; 590(Pt 13):3035-45. []

Wright KP Jr, Drake AL, Frey DJ, Fleshner M, Desouza CA, Gronfier C, and Czeisler CA. Influence of sleep deprivation and circadian misalignment on cortisol, inflammatory markers, and cytokine balance. Brain, Behavior, and Immunity. 2015; Jan 29. []

Circadian rhythm

Data Information
Data Availability
Archive is complete. No data sets are available for this experiment. Please Contact LSDA if you know of available data for this investigation.

Dim light melatonin onset
Latency to persistent sleep time
Neurobehavioral performance
Sleep efficiency
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Mission/Study Information
Mission Launch/Start Date Landing/End Date Duration
Ground 05/01/2009 In Progress

Human Research Program (HRP) Human Research Roadmap (HRR) Information
Crew health and performance is critical to successful human exploration beyond low Earth orbit. The Human Research Program (HRP) investigates and mitigates the highest risks to human health and performance, providing essential countermeasures and technologies for human space exploration. Risks include physiological and performance effects from hazards such as radiation, altered gravity, and hostile environments, as well as unique challenges in medical support, human factors, and behavioral health support. The HRP utilizes an Integrated Research Plan (IRP) to identify the approach and research activities planned to address these risks, which are assigned to specific Elements within the program. The Human Research Roadmap is the web-based tool for communicating the IRP content.

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Additional Information
Managing NASA Center
National Space Biomedical Research Institute (NSBRI)
Responsible NASA Representative
Johnson Space Center LSDA Office
Project Manager: Pamela A. Bieri
Institutional Support
National Space Biomedical Research Institute (NSBRI)
Proposal Date
Proposal Source