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| Name | Class |
|---|---|
| Stanford University | OTHER |
| Palo Alto Veterans Institute for Research | OTHER |
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Light is the primary means by which the internal circadian clock remains aligned ("entrained") with the external world. Misalignment of this internal clock can occur during situations such as shift work and jet travel across multiple time zones (jet lag). The purpose of this study is to examine how sequences of brief flashes of light can affect entrainment of the clock.
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| Label | Type | Description | Intervention Names |
|---|---|---|---|
| Light | Experimental | Sequence of bright light flashes of varying durations, interflash intervals, flash lengths, flash brightness, and flash color. |
|
| Name | Type | Description | Arm Group Labels | Other Names |
|---|---|---|---|---|
| Bright light | Other | Light is administered through a custom designed mask with LED lights. |
|
| Measure | Description | Time Frame |
|---|---|---|
| Circadian phase | The timing of the onset of melatonin is compared before and after a light stimulus | 2 days |
| Measure | Description | Time Frame |
|---|---|---|
| Alertness | Alertness as assessed through change in brain wave (electroencephalographic, EEG) activity, questionnaires, and objective testing is examined before and at the end of a light stimulus | 1 hour |
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Inclusion Criteria:
Exclusion Criteria:
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| Name | Role | Phone | Extension | |
|---|---|---|---|---|
| Marisol Duran | Contact | 650-493-5000 | 61971 | mreinoso@pavir.org |
| Name | Affiliation | Role |
|---|---|---|
| Jamie M Zeitzer, PhD | Stanford University/VAPAHCS | Principal Investigator |
| Facility | Status | City | State | ZIP | Country | Contacts |
|---|---|---|---|---|---|---|
| VA Palo Alto Health Care System | Recruiting | Palo Alto | California | 94304 | United States |
| PubMed Identifier | Type | Citation | Retractions |
|---|---|---|---|
| 10922269 | Background | Zeitzer JM, Dijk DJ, Kronauer R, Brown E, Czeisler C; New Collective Author. Sensitivity of the human circadian pacemaker to nocturnal light: melatonin phase resetting and suppression. J Physiol. 2000 Aug 1;526 Pt 3(Pt 3):695-702. doi: 10.1111/j.1469-7793.2000.00695.x. | |
| 10996410 | Background | Cajochen C, Zeitzer JM, Czeisler CA, Dijk DJ; New Collective Author. Dose-response relationship for light intensity and ocular and electroencephalographic correlates of human alertness. Behav Brain Res. 2000 Oct;115(1):75-83. doi: 10.1016/s0166-4328(00)00236-9. |
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The investigator is unaware of specific sequence of light that is given to the participant until all data are analyzed.
| 15890792 | Background | Zeitzer JM, Khalsa SB, Boivin DB, Duffy JF, Shanahan TL, Kronauer RE, Czeisler CA; New Collective Author. Temporal dynamics of late-night photic stimulation of the human circadian timing system. Am J Physiol Regul Integr Comp Physiol. 2005 Sep;289(3):R839-44. doi: 10.1152/ajpregu.00232.2005. Epub 2005 May 12. |
| 21760955 | Result | Zeitzer JM, Ruby NF, Fisicaro RA, Heller HC. Response of the human circadian system to millisecond flashes of light. PLoS One. 2011;6(7):e22078. doi: 10.1371/journal.pone.0022078. Epub 2011 Jul 8. |
| 25227334 | Result | Zeitzer JM, Fisicaro RA, Ruby NF, Heller HC. Millisecond flashes of light phase delay the human circadian clock during sleep. J Biol Rhythms. 2014 Oct;29(5):370-6. doi: 10.1177/0748730414546532. Epub 2014 Sep 16. |
| 26854928 | Result | Najjar RP, Zeitzer JM. Temporal integration of light flashes by the human circadian system. J Clin Invest. 2016 Mar 1;126(3):938-47. doi: 10.1172/JCI82306. Epub 2016 Feb 8. |
| 35259981 | Result | Joyce DS, Spitschan M, Zeitzer JM. Duration invariance and intensity dependence of the human circadian system phase shifting response to brief light flashes. Proc Biol Sci. 2022 Mar 9;289(1970):20211943. doi: 10.1098/rspb.2021.1943. Epub 2022 Mar 9. |