|   | 
Details
   web
Records
Author (up) Figueiro, M.G.; Bierman, A.; Plitnick, B.; Rea, M.S.
Title Preliminary evidence that both blue and red light can induce alertness at night Type Journal Article
Year 2009 Publication BMC Neuroscience Abbreviated Journal BMC Neurosci
Volume 10 Issue Pages 105
Keywords Adult; Alpha Rhythm; Analysis of Variance; Beta Rhythm; Circadian Rhythm/*physiology; Cornea/physiology; Dose-Response Relationship, Radiation; Electrocardiography; Female; Humans; *Light; Male; Melatonin/secretion; Middle Aged; *Photic Stimulation; Psychomotor Performance; Radioimmunoassay; Salivary Glands/secretion; Wakefulness/*physiology; physiology of vision; blue light; red light
Abstract BACKGROUND: A variety of studies have demonstrated that retinal light exposure can increase alertness at night. It is now well accepted that the circadian system is maximally sensitive to short-wavelength (blue) light and is quite insensitive to long-wavelength (red) light. Retinal exposures to blue light at night have been recently shown to impact alertness, implicating participation by the circadian system. The present experiment was conducted to look at the impact of both blue and red light at two different levels on nocturnal alertness. Visually effective but moderate levels of red light are ineffective for stimulating the circadian system. If it were shown that a moderate level of red light impacts alertness, it would have had to occur via a pathway other than through the circadian system. METHODS: Fourteen subjects participated in a within-subject two-night study, where each participant was exposed to four experimental lighting conditions. Each night each subject was presented a high (40 lx at the cornea) and a low (10 lx at the cornea) diffuse light exposure condition of the same spectrum (blue, lambda(max) = 470 nm, or red, lambda(max) = 630 nm). The presentation order of the light levels was counterbalanced across sessions for a given subject; light spectra were counterbalanced across subjects within sessions. Prior to each lighting condition, subjects remained in the dark (< 1 lx at the cornea) for 60 minutes. Electroencephalogram (EEG) measurements, electrocardiogram (ECG), psychomotor vigilance tests (PVT), self-reports of sleepiness, and saliva samples for melatonin assays were collected at the end of each dark and light periods. RESULTS: Exposures to red and to blue light resulted in increased beta and reduced alpha power relative to preceding dark conditions. Exposures to high, but not low, levels of red and of blue light significantly increased heart rate relative to the dark condition. Performance and sleepiness ratings were not strongly affected by the lighting conditions. Only the higher level of blue light resulted in a reduction in melatonin levels relative to the other lighting conditions. CONCLUSION: These results support previous findings that alertness may be mediated by the circadian system, but it does not seem to be the only light-sensitive pathway that can affect alertness at night.
Address Lighting Research Center, Rensselaer Polytechnic Institute, Troy, NY, USA. figuem@rpi.edu
Corporate Author Thesis
Publisher Place of Publication Editor
Language English Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 1471-2202 ISBN Medium
Area Expedition Conference
Notes PMID:19712442; PMCID:PMC2744917 Approved no
Call Number IDA @ john @ Serial 285
Permanent link to this record
 

 
Author (up) Thorn, L.; Hucklebridge, F.; Esgate, A.; Evans, P.; Clow, A.
Title The effect of dawn simulation on the cortisol response to awakening in healthy participants Type Journal Article
Year 2004 Publication Psychoneuroendocrinology Abbreviated Journal Psychoneuroendocrinology
Volume 29 Issue 7 Pages 925-930
Keywords Human Health; Adult; Affect/*physiology/radiation effects; Arousal/*physiology/radiation effects; Circadian Rhythm/*physiology; Female; Humans; Hydrocortisone/analysis/*physiology/radiation effects; *Light; Male; Middle Aged; Reference Values; Saliva/chemistry; Wakefulness/*physiology/radiation effects
Abstract Bright light exposure after awakening has been shown to elevate cortisol levels in healthy participants. The present study examined the effect of dawn simulation (a treatment for seasonal affective disorder) on the cortisol response to awakening and mood. Twelve healthy participants were supplied with a dawn simulator (The Natural Alarm Clock, Outside In, Cambridge Ltd), a bedside light that increases in intensity prior to awakening to approximately 250 lux over 30 mins when an audible alarm sounds. A counterbalanced study was performed on 4 consecutive normal weekdays, two of which were control days (no dawn simulation) and two experimental (dawn simulation). Saliva samples were taken immediately on awakening then at 15, 30 and 45 minutes post awakening on all 4 study-days. Total cortisol production during the first 45 mins after awakening was found to be significantly higher in the experimental condition than in the control condition. Participants also reported greater arousal in the experimental condition and there was a trend for an association between increased arousal and increased cortisol secretory activity under dawn simulation. This study provides supportive evidence for the role of light and the suprachiasmatic nucleus in the awakening cortisol response.
Address Department of Psychology, University of Westminster, 309 Regent Street, London W1R 8AL, UK
Corporate Author Thesis
Publisher Place of Publication Editor
Language English Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0306-4530 ISBN Medium
Area Expedition Conference
Notes PMID:15177708 Approved no
Call Number LoNNe @ kagoburian @ Serial 824
Permanent link to this record