The Effects of Acute vs. Chronic of Screen Illumination on: Sleep Efficacy and Architecture, Physiology, Emotion and Behavior: Possible Effect on Human Health

The human eye has a dual role, which is reflected by the various photo-receptors used for vision of images and colors ,Image forming photoreceptors (IFP) and for entrainment of our "Biological clock" located in the hypothalamus through the retinal ganglions known as non-image forming photoreceptors (NIFP). The recently discovered new photo-pigment melanopsin which is sensitive to short wavelength (SWL) illumination exists in the-NIFP. The axons of the NIFP form a special nerve known as the Retino-hypothalamic-tract (RHT) that transfers the SWL signal to the biological clock resulting in suppression of pineal melatonin (MLT) production. This is the basic mechanism by which environmental light/dark cycles entrain the biological clock and transfer the message to organs, tissues and cell. The American Medical Association (AMA) issued a resolution in 2012 stating that light at night constitutes environmental pollution because it violates the daily cycles, including the waking and sleeping cycles, and suppresses the secretion of melatonin from the pineal gland at night. Results of other studies have shown that exposure to artificial light at night (ALAN) and mainly those emerging from SWL sources suppresses MLT-produced in the pineal gland. Computers, tablets, TVs, and smart-phones screens emit SWL illumination, during the day and night hours, whether as active or passive users. The results of previous studies show that, exposure to SWL-ALAN illumination suppresses MLT-secretion and disrupts sleep patterns. In order to understand better the effect of SWL-exposure emerging from screens on human behavior and health, the investigators will study the effects of SWL-exposure on the structure and quality of sleep, cognitive functioning in Continous Performance Test (CPT III), emotional state, and physiological, variables (melatonin secretion levels and body temperature) that were not tested in previous studies.