Related Experiment Video
Updated: Apr 28, 2026

In Vitro Bioluminescence Assay to Characterize Circadian Rhythm in Mammary Epithelial Cells
Published on: September 28, 2017
Light as a central modulator of circadian rhythms, sleep and affect
Tara A LeGates1, Diego C Fernandez2, Samer Hattar3
11] Johns Hopkins University, Department of Biology, Baltimore, Maryland 21218, USA. [2] Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland 21201, USA.
None:
Light has profoundly influenced the evolution of life on earth. As widely appreciated, light enables us to generate images of our environment. However, light - through intrinsically photosensitive retinal ganglion cells (ipRGCs) - also influences behaviours that are essential for our health and quality of life but are independent of image formation. These include the synchronization of the circadian clock to the solar day, tracking of seasonal changes and the regulation of sleep. Irregular light environments lead to problems in circadian rhythms and sleep, which eventually cause mood and learning deficits. Recently, it was found that irregular light can also directly affect mood and learning without producing major disruptions in circadian rhythms and sleep. In this Review, we discuss the indirect and direct influence of light on mood and learning, and provide a model for how light, the circadian clock and sleep interact to influence mood and cognitive functions.
Related Concept Videos
Circadian Rhythms and Gene Regulation
Circadian Rhythms and Gene Regulation
Biological Clocks and Seasonal Responses
Understanding Sleep
The circadian rhythm, a nearly 24-hour cycle, is deeply influenced by environmental light cues. Light exposure directly affects the hypothalamus, which in turn regulates...
Management of Insomnia
The Pineal Gland
The primary secretion of the pineal gland is the hormone melatonin, derived from serotonin. The concentration of melatonin in the...

