Hamsters that spent the night in dim blue or white light had a significantly reduced density of dendritic spines compared to those that lived in total darkness or that were exposed to only red light. Those that lived with dim white or blue light at night drank significantly less of the sugar water than the others.Īfter the testing, the researchers then examined the hippocampus regions of the brains of the hamsters. Results showed that hamsters that were kept in the dark at night drank the most sugar water, followed closely by those exposed to red light. For example, if the hamsters drink less-than-normal amounts of sugar water - a treat they normally enjoy - that is seen as evidence of a mood problem. They then did several tests with the hamsters that are used to check for depressive-like symptoms. In one experiment, the researchers exposed adult female Siberian hamsters to four weeks each of nighttime conditions with no light, dim red light, dim white light (similar to that found in normal light bulbs) or dim blue light. "We wanted to see how exposure to these different color wavelengths affected the hamsters." "These cells are most sensitive to blue wavelengths and least sensitive to red wavelengths," Nelson said. The ipRGCs don't appear to react to light of different wavelengths in the same way. What people experience as different colors of light are actually lights of different wavelengths. "This may be why light at night seems to be linked to depression in some people." "Light at night may result in parts of the brain regulating mood receiving signals during times of the day when they shouldn't," said co-author Tracy Bedrosian, a former graduate student at Ohio State who is now a postdoctoral researcher at the Salk Institute. Other research suggests these light-sensitive cells also send messages to parts of the brain that play a role in mood and emotion. This is the body's master clock that helps determine when people feel sleepy and awake. ![]() The research examined the role of specialized photosensitive cells in the retina - called ipRGCs - that don't have a major role in vision, but detect light and send messages to a part of the brain that helps regulate the body's circadian clock. ![]() 7, 2013, issue of The Journal of Neuroscience. "Our findings suggest that if we could use red light when appropriate for night-shift workers, it may not have some of the negative effects on their health that white light does," Nelson said. The findings may have important implications for humans, particularly those whose work on night shifts makes them susceptible to mood disorders, said Randy Nelson, co-author of the study and professor of neuroscience and psychology at The Ohio State University. The only hamsters that fared better than those exposed to red light were those that had total darkness at night. In a study involving hamsters, researchers found that blue light had the worst effects on mood-related measures, followed closely by white light.īut hamsters exposed to red light at night had significantly less evidence of depressive-like symptoms and changes in the brain linked to depression, compared to those that experienced blue or white light.
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