Seasonal affective disorder (SAD) is a well-known phenomenon, one that disappears on bright days when the sunshine returns. Researchers at the University of Geneva have concluded a study that shows how the brain responds to blue light, a part of the light spectrum that is often in short supply in the winter, particularly in northern Europe. The research found that such ambient blue light, found in daylight, increased responses to the stimuli in the "voice area" of the brain and in the hippocampus, an area of the brain that is important for memory processes. The light also led to a tighter interaction between a part of the brain that regulates emotions and the hypothalamus, which responds to light to regulate biological rhythms.
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