The positive effects of bright ambient light are well-known among humans, when it comes to improving cognitive function. A recent study reiterates the point by finding that dim lighting, by contrast, could negatively affect the functioning of the brain among diurnal species — those that are awake through the day and sleep at night — including humans.

Four researchers from Michigan State University (MSU), neuroscientists who authored the study, suggested “spending too much time in dimly lit rooms and offices may actually change the brain’s structure and hurt one’s ability to remember and learn.”

Nile grass rats were chosen as the test subjects for the research because they, like humans, are diurnal. One group of rats was put in low-light conditions and the other in brightly lit environs, each for a period of four weeks. The light was kept on only for 12 hours a day in both cases, with the 12 hours of night being spent in the dark.

“When we exposed the rats to dim light, mimicking the cloudy days of Midwestern winters or typical indoor lighting, the animals showed impairments in spatial learning. This is similar to when people can’t find their way back to their cars in a busy parking lot after spending a few hours in a shopping mall or movie theater,” Antonio Nunez, psychology professor at MSU and co-investigator on the study, said in a statement Monday.

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