Spending prolonged periods of time under dim light conditions regularly can have an adverse impact on the brain’s capacity to remember, as well as learn new things. This is because spending too much time in dimly lit rooms can change the structure of the brain. This study was funded by the National Institutes of Health and was published in the journal Hippocampus.

In this study, scientists studied the effect of dim light on the brains of Nile grass rats. These rats were used in the experiments because they are diurnal creatures – meaning that they stay awake during the day and sleep at night. These rats were exposed to dim and bright lights for 4 weeks.

The rats which were exposed to dim lights showed a 30% decrease in the capacity of the hippocampus, which is the region of the brain used for memory and learning. Moreover, when tested to perform a task they were trained to do previously, these rats didn’t perform well. The other group of rats which was exposed to bright lights was able to perform better.

However, when the first group of rats which was earlier exposed to dim lights was then exposed to bright lights for some time, they were finally able to do the tasks correctly. “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,” said Antonio “Tony” Nunez, psychology professor and co-investigator on the study. “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.”

This is the first such study which shows the environmental light has the capacity to influence structural changes in the brain. More research is needed in this sector because a research has indicated that Americans spend about 90% of their time indoors – and better lighting conditions are needed to ensure no adverse effect on the brain.


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