Dim lights might make us less bright.

Science Daily turns the lights up on Michigan State University neurological research showing sitting in a darkened room can hurt the brain’s ability to remember and learn:

The researchers studied the brains of Nile grass rats (which, like humans, are diurnal and sleep at night) after exposing them to dim and bright light for four weeks. The rodents exposed to dim light lost about 30 percent of capacity in the hippocampus, a critical brain region for learning and memory, and performed poorly on a spatial task they had trained on previously.

The rats exposed to bright light, on the other hand, showed significant improvement on the spatial task. Further, when the rodents that had been exposed to dim light were then exposed to bright light for four weeks (after a month-long break), their brain capacity — and performance on the task — recovered fully.

The study, funded by the National Institutes of Health, is the first to show that changes in environmental light, in a range normally experienced by humans, leads to structural changes in the brain.

[Lily] Yan said the research team is investigating one potential site in the rodents’ brains — a group of neurons in the hypothalamus that produce a peptide called orexin that’s known to influence a variety of brain functions. One of their major research questions: If orexin is given to the rats that are exposed to dim light, will their brains recover without being re-exposed to bright light?