Research with rats confirms that being in dim light may not be good for our cognitive performance (“Does Dim Light Make Us Dumber,” 2018). Previous research has linked brighter light with improved “cognitive performance in school children, healthy adults, and patients in early stages of dementia” (Soler, Robison, Nunez, and Yan, in press). The Michigan State press release states that “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.” It reports that the Soler lead team “studied the brains of . . . rats . . . 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 . . . showed significant improvement on the spatial task. . . . 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. . . is the first to show that changes in environmental light, in a range normally experienced by humans, leads to structural changes in the brain.” The light levels experienced by the test rats are reported in Hippocampus, but the usefulness of reproducing the exact lighting levels tested on the rats in offices, etc., has yet to be established. Soler and colleagues exposed rats to light levels of 1,000 lux or 50 lux for 12 hours at a time, with dark periods between the lighted ones.
Joel Soler, Alfred Robison, Antonio Nunez, and Lily Yan. “Light Modulates Hippocampal Function and Spatial Learning in a Diurnal Rodent Species: A Study Using Male Nile Grass Rat (Arvicanthis Niloticus).” Hippocampus, in press.
“Does Dim Light Make Us Dumber?” 2018. Press release, Michigan State University, http://msutoday.msu.edu/news/2018/does-dim-light-make-us-dumber/.