Dimmer and Dumber

Too much time in the dark could impact brain function

March 2018

As diurnal beings, light exposure is important. As well as dictating circadian rhythm, it also impacts other processes, such as wakefulness or mood. But does it also affect brain function during tasks? Research from a team of neuroscientists suggests that insufficient exposure to bright light could impact brain structure and function. The group from Michigan State University, East Lansing, USA, studied how bright and dim light affects hippocampal function in Nile grass rats (which are diurnal, like humans) (1). Following four weeks of exposure to dim light, the rats showed cognitive and behavioral changes, including impairments in spatial memory. Furthermore, hippocampal expression of brain-derived neurotrophic factor was reduced, and there was a 30 percent decrease in dendritic connections in the hippocampus (Figure 1). Impairments in functioning and changes in hippocampal structure were reversed after four weeks exposure to bright light.