Neuroscience researchers at Michigan State University recently published a study examining how light affects functions of the hippocampus in the brain.  To do this they split a group of diurnal Nile grass rats into two groups.  The first group were exposed to 12 hours of bright light to emulate daytime (1,000 lux) and 12 hours of darkness to emulate night.  The second group were exposed to dim light during ‘daytime’ and darkness during the night hours.

Researchers found that rats exposed to the darker environment lost around 30% capacity of the hippocampus – a region of the brain responsible for learning and memory.  They also exhibited impaired scores on spatial tasks they had previously learned.

The good news is that these losses appear not to be permanent.  Performance of this impaired group improved substantially after four weeks of exposure to the brighter light of the first group.