Some recent research has found that the right side of the brain is far more active during a nap than the left side, which stays fairly quiet while we’re asleep. Despite the fact that 95% of the population is right-handed, with the left side of their brains being the most dominant, the right side is consistently the more active hemisphere during sleep.
The study’s author, Andrei Medvedev, speculated that the right side of the brain handles ‘housekeeping’ duties while we’re asleep. The study looked at how active various parts of the brain were while participants were sleeping:
Medvedev and his colleagues used a type of brain imaging known as near-infrared spectroscopy, which involves placing optical fibers similar to electrodes symmetrically around a person’s scalp. These “optodes” send infrared light through the brain and measure how much light returns.
The intensity of light bouncing back provides an estimate of the blood flow in different regions of the brain. Blood flow, in turn, is an indicator of how active those regions are.
So while the left side of your brain takes some time off to relax, the right side is clearing out your temporary storage areas, pushing information into long-term storage, and solidifying your memories from the day.