Over the years, scientists have studied sleep and have tried to find its purpose. Some believe that we use sleep to conserve much needed energy. Others say that it is an opportunity for the brain to clear away cellular waste. Researchers have even tried to prove that sleep is an evolved method of self protection, in which the animal is forced to lie still and hide itself from predators. However, recently scientists have produced research that concludes the purpose of sleep is to forget some of the things we learn each day.

Learning occurs in the brain when connections are made between neurons. The connections allow for data and information to quickly pass through the brain and create networks. Memories, new ideas, and learned information are stored in these networks. This process is called synapses, and researchers suggest that during the day synapses grow abundantly as we encounter new experiences and our brain circuits become “noisy.” In order to clear this noise our brains use sleep.

In essence, our brains are cleaning up, pruning, and organizing all the information we acquired in one day by cutting certain neuronic connections that are a waste of space. Most of this condensing occurs during deep rapid eye movement (REM) sleep, when the electric brain waves slow down and the brain can stop processing, thinking, and decision making which take up a lot of its energy.

A study completed at Johns Hopkins University proved this theory. The researchers used a chemical that made the protein in mouse brain synapses glow green. They found that the amount of glowing synapses greatly decreased while the mouse was sleeping, because its brain was reducing connections and throwing out unnecessary information. They also discovered and observed an interesting protein called Homer1A.

Homer1A is an essential protein in organizing synapses and information in neurons. In order to test if this protein is important in sleep, the research team genetically engineered mice so that they did not have the ability to produce Homer1A in their brains. They observed that while sleeping, the regular mice and engineered mice slept the same. But, the modified mice did not experience the synapses pruning processes that are necessary for survival. Without pruning during sleep, memories become faded and unclear.

The researchers concluded that sleepiness pushes neurons to produce Homer1A and begin to clear out the tired brain of overflowing information and get it ready for another day of experiences and learning. However, other researchers question whether this is the definitive reason for sleep.

Sleep is mysterious and it is hard to study, because of the many variables that could cause it to be altered. Most of the time studies about sleep and the brain are inconclusive because it is difficult to tell if the changes in the brain that occur during night time are caused by sleep or the biological clock. Researchers are continuing to study sleep and find an answer to the question, what is the purpose of sleep?