Dreaming aka The Rinse Cycle

Sleep: it’s quite possibly the most dangerous thing that an animal could do. Your senses are shortened, your muscles are relaxed, and your consciousness is off in a reality that you have created for yourself (dreams). Despite the great advances that the scientific community makes every day, this task that takes up 1/3 of our lives is not well understood. What is the purpose for sleep? A physician once told me the only reason we know sleep is important is because we do it, but why? What is happening that is so vital to our existence that we take the risk to dream? One group of scientists thinks they have found the reason.

Maiken Nedergaard and her team at the University of Rochester used live mice to study the physiology of brains while the mice slept. The fascinating discovery was that the interstitial space in the brains of the mice increased by 60%. This means that their brains literally shrank in size while they slept. The purpose of this shrinking is to help the flow of the cerebrospinal fluid (CSF). During the day, CSF is at a slow trickle through the brain, but at night it is as dramatic as someone turning on a faucet full blast. According to the National Multiple Sclerosis Society, CSF is the clear, nutrient-filled fluid that bathes the brain and spinal cord with the needed materials to operate. The researchers at Rochester found that like the circulatory system carries oxygen and nutrients to the body and helps remove waste products like CO_2, the CSF is working in much the same way.

Importantly a chemical known as β-amyloid is one of the primary wastes being removed. In an interview about her research, Dr. Nedergaard compared what the CSF is doing to that of a dishwasher. It removes the dirt and grime from the brain and leaves it ready for use the next day. Elevated β-amyloid has been linked with Alzheimer’s disease. Research has shown that in a normal person’s β-amyloid levels increase throughout the day. If the β-amyloid is not removed it can result in amyloidosis (a buildup of miss-folded proteins deposited into the tissue) which is thought to be a primary cause Alzheimer’s. The nonfunctional proteins work as toxins against brain tissue and begin to degrade it. This draws an interesting link between Alzheimer ’s disease and its common symptom of reduced quality and quantity of sleep. This may also lead to a simple way to slow the progression of Alzheimer’s which is simply to regulate sleep.

Sources: 

http://www.sciencemag.org/content/342/6156/373

http://www.nationalmssociety.org/Symptoms-Diagnosis/Diagnosing-Tools/Cerebrospinal-Fluid-(CSF)#