Understanding Your Brain on Sleep
Superlatives about the human body tend to center around the brain. Fastest, neediest, most powerful — it is, after all, what makes people human. That 3-pound hunk of tissue demands 20 percent of the oxygen and calories the body takes in, communicates with 45 miles of nerves in the skin, contains individual neurons that can live more than a century, and generates enough energy when a person is awake — between 10 and 23 watts — to power a light bulb.
But the fun really begins when humans go to sleep. Scientists long have wondered why the body requires that people spend one-third of their lives unconscious. Although an individual may look quiet when she’s with the sand man, studies have shown that the brain is more active in sleep than awake.
Sleep, and the process of dreaming, helps the brain consolidate memories in ways that researchers are only beginning to understand.
Studies released in 2013 indicate that the brain is up to something else when humans sleep: It’s taking out the trash. The lymphatic system that moves cellular waste out of the body doesn’t reach into the brain.
Instead, the brain is bathed in cerebrospinal fluid. When you sleep, your glial cells actually shrink up to 60 percent to widen the channels and sweep toxins away more efficiently. (Derived from the Greek word for “glue,” glial cells are the connective, supporting cells in the nervous system.) Now scientists are studying this newly discovered glymphatic system to see whether it can be brought to bear in the battle against Alzheimer’s and other forms of dementia.