Why Do We Sleep?
Experiments suggested that the brain itself actively generates sleep. When certain parts of the brain were stimulated by an electric current, sleep occurred. The discovery of rapid eye movement sleep in 1951 gave further evidence of a sleep-active brain. Then scientists identified specific populations of neurons in the pons and medulla of the brain stem that directly affect REM sleep.
Though it is now agreed upon that sleeping is an active phenomenon influenced by specific neurons, the bewildering complexity of the brain continues to prompt debate on the precise location of the neurons and how they interact. Neurons communicate with one another through chemicals called neurotransmitters. Millions of such interactions are necessary for you to read this sentence.
“Sleep may not be the result of one or even of several discrete sleep centers,” says Dr. Wallace B. Mendelssohn, a sleep specialist at the State University of New York at Stony Brook. “Possibly it results from the complex interaction of sleep-generating neurons with neurons that control such aspects of physiology as respiration and blood pressure.”
The ultimate question may not be what it turns neurons on, but why. Some theories: By lowering the body’s thermostat, sleep conserves energy. REM may also facilitate learning or brain development or reinforce individual behavior patterns.