Sleep can sometimes be elusive. We yearn for it, but it often cannot be found. But sleep is critical for a healthy brain. We need sleep. Humans are circadian beings and evolved to require a certain rhythm, which includes healthy sleep patterns. Without sleep, we cannot learn, remember, feel, or function. It must be important because when we sleep we lose the ability to defend or feed ourselves.
What is sleep? Sleep involves the cycling of REM and NREM stages. A full cycle is about 90 minutes. This cycle is then repeated three to six times in a night. Anatomically, sleep is complicated and is really about lack of wakefulness. Wakefulness mechanisms, in a simplistic description, require the coordinated activity of connections of the thalamus, the hypothalamus, the cortex, and the brainstem—all different parts of the brain.