Essentials: Use Sleep to Enhance Learning, Memory & Emotional State | Dr. Gina Poe

Introduction to Sleep Stages00:00

Sleep is fundamentally different from wakefulness and cannot be replaced by any state of wakefulness. Brain chemistry during sleep is completely different from waking states. The two major states of sleep are non-REM and REM, and these states are entirely different from each other. Within non-REM sleep, there are three distinct stages: stage one, stage two, and stage three.

Stage one occurs when first falling asleep and is characterized by dozing with a fast gamma rhythm in the brain. Stage two is a transient state between wakefulness and deep sleep that contains sleep spindles and K complexes. Stage three, or slow-wave sleep, involves big slow waves that sweep through the brain and is responsible for cleaning the brain and restoring the body from wakefulness.

REM sleep, or rapid eye movement sleep, is characterized by the most active dreaming. When people are woken from REM sleep, they almost always report bizarre dreams. A perfect night's sleep consists of cycling through these four states every 90 minutes, with approximately five cycles per night, totaling 7.5 to 8 hours of sleep.

Early Night Sleep and Memory Processing02:30

The first four hours of sleep are particularly important for memory processing. When new information is learned or new sensory-motor experiences occur during the day, early sleep dreams incorporate those experiences much more than later sleep dreams. As memories consolidate from the hippocampus to the cortex in a distributed fashion, the dreams incorporating those memories also move later into the night.