"Acetylcholine is a neurotransmitter, a chemical that carries messages between brain cells. Most dreams occur during rapid eye movement, or REM, sleep, when acetylcholine levels are high, as they also are during alert wakefulness. By observing the effects of deficiencies, scientists know that acetylcholine is essential to sleep, dreaming, learning and memory, although the precise nature of the connection is unclear. A healthy diet gives you all you need, but increasing your intake of foods rich in lecithin and B vitamins might help encourage more vivid dreams.
Stages of Sleep
A healthy sleep cycle progresses in five stages, each with distinctive brain wave patterns. The duration of each phase varies with age but on average, one entire cycle lasts about 90 minutes. Stage one is the groggy phase just before you fall asleep. During stage two, an EEG will show sudden spikes in electrical activity as your brain tries to disengage from the waking state and descend deeper into sleep. Stages three and four are restful, when brain waves are slow, strong and synchronized. Most dreaming takes place during the REM, stage, when blood flow to the brain increases, electrical activity parallels a state of high alertness, and the eyes move as though scanning a scene."
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