Most of us dream four to five times a night during periods of rapid eye movement, or REM, sleep, which interrupt deep sleep at approximately 90-minute intervals. Since REM sleep and it's link to dreaming were discovered in 1953, much has been learned about the changes in the brain state that triggers . We now know that the brain alternates between two peak states of activity: one during waking, when the brain is controlled by the neurotransmitters norepinephrine and serotonin, and one during REM sleep, when it's controlled by the neutransmit ....