Dreams 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 dreams. 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 neutransmitter acetylcholine. When we're awake, we're rational, self-aware and able to focus, pay attention, respon