The Science of Sleep: Unraveling the Mysteries of Our Dream World

Mike Birbiglia, a comedian, had a unique and dangerous experience while sleeping. One night in a hotel, he dreamed that a missile was heading straight for his bed. In a panic, he jumped out of the window in his dream—and in real life. This resulted in a two-story fall, a closed window, and 33 stitches. After that, Mike began sleeping in zipped-up sleeping bags for his own safety.

This story highlights that sleep isn’t just a time when our brains or bodies shut down. In fact, sleep is a different state of consciousness. Only recently have scientists started to explore the complexities of sleep—why we do it, what happens in our brains during sleep, and the effects of sleep deprivation.

When we sleep, our brains are still active, and our sensory perceptions remain slightly open. Just like Mike Birbiglia’s sleepwalking incident, our sleep experiences can be wild. This exploration of sleep will guide you through this altered state of consciousness, shedding light on the mysteries of the human mind, including your own.

Technically, sleep is a natural, reversible, and nearly complete loss of consciousness. While we spend about a third of our lives sleeping, and we know it’s vital for health and survival, scientists still debate why we sleep. Some believe it’s for physical recuperation, allowing cells and neurons to repair themselves. Others suggest sleep supports growth, as growth hormones are released during sleep. Sleep is also linked to mental function, helping with memory, processing daily events, and boosting creativity.

The study of sleep has come a long way, especially since the early 1950s. Eugene Aserinsky, a graduate student in Chicago, used an electroencephalograph (EEG) on his son, Armond, while he slept. This machine measured brain activity and revealed that the brain doesn’t just shut down during sleep. Aserinsky discovered what we now call REM (Rapid Eye Movement) sleep, a stage where the brain is highly active even though the body is in deep rest. This was a significant finding in sleep research.

Since then, scientists have identified four distinct stages of sleep, each with its own brainwave patterns. When you first go to bed, your brain is still active, showing alpha waves. As you start to sleep, your brain shifts to non-Rapid Eye Movement (NREM) stage one, characterized by irregular waves. This is when you might experience hypnagogic sensations—those brief moments where you feel like you’re falling, and your body jerks.

As you relax further, you enter NREM-2, where rapid brain wave bursts called sleep spindles occur. You’re now definitely asleep but could still be easily awakened. NREM-3 brings slow delta waves and deeper sleep. Although brief dreams can occur in these first three stages, the most vivid dreams happen in REM sleep, where the brain is most active, but the body is paralyzed, except for the eyes. This sleep cycle repeats every 90 minutes throughout the night.

Sleep is crucial for our health, and lack of sleep can have serious consequences, including mental and physical health issues. Chronic sleep deprivation is linked to depression, weight gain, immune system suppression, and slower reaction times, which is why it’s dangerous to drive when tired.

There are also various sleep disorders, such as insomnia (difficulty falling or staying asleep) and narcolepsy (sudden sleep attacks). Narcolepsy might be caused by a deficiency in the neurotransmitter hypocretin or, in rare cases, brain trauma or disease. Another common disorder is sleep apnea, where a person temporarily stops breathing during sleep, causing them to wake up. Mike Birbiglia’s condition was a REM sleep behavior disorder, where the body doesn’t become paralyzed during REM sleep, leading to dangerous behaviors like sleepwalking.

Then there are night terrors, often experienced by children, which involve intense fear, screaming, and thrashing, usually without memory of the episode. Night terrors happen during NREM-3 and are different from nightmares, which occur during REM sleep.

Dreams, a major part of sleep, are vivid, emotional images that can be bizarre and surreal. People spend about six years of their lives dreaming, often reflecting daily experiences. Dreams can range from mundane activities to wild and bizarre scenarios. But why do we dream? There are several theories.

Freud suggested that dreams offer wish fulfillment, representing our unconscious desires in a symbolic form. However, this theory lacks scientific support. Other theories include the information processing theory, which suggests that dreams help us process and store memories from the day. The physiological function theory proposes that dreams promote neural development and maintain brain pathways. Cognitive development theory sees dreams as a reflection of our knowledge and understanding of the world, engaging the same brain networks used during daydreaming. Finally, some theories suggest that dreams are simply a byproduct of neural activity during REM sleep.

Although the purpose of dreams is still debated, REM sleep is essential for both physical and psychological health. Next week, we’ll explore other altered states of consciousness, including the effects of drugs on the brain and the potential for hypnosis to influence behavior. But for now, you’ve learned about the four stages of sleep, the major theories of dreaming, and the importance of sleep for overall health.