4 theories to help explain why you dream: ‘The dreaming brain is as active as the waking brain,' neuroscientist says

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When you're in deep sleep, your mind can paint vivid scenes like being chased by fictional serial killer Michael Myers or unexpectedly bumping into your ex — but why?

"I can say with certainty that dreams arise from our brains and specifically our brains' electrical activity," Dr. Rahul Jandial, a neurosurgeon and neuroscientist, wrote in his recently published book, "This Is Why You Dream."

Jandial has searched for the answer to why we dream for years.

"We now know all consciousness is powered by electricity, including dreaming, and it turns out the dreaming brain is as active as the waking brain – sometimes even more so," he said.

Just 8% of Americans say they never recall dreaming after waking up, according to a 2004 Gallup survey of 1,003 adults — leaving 92% of people who either dream every night, a few times a week to a month or very rarely.

Here are four theories based on research from fellow experts that Jandial posits in his book as potential reasons why you dream.

4 theories to help explain why you dream

1. 'Threat rehearsal'

One theory about why you dream is that it is "a kind of threat rehearsal, a way to practice recognizing and responding to threats in a safe way," Jandial wrote.

Think about a dream where you're being chased by someone; the dream can somewhat give you a practice run for how you can navigate the situation in real life.

"In this theory, dreams are like a virtual simulation where we can test different responses and imagine the consequences," he said.

Jandial cited a study where professor of neurology, Dr. Isabelle Arnulf, asked her students about the content of their dreams the night before a major exam. Findings showed that "students who dreamed about the exam frequently did about 20 percent better than those who never dreamed about it," whether the dream was positive or not.

2. Therapy

A different theory considers that "dreams have therapeutic value, serving as a kind of nocturnal therapist, helping us digest and metabolize anxiety-provoking emotions."

Sometimes dreams allow you to confront issues that are bothering you in your waking life.

Consider the example Jandial provided of a study conducted by Rosalind Cartwright that discovered "dreams could by themselves be accurate predictors of who would—and who would not—recover from post-divorce depression."

According to Cartwright's study, the divorcees who had the best recovery reported having dramatic dreams that were a combination of old and new experiences in their lives.

"Cartwright concluded the recently divorced test subjects were working out their negative feelings about their former spouse in their dreams," he wrote. "This, she said, had the effect of diffusing the emotion and preparing the dreamer to wake up ready to see things more positively and to make a fresh start."

3. Brain functionality

A straightforward theory about why we dream is that dreaming can be good for "keeping the brain tuned and ready even during sleep."

In other words, the processes that the brain experiences as you're dreaming may be helpful for brain functionality and keeping your brain sharp.

A theory related to this overarching idea of brain functionality "proposes that dreaming has evolutionary benefits because the accompanying bursts of mental activity keep neural networks finely tuned, as a sort of pilot flame for the brain," Jandial said.

"That way, if we are awakened, the brain can quickly become alert and engaged."

4. Creativity

An interesting hypothesis about why you dream is that dreams can "lead to more flexible and creative thinking" that can shift the tunnel-vision version of your mind in your waking life, Jandial said.

When dreaming, "adrenaline is turned down" which allows you to turn off your fight-or-flight responses that may otherwise push you away from considering new possibilities that cause fear.

But adrenaline is still present while you're sleeping; think about how your heart can race when you're dreaming about being chased. Adrenaline's simply lowered when you're dreaming.

Certain narratives in dreams can help you "navigate the world with all its complexity and give us the best chance of dealing with the widest set of challenges we may face."

Even with all of the theories and extensive research, "no theory has emerged as to the single reason humans have retained the need to dream," he said.

"In fact, the evidence suggests all these theories are valid to some degree, intertwined and interdependent."

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