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You Asked: How do dreams work?

When you dream part of your brain is 'awake'
how dreams work

When we dream, is it really like having a mini movie studio in our head—churning out content from both our conscious and subconscious? Disney created an excellent analogy for how dreams work in Inside Out, but the complex systems responsible for dreaming aren’t exactly the same as having your own personal Hollywood production crew.

The National Sleep Foundation states that dreams are a “purely ‘mental’ activity that occur in the mind while the body is at rest. However, some people act out their dreams—a characteristic of a rapid eye movement (REM) sleep behavior disorder. Sleep is an incredibly complex phenomenon, and there are still many unanswered questions about the process. Because studying dreams means waking someone up, there are methodological hurdles to fully understanding all the mechanisms responsible for dreaming.

A Texas A&M Health Science Center College of Medicine neuropsychologist said dreams occur when the cortical parts of our brain (the areas responsible for higher-order functions like language) are active during sleep, while the lower portions prevent messages from getting to our body that would otherwise cause movement or activity.

An imitation of life

How do scientists explain dreaming? It’s complicated. The condensed explanation is there are a complex series of chemical steps and circuits that serve as a “switch” to allow the higher, cortical parts of the brain to be active while the body does not respond to signals as it normally does during the day. Thus the parts of the brain that are ‘on’ during dreaming are the same ones we activate to see, remember, smell, taste and move.

“We don’t actually ‘see’ or ‘hear’ anything during the day; it’s our brain processing sensory inputs and synthesizing this to form our experiences,” said Jared Benge, PhD, ABPP-CN, assistant professor with the Texas A&M College of Medicine and a neuropsychologist with Baylor Scott & White Health in Temple. “With a dream, we don’t have the sensory inputs, but the parts of our brain that perform these processes are still active—so our experiences seem ‘real.’”

Other factors—such as the cyclical nature of sleep itself (including areas of the brain that act as a clock to establish our sleep/wake cycles), pathways of certain neurotransmitter release that signal sleep onset and maintenance, and the fact that sleep has several different stages as the night wears on—all impact how and when we dream. All of these mechanisms enable sleep, and dreaming is the product of sleep.

It all begins with REM

“Dreaming happens most often during REM sleep,” Benge said. “If we looked at REM sleep on an electroencephalogram (EEG), a test used to detect electrical activity in the brain, our brains usually show activity very similar to wakefulness.”

Most people awakened out of REM sleep report experiencing their most vivid or strange dreams, although, there are some studies that indicate individuals in the slow wave sleep cycle may dream with these being fragments of more cohesive memories.

I dreamed a dream of time gone by

How quickly we recall the details of certain dreams also depends upon how deeply we’ve been sleeping, the content of the dream, and activities and routines we engage in when we wake up. So, everyone dreams, but not everyone remembers their dreams.

Many of the most vivid and odd dreams we experience occur during REM phase sleep, and individuals woken from this stage of sleep frequently report the bizarre phenomena we usually associate with memorable dreams,” Benge said. “But, more mundane and less bizarre dreams are sometimes reported during slow wave sleep as well.”

One man’s dream is another man’s nightmare

Benge said that what people consider dreams versus nightmares will rely upon the individual’s specific interpretation. “It’s subjective to what negative or disturbing content mean to that person,” he said. “For an Olympic athlete, running 26 miles in your dreams is a peak example of achievement and a great experience. For me, there better be something horrific chasing me in my dreams to do a 26 mile run. Their dream is my nightmare.”

Kids are especially prone to to a phenomena known as “sleep terrors” marked by panic-type symptoms (blood pressure increases, sweating, agitation, screaming). These will often awaken children and they will normally recall a terrifying incident.

“Because you can only really know what someone is dreaming by asking them, it’s a pretty subjective enterprise to classify dream content,” Benge said.

Dream production and the subconscious

According to Benge, there are many fascinating correlative studies about dream content, but correlation does not always mean there is a causation. For example: The events of daily life tend to be dreamed about more, and individuals in the middle of stressful situations are more likely to dream about what they’re going through.

“It seems possible that environmental influences—like inducing smells into the room where someone is sleeping—can sometimes induce what is dreamed about,” Benge said. “As a neuropsychologist, I’m most interested in the processes that underlay cognitive abilities like memory.  It seems that sleep and dreaming may serve an important role in the brain consolidating or moving recent events into long-term memory.”

Thus, dreams may reflect the organization—sometimes haphazard—of various fragments of memory and experience,” Benge continued. “But, to be clear, the ultimate answer is: It’s complicated, and, we’re not certain.”

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