Dreams are mental experiences that are formed in the brain during sleep. Many parts of the brain contribute to dream creation. The result of this weave of biochemistry and imagination is an intensely activated brain that serves up dream experiences that are strongly emotional and ruled by lapses in logic and bizarre mental imagery.
REM Sleep and Muscle Paralysis
Most dreams take place in rapid eye movement (REM) sleep. Dream scientist Allan Hobson has shown that, during REM, the brain is flooded with the neurotransmitter acetylcholine and serotonin levels drop drastically. As a result, the motor neurons for the entire body are blocked. This is a protective measure so we do not physically act out while dreaming, such as when battling lions and tigers in a nightmare. When this system is disrupted, dreamers develop REM Behavior Disorder, a dangerous condition that can result in injury of themselves and their sleep partners.
In November 2009, a homicide case in Wales was declared accidental because of the man's successful argument that the killing took place when a man was dreaming of fighting off an intruder. He killed his wife of 40 years in the process.
Super-Charged Activity
REM dreams are also fueled by unusually high brain activity in the brain stem, the oldest part of the brain, evolutionarily speaking. These brain pulses, known as PGO pulses, turn on the flood of acetylcholine, but also might be responsible for the sudden shifts in dream scenery as different parts of the brain are triggered. One minute we are flying through the sky and the next we are yelling at our parents in our childhood home. Hobson argues that this bizarre effect is our higher brain trying to write narratives out of these random brain signals.
Constructing Dream Stories
However, psychiatrist Mark Solms has shown that brain-damaged patients can still dream even when the brain stem is damaged. So dreaming and REM sleep are not the same, but they are highly correlated. Arguably, another important brain function necessary for dreaming is weaving a plot around the visual imagery, wherever it is generated. This "story-building" activity occurs when the neurotransmitter dopamine is flushing through the frontal lobes. So perhaps it is not merely high activation of a specific neurotransmitter that causes dreams, but the confluence of several threads of strong neurochemical action. This complex weave is stitched together in stories and experiences that make the most of the fireworks in the brain every night.
Logic Out the Window
One aspect of the brain function of dreams that all scientists agree on is that the prefrontal cortex is practically asleep during dreams. This area of the brain is specific to humans, and is the center of logic, abstract thought and language. With logic thrown out the window, we do not question the bizarre experiences in dreams. We go along for the ride, like it is no surprise that we are eating lunch in the old high school cafeteria again and we're naked.
Does this acceptance of the impossible have a function? Some dream researchers, such as Harvard psychiatrist David Kahn, suggest that the ability to forget who we are and what is normal in dreams might free the brain for creative thinking. Given that many scientists, artists and inventors from around the world claim they found the answer to their problems in their dreams, maybe the power of the dreaming brain is precisely this ability to let go of logical control and take cues from other creative processes.
References
- BBC News: "Camper van 'Dream Killer' Brian Thomas Freed by Judge"
- "Dreaming: An Introduction to the Science of Sleep"; J. Allan Hobson; 2002
- "The Mind at Night: The New Science of How and Why We Dream"; Andrea Rock; 2004
