A few of these scenarios may ring a bell: flying, falling, climbing to great or frightening heights, trying to run from a threat through a sludge of quicksand, sharing an embrace with a mysterious stranger or a co-worker, or popping up suddenly in your grade two classroom and then getting turned upside-down by a twister. How do we get to these places? How do dreams happen?
First, we have to fall asleep, of course. Scientists believe adenosine, a natural compound, accumulates in our blood during our waking hours, compelling us toward sleepy state. Gradually, the heart rate and breathing slow, and muscles all across the body relax more and more.
At about the 90-minute mark, after most people have fallen through deeper, slow wave sleep, they switch into a cycle of sleep characterized by rapid eye movement (REM). REM sleep is where the most vivid and frequent dreams happen.
The body lies mostly still through the REM cycle, but the brain is nearly as active as when it's fully awake. Motor signals from the brain to the body are inhibited by certain neurotransmitters which, for all intents and purposes, temporarily paralyze us. It's lucky for us that these neurotransmitters kick in. Without them, we'd all be running from monsters in our pajamas or trying to fly out of our beds. Your eyes, however, remain responsive to these signals. They still dart back and forth, implying activity – dreams – occurs during sleep.
Those dream images are thought to originate in the visual centre of the cerebral cortex, the brain's grey matter and the mind's hub for memory, awareness, consciousness, and thought. While the part of your visual cortex that takes in new images sleeps right along with you, the part that interprets images stays wide awake. So, basically, your brain gets down to business, trying to makes sense of all the bits of memory and imagination.
So, temporary paralysis, rapid eye movement, certain parts of the brain shutting down while others light up – why does our body work so hard to let us dream? Read on...
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