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How Fever Dreams Work

Dream Weaver
They look like angels when they're in the REM phase of their sleep cycles.
They look like angels when they're in the REM phase of their sleep cycles.
Peter Augustin/Taxi/Getty Images

What's in a dream? Or, more specifically, what in the name of Morpheus is a dream? Why have them? Are they, as the ancients thought, a mode of communication with the gods? Or was Sigmund Freud right when he posited that they represent repressed desires? Maybe Carl Jung was on to something when he suggested that dreams tapped into a collective unconscious.

Neurologists, of course, aren't into dream interpretation. They think all that stuff is poppycock. In fact, for a long time, many scientists were convinced that dreams were just an accidental byproduct of our synapses randomly firing while we sleep. They had a name for it — "activation-synthesis hypothesis" [source: van der Linden]. The idea was that during the rapid eye movement (REM) stage of sleep, a bunch of disconnected images bump and thump through our brains. When we wake up, we automatically string the images together into a semi-coherent sequence. We come up with a dream story because that's just how our minds work.

But more recently, a series of innovative studies using electro-encephalography (EEG) and magnetic resonance imaging (MRI) point to a different way of thinking about dreams. Italian researchers used EEG technology to study the dreaming process for a cohort of subjects. They put some people in a sound-proof room, hooked them up to EEG machines, and, after they'd drifted off, woke them up at different points and had them write down what they'd dreamed [source: van der Linden].

We go through five stages of sleep and different combinations of brain waves show up at each stage. There are four different kinds of brain waves: alpha, beta, delta and theta. Each one moves at a different speed. We dream the most during REM sleep stage, which features a mix of brain waves very similar to our waking state. The study participants who remembered their dreams best were the ones who had the highest quantity of theta waves in their frontal lobes. Theta waves are low-frequency. The researchers were intrigued because there's another instance when theta waves are present in the frontal lobes, and that's when we're building and recalling memories. So there appears to be a close link between dreaming and remembering.

A separate study conducted with MRI equipment found a relationship between dreams that are particularly graphic, weird and highly emotional, and the parts of our brains known as the amygdala and the hippocampus. The amygdala is linked to how we deal with emotions while the hippocampus is involved in processing memory.

A third study discovered that our dreams are channeled through, and possibly even originate in, the lingual gyrus, an area of the brain related to emotion, memory and visual activity. Putting all this together, it seems that dreams use the memory system to help us deal with raw emotions. Turning intense emotions into memories helps neutralize them, reducing stress and anxiety. If this is true, it would help explain why people deprived of REM sleep for too long can often develop mental health issues [source: van der Linden].