Every one of us slips into this mysterious state of consciousness every night, yet we are only now waking up to its mind-altering powers
“The interpretation of dreams is the royal road to a knowledge of the unconscious activities of the mind.” So wrote Sigmund Freud in his 1900 classic The Interpretation of Dreams. He saw this idea as a “once in a lifetime” insight, and for much of the 20th century the world agreed. Across the globe, and upon countless psychoanalysts’ couches, people recounted their dreams in the belief that they contained coded messages about repressed desires. Dreams were no longer supernatural communications or divine interventions - they were windows into the hidden self.
Today we interpret dreams quite differently, and use far more advanced techniques than simply writing down people’s recollections. In sleep laboratories, dream researchers hook up volunteers to EEGs and fMRI scanners and awaken them mid-dream to record what they were dreaming. Still tainted by association with psychoanalysis, it is not a field for the faint-hearted. “To say you’re going to study dreams is almost academic suicide,” says Matt Walker at the University of California, Berkeley. Nevertheless, what researchers are finding will make you see your dreams in a whole new light.
Modern neuroscience has pushed Freud’s ideas to the sidelines and has taught us something far more profound about dreaming. We now know that this peculiar form of consciousness is crucial to making us who we are. Dreams help us to consolidate our memories, make sense of our myriad experiences and keep our emotions in check.
Changing patterns of electrical activity tell us that the sleeping brain follows 90-minute cycles, each consisting of five stages - two of light sleep at the start, then two of deep sleep, followed by a stage of REM, or rapid eye movement sleep (see diagram). There is no characteristic pattern of brain activity corresponding to dreaming, but as far as we know all healthy people do it. And while dreaming is commonly associated with REM sleep, during which it occurs almost all of the time, researchers have known since the late 1960s that it can also occur in non-REM sleep - though these dreams are different. Non-REM dreams tend to be sparse and more thought-like, often without the complexity, length and vivid hallucinatory quality of REM dreams.
Despite their differences, both types of dreams seem to hold a mirror to our waking lives. Dreams often reflect recent learning experiences and this is particularly true at the start of a night’s sleep, when non-REM dreaming is very common. Someone who has just been playing a skiing arcade game may dream of skiing, for example (Sleep, vol 33, p 59). The link between waking experience and non-REM sleep has also been observed in brain scanning studies. Pierre Maquet at the University of Liège, Belgium, looked at the later stages of non-REM sleep and found that the brains of volunteers replayed the same patterns of neural activity that had earlier been elicited by waking experiences (Neuron, vol 444, p 535). Many REM-sleep dreams also reflect elements of experiences from the preceding day, but the connection is often more tenuous - so someone who has been playing a skiing game might dream of rushing through a forest or falling down a hill.