Only a Dream
By Rosalind Kaplan, MD
There seemed to be a lot of interest in my post on sleep from two weeks ago. I'm not surprised; sleep problems are extremely common. As my previous post indicated, short sleep duration is a widespread problem, but other sleep disorders are also more common than you might think. Sleep apnea, which interrupts normal sleep with periods of low oxygen, and can lead to hypertension, daytime sleepiness, and other health issues, affects up to 20% of the US population, and a large pre-pandemic study showed that a full one-third of Americans had problems with insomnia. The prevalence of insomnia increased to around 40% during the pandemic, especially among healthcare workers and people with covid-19; we won't know for quite some time whether it will decrease again post-pandemic
Obviously, if we're not sleeping, we are also not dreaming. Do dreams matter to our health or to other aspects of our lives? If you're like me and sometimes have disturbing or frightening dreams when you do sleep, it might seem like not dreaming would be preferable. At least once a week, my husband has to wake me from some disturbing dream during which I am yelling or screaming. That doesn't sound very healthy, does it? And what about those recurrent anxiety dreams many of us have (arriving for a test for which we forgot to study, or being naked in public) or the seemingly universal dream of falling, but waking up before we hit the ground? It seems that we need our dreams and they serve a purpose, even if they are not pleasant. As mysterious as dreams are, there must be some explanation, right?
There have been many theories over the years as to why we dream. Some cultures, past and present, believed in mystical meanings of dreams, or that dreams predicted the future. Freud taught that dreams were manifestations of hidden, unconscious desires, often with sexual content, and often disguised, but interpretable in the Freudian framework. A little later, Jung brought in his own theories that dreams reveal, rather than conceal and that they are an expression of our imagination. He believed that dreams helped to integrate our conscious and unconscious minds, and didn't need to be interpreted to do so.
Neuroscientists and neuropsychologists have studied dreams in the last few decades. The 'garbage disposal' theory of dreams from the 1980's proposed that the images and thoughts in dreams were the brains way of getting rid of useless and unnecessary information, a sort of 'purge' of the brain's garbage through the electrical activity of a dream. If this were true, dreams would be important in the sense that they 'clean out' the brain, but the content would be useless, so remembering or examining dreams would be a waste of time. This explanation is kind of dissatisfying because it can't explain recurrent dreams, or universal dreams, or the emotions that many of us find lingering when we awake from a particularly vivid dream. Nor would it make sense for us to remember some of our dreams, which most people do.
More recent studies of dreams show that, while 'clearing out' of excess information may be part of the role of dreams, it's not at all as simple as that. MRI's and PET scans, as well as tests of memory and creativity show that dreams impact brain function in multiple ways.
As you might have noted during your own dreams, visual images - which are often unusually vivid and even maybe psychedelic- dominate dreams. This is because during REM sleep, when dreams occur, the visual areas of the brain are highly active, while the areas for verbal processing are relatively shut down compared to our waking state. Essentially, visual dreams are hallucinations during sleep. Some neuroscientists have come to believe that we need dreams, which are visual input when we are asleep and thus have no actual visual input, in order to 'defend' the visual cortex of the brain--that is keep it active and prevent other senses from taking it over when it is not getting visual input. This theory is backed up by the fact that people born blind, and thus not using their visual cortex, do not have visual dreams.
Other neuroscientists have shown that memory is improved or consolidated during sleep, and that creativity, as demonstrated by coming up with new solutions to such problems as the solution to a maze or other spatial puzzle, is increased by REM sleep. Perhaps during sleep, then, we are processing visual information that our brains deemed superfluous in our waking state, and integrating that new information into what we already knew.
A final theory is that dreams are like fire drills--a way that we practice survival techniques for potential serious dangers. If this is the case, it might make sense that we are trying to figure out how to pass that test that we didn't study for (hey, you! remember to study next time!!) or escape a wild animal in the woods (something that we may not really have to do but our ancestors would have) or save our dignity when caught unclothed in public.
Maybe my terrifying dreams, the ones I wake from screaming, or my angry dreams, from which I wake yelling, are actually helping me cope in the real world, then. My brain might be finding solutions to problems, using information I might otherwise not have access to. It might be improving my memory or my creativity. And there's a good chance it is protecting its own visual cortex, to keep my eyes and brain working together properly. At very least, it's cleaning itself out so I have room to shove more junk into it during the day...
In any of these cases, I wouldn't want to give up dreaming (yeah, I mean actual dreams, not the 'wish' type of dreams), and that means I need to sleep. Preferably without any external chemical assistance to help me sleep, since hypnotic and sedative medications often have significant effects on the amount of REM sleep a person gets.
For more information on sleep disorders: