EWhen exposed, the undulating surface of the brain is glistening and opalescent, punctuated by arteries and veins. Give a part of it the slightest electric shock with a pen-like probe and it will activate the neurons in that spot. Neurosurgeons use this technique during some types of brain surgery to locate the source of seizures or to prevent damage to vital tissue.
While the procedure is taking place, the patient is awake but feels nothing, because the brain does not have so-called nociceptors or pain sensors. Because the thin, outer layer is responsible for consciousness, language, perception, memory and thinking, moving the probe from place to place can reveal a lot. It can bring back smells, memories of childhood and even nightmares. Use the probe to touch a specific part of the brain: nightmare on. Remove the probe: nightmare out. In this way, I saw firsthand how dreams are truly part of the neural architecture. They are very much built into our bodies.
I have also observed the power of dreams to persevere despite a terrible injury. I have seen children who have had half their brains removed as a last resort for intractable seizures still report dreaming. I’ve come to realize that almost everyone has dreams, even if we often don’t remember them. And of course people who are born blind dream. They compensate for their lack of visual content by experiencing more sound, touch, taste and smell than sighted people.
Recent research suggests that dreams may also play a bigger role in our sleep than previously thought. For decades, scientists studying dreams focused on just one stage of sleep, called rapid eye movement, or REM, sleep. They concluded that we spend about two hours a night dreaming, more or less. If you do the math, this equates to about a twelfth of our lives being immersed in dreams, one month out of the year. That would represent a huge commitment to dreams. But it turns out that even that can be a gross underestimate. When researchers in sleep labs wake study participants at different times—not just during REM sleep—they discover that dreaming is possible at any stage. It is conceivable that we actually spend almost a third of our lives dreaming.
Dreams are the product of profound changes that the brain automatically undergoes every night. The rational, executive network in the brain is turned off and the imaginative, visual and emotional parts are turned all the way up. As a result, the dreaming mind is given free rein in a way that has no parallel in our waking lives. We couldn’t think this way while awake even if we tried.
Far from being inactive, the sleeping brain burns glucose and pulses with electricity to produce dreams. But why spend this kind of energy creating imaginative and highly emotional nighttime experiences for an audience of one – especially when they often seem nonsensical? I am convinced that unless dreaming were an essential feature of our minds, we would not expend the resources necessary to dream, while making ourselves more vulnerable to predators.
There are a number of theories that attempt to explain the evolutionary benefits of dreaming. These include keeping our minds alert while we sleep, making us more intuitive, providing outrageous scenarios so we can better understand the everyday, serving as a nighttime therapist, and rehearsing threats so we are better prepared. Evidence for the latter includes a study It found that prospective medical students who dreamed that their entrance exam would go terribly wrong tended to do better when they took it the next day.
I believe there is some truth in all these theories. Because our brains have developed over millions of years, it seems reasonable that the role of dreaming has expanded and evolved along with them. We are not trying to find any evolutionary advantage for waking thought. Why should we try to limit the purpose of dreams?
During my training I worked in transplant surgery for some time. When we put hearts and lungs, kidneys and livers in, we never connected the nerves. Think about that for a moment, as I do. What I realized was that our most vital organs are passive participants in the sleeping body. This suggests to me that it is not so much the body that needs to sleep, but the brain. In effect, the dreaming brain shuts down the body through a form of chemical paralysis, freeing itself to fully experience the dream without risking physical harm if it plays out.
What should we conclude from all this? In essence, dreaming is not an optional extra, a kind of decoration on top of the serious business of sleep. No, us need to dream. When we are sleep deprived, the first thing we catch up on is dreaming. Spend an entire night awake, as I often did while training, and the next night explodes into vivid REM dreams, instead of following the normal 90-minute sleep cycle. And if you have had enough sleep but are dream deprived (something that is only possible through interventions in a sleep laboratory), you immediately start dreaming as soon as you fall back asleep.
Even in the complete absence of sleep, vivid dreams can occur. Among people with fatal familial insomnia, a rare and fatal genetic disease that makes sleep impossible, the need is so strong that dreams escape their normal boundaries and spill into waking life.
So much attention is being paid these days to the benefits of sleep for our mental and physical health. That is completely justified. But given the many potential benefits of dreaming to our waking lives, it may not be the sleep we really need, but the dreams.
Rahul Jandial is a neuroscientist and author of This is why you dream (Cornerstone).
Read further
Why we sleep: The New Science of Sleep and Dreams by Matthew Walker (Penguin, £10.99)
When brain dreams: Exploring the science and mystery of sleep by Antonio Zadra and Robert Stickgold (WW Norton, £13.99)
The formless discomfort: My Year in Search of Sleep by Samantha Harvey (vintage, £9.99)