Dr. Eagleman, why do we dream?
Over millennia, many ideas have been put forward to explain why we dream. Societies have long favoured mystical interpretations, such as messages from deities and higher entities, but nowadays we can look more rigorously for explanations. My research has led me recently to a new theory: dreaming is a screensaver. The idea is simple. If you go blind, the visual part of your brain (the visual cortex) is partially taken over by other senses. But it turns out the same thing happens if you just get blindfolded for about 90 minutes: we can see the other senses beginning their encroachment. What I realized is that the rotation of the planet puts us all in a blindfold experiment half the time. In other words, at night the visual system is disadvantaged compared to the other senses. You can still hear, touch, taste, and smell in the dark, but (for 99.99999% of evolutionary history) you can’t see. So how did brains deal with this? By blasting random activity into the visual system every 90 minutes during the night. Because brains are storytellers, the random activity takes on some semblance of plot and meaning, but fundamentally the purpose of a dream is to defend the visual territory against takeover. That’s why we dream. And, by the way, all animals dream.
Do you have an explanation as to why these dreams seem to go on for ages, as if you are dreaming an entire novel? But if someone suddenly wakes you up, the dream ends abruptly, as if it was meant to end at that moment. Have I only dreamt for a second? Or did I dream for a long time, but my brain created an abrupt ending?
Judging dream time is difficult. Sometimes, when you wake up from a dream, it seems like the events that happened must have spanned a long time – because those same events would have lasted a long time in waking life. For example, if you dream about taking a boat from America to Europe, you might judge the dream story to have taken weeks, while in fact the dreaming just took moments. This difficulty in judging dream time is compounded by the fact that we tend to write down our dreams or tell them to someone else – and in these cases we unwittingly add details to make the plot slightly more coherent. So something that was just an impression in the dream ends up taking a paragraph of explanation – and retrospectively we believe the dream must have lasted even longer.
Let’s move from dreaming to sleeping in general. Tell us about sleep.
We spend about a third of our lives in the strange, doppelganger-like state of sleep. Why? It’s still not clear. One view is that sleep is critical for restoring energy. Another view is that in the dark of the night it's safer to curl up in the corner of a cave and stay out of trouble. More modern theories propose that sleep is critical for processing events of the day and consolidating memories. Quite possibly all these ideas (and others) play roles; there’s no necessity to assume a single function of sleep.
Perhaps this is why Max Richter approached you a decade ago, when he was starting to compose SLEEP: he wanted to base it on as much scientific research as possible. What input did you provide, and how did you help him?
Max and I talked about rhythms in the brain – and how these rhythms change as you descend into different stages of sleep. These can be measured by using electroencephalography (EEG), placing electrodes on the outside of the skull. When you’re awake, we see a lot of fast and busy electrical activity in the brain, but as you fall into deeper and deeper stages of sleep, the activity slows into a large, coordinated rhythm. Scientists have long been interested in whether these rhythms can be entrained – in other words, could playing music at the rhythm of deep sleep help the brain maintain that state for a longer time? Max and I discussed these rhythms, and the central feature of his beautiful composition is its beautiful, slow cadence that matches deep sleep.
The hypnagogic state is the phase between being awake and falling asleep. During this time, it appears possible to influence your dreams. Many creative individuals, including Max Richter and David Lynch, have stated that they try to consciously enter this state to conceive the music or films they are working on.
Indeed, as the brain embarks on its long transition from wakefulness and sleep, consciousness can take on unusual qualities. As one example, the painter Salvador Dalí would seat himself in front of a canvas and allow himself to drift off. During states just in between sleep and wake, he would have bizarre hallucinations – and upon snapping back he would paint what he had just seen.
Max Richter is now releasing a 90-minute excerpt of SLEEP, titled SLEEP CIRCLE. It is actually a re-recording with the musicians who performed the piece live. Could this new, shorter version be used to help people fall asleep?
90 minutes is the average length of time between dreams. When you first fall asleep, you enter light sleep, after which you slowly descend into a very deep phase called slow-wave sleep. Then you slowly ascend again until you reach the lightest stage, during which you dream. You go through this cycle multiple times each night. I think a 90 minute piece would be great for launching you into that first cycle, especially for those who get into bed and lie awake on the pillow.
Have you ever tried falling asleep to Max Richter's original eight-and-a-half-hour composition SLEEP?
I do so often; one might almost accuse me of addicted. The first time I was intrigued by the gorgeous details of the composition, so I was consciously listening and paying lots of attention. But by the second time I was able to get swept away in the familiarity, allowing me to sink deeply into sleep. So many people have trouble sleeping, and everyone wants to sleep better. One thing I love so much about Max’s project is its power to help millions, even billions, of people around the world sleep better at night.
Interview by Max Dax
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