"High intensity training for the mind": A neurosurgeon explains why we dream

Plus, are dreams trying to send you a warning about your health?

By Mary Elizabeth Williams

Senior Writer

Published June 15, 2024 9:00AM (EDT)

3D illustration of double bed hovering in air and with white cloud above. ((OsakaWayne Studios / Getty Images))
3D illustration of double bed hovering in air and with white cloud above. ((OsakaWayne Studios / Getty Images))

I woke up exhausted this morning. It’s not that I didn’t get a good sleep — I did. It was just an incredibly busy one, full of running, climbing and at one point flying across a room. As I opened my eyes to the new day, it took a few moments to realize that I had not, in fact, spent a night engaged in intense, impossible physical activity. “Our brains are not resting when we sleep,” explains Rahul Jandial, MD, PhD, whose latest book is “This Is Why You Dream: What Your Sleeping Brain Reveals About Your Waking Life.”

In it, Jandial, a Los Angeles neuroscientist and neurosurgeon, explores why the brain stays active even as the rest of the body is dormant, makes the case for nightmares, unlocks the health signals our sleeping minds may be trying to tell us and reveals the new science of how to potentially give ourselves a more interesting, aware dream life. I talked to Jandial recently via Zoom about the mystical, sometimes “transcendent state” of dreaming, and why you can’t do math when you’re asleep.

This conversation has been edited and condensed for clarity.

You open this book with the evolutionary case for our dreams. Why do we need to dream?

The answer is based on neurodevelopmental biology. The fundamental principle of neurons, neural tissue, is that either you use it or you lose it. When we look at brain activation, brain electricity and glucose utilization, our brains are not resting when we sleep. In fact, the electricity can be seen as equivalent. The question then is, what is going on with the brain activation? Imagination and emotion are being liberated, meaning those neurons are activated. They’re using up glucose, they're sparking electricity through neurotransmitters that typically aren't during waking life. 

"My big theory is that it's high-intensity training for the mind."

My big theory is that it's high-intensity training for the mind so we're not constrained by just the limited parts of our brain we use during the day. It keeps our thinking creative, and it keeps us adaptive as a species. When you look at the waking brain and the dreaming brain, it's quite different areas, and they don't overlap much. My best guess, based on those principles, I think is a new and fresh look to dreaming, that it is not a restful state. It is vibrantly active.

Some of us always remember our dreams and seem to experience them very vividly, while other people say they never dream. They never think about their dreams; they never remember their dreams. Do you think our dreams then are having the same impact on us in relation to our waking selves?

The way to tackle that is to look at the dreaming pattern throughout life. We’ve all had a nightmare, we’ve almost all had an erotic dream at some point. We know what a dream is. They arrive as a universal experience. Clearly, we remember some dreams. Nightmares, in particular, by definition, wake you up and sear you with that memory. I feel like in adulthood we get this variety of dream recall.

"The dreaming brain turning into waking brain is not a crisp moment."

Those people who recall vivid dreams versus those who don't, they have the same brain electricity and the same brain glucose utilization between them. So I think the dreaming process is churning, no matter what the memory. The dream recall varies. And that residue you were talking about is very important. The dreaming brain turning into waking brain is not a crisp moment. There are a few seconds of lingering transitions, called sleep exit. That's an area where you can hold onto a dream memory. People can cultivate this a bit. You can recall your dreams more. Not always, not every time. But just to know that that capacity is there, albeit limited, is fascinating to me. It bookends the sleep entry period, going from waking brain to dreaming brain. There are a few minutes there were people like Salvador Dali said they extracted interesting ideas. So while the recall is variable, the dreaming process is happening robustly in all of us.

I would imagine that there is some correlation around being awakened mid-dream as opposed to awakening in a different sleep cycle.

I didn't find too much about that. Conceivably, a third of our lives is spent dreaming. Towards the end, when we wake up, the dreams tend to be more vivid, the REM cycle also changes. What's fascinating to me about that is that the dreaming process is not something we choose. Sleep is not something we choose. Sleep insists. If you skip a day of sleep. as I did in surgical training, often the next day when you sleep, the REM cycles and the dreaming reports shift to earlier and harder. That's a big statement.

When you're asleep, your body temperature is about the same, a little cooler, the EKG on your heart releases a few sparks that we're familiar with. Inside the skull, it's throbbing with heat, electricity and brain waves. The brain is making us sleep. And what does the brain do when we sleep? It dreams. The most vibrant activity it does is dream. When you look at any system like that, that's not an incidental feature like an appendix. That is a massive process, universally applied across mammals, across other species. I think it's what a collection of neuronal tissue needs to be most adaptive, to be to have that clarity during the day. It's not that the brain is revved down like a computer screen and you click the keyboard and it comes up. It's at that electrical level that dreaming provides the brain a certain rest, almost, that gives us clarity when we wake up. Those are the big concepts that I'm seeing. 

It speaks to an intersection that a lot of us are not always comfortable with. You can't just stay in the science realm here. This is philosophical, what you're talking about here.

When they asked me to prepare this book, I said, “I just need to have one permission — that where there will be gaps of knowledge, I want to say, “I believe. Could it be? I wonder? Wouldn't it be an elegant hypothesis?” I want to be upfront with people. There's no way to say that nightmares arrive in kids to cultivate their sense of self versus other. I can tell you that they arrive at the same time as another capacity called theory of mind, where it becomes, “Somebody smiling doesn't always mean some goodwill for me.” When I put those things together, it's an invitation to people to think about, why do we have to tell Johnny, ’It was only a dream?” That invites the thought that waking thought and dreaming thought before nightmares arrive are blurred. Why do nightmares cluster in families? Falling dreams and teeth falling out dreams don't. I wonder if those universal processes that come through families show where there's a cognitive inheritance, like risk-taking.

To do this as a brain surgeon adds a certain rigor to it. There are people who are dismissed for bringing in feelings of supernatural or transcendent states, and they’re made to sound fringe. What I'm trying to say is, look, lucid dreaming sounds fringe? Lots of science for that. I'm trying to shed light that some of these universal experiences are actually science-based. 

We know that we think differently. Some of us think more in words and some of us don't. Some of us think more visually, some of us don't. It makes me wonder about the ways in which we think in our waking lives are reflected in the way that we process or experience our dreams.

When we look at thousands of dream bank reports, nightmares are universal. Math is very rarely reported. The big major change in the waking brain and the dreaming brain is the executive network, not one spot, but a collection of structures, a symphony that is dampened, allowing for illogical jumps and movie-like scripts. It makes sense with what we know about the dreaming brain’s activation and deactivation. The dreaming brain does not calculate, does not do reason.

[Dreams] tend to be hyper-visual, hyper imaginative. It's a hyper emotional brain at a top speed your waking brain can't get to. That’s why you wake up sometimes with the residue of that feeling, “That just happened.” It starts to make sense why the emotional dreams have a residue. In the dreaming brain/mind, there’s very little calculation. Movement, falling, running feel real, because those neurons in the motor strip are actually firing, generating that electricity we can measure. It's just that they’re not sending the signals down to your body. Dreams are thoughts, experiences from a brain in a different tapestry of activation. That's how people want I want people to think about it. It’s 24 hours in your head. 

And thinking and dreaming are not the same. That's a really important distinction. 

Thinking is directed, with the executive network on task. Adrenaline is up. The dorsolateral prefrontal cortex is looking outward, looking for the signal and the noise. The dreaming brain is executive network dampened, adrenaline dampened. Then your internal imaginative mental workspace is liberated, and that divergent thinking isn't trying to achieve a goal. It's bouncing around. It's ricocheting; it’s making looser associations. And maybe when we wake up, or a week later, we have an aha moment during the day. It's not from the triple espresso. It's from this dreaming process that is loosening the associations by design. I think that's the most romantic, big way of thinking of it.

Let's talk about nightmares. You talk in the book about the purpose that dreams can serve us, and you make that distinction between people who are processing PTSD and the kinds of nightmares that all of us experience day to day. Why do we have nightmares?

Big question. When I was telling people I was writing a book on dreams and dreaming, the first thing they were asking was, “Surely nightmares have to be a glitch or a mistake?” 

Nightmares can be understood by breaking them down into age groups, pediatric and adult. Pediatric ones arrive universally. They may cultivate the sense of self versus other. They prompt us to teach our children that what you're thinking and experiencing in this state is not reality. That's a big thing to teach kids, and then they almost always fade. There are very few nightmare disorders in children. To me nightmares in children are cultivating the mind in some way. They arrive and they dissipate over a pattern of a few years.

In adults, they can come in PTSD flashbacks, which is a bad experience memory on a loop. Then there's the adult nightmare that occasionally happens. It's a byproduct I think of the imagination network. The lessons that I found there are that for people who don't have nightmares, if new nightmares arrive, they're persistent, they get worse, that's something to pay attention to. Nightmares there may be the warning signs for things, like they are for Parkinson’s. There are literature studies coming out for lupus and autoimmune diseases. The first alarm is a change in the dreaming pattern, specifically nightmares. 

Nightmares serve a function in children. In adults, that may be our earliest warning bell for some changes that are happening. Not always, but potentially. I would say maybe they should be considered a vital sign like temperature, blood pressure, something that something that patients should report, particularly in the mental health space. 

You talk in the book about how not just nightmares, but dreams in general can be telling us something about our health. We don't talk to our doctors about this. 

Until now. Now we know dreams are not random. They're our brains in a different mode. Dreams are a knock on the window from our hyper-emotional, hyper-imaginative brain state. That doesn't mean every dream has to make sense. They're going to be symbolic. They're not rational. But dreams are a fundamental process. So the next dream I have, I might not be so quick to forget it or think it's completely insignificant.  

You talk about lucid dreaming, and how small a percentage of people, it seems, can actually really do it. But all of us can do things to maybe have a more pleasant experience when we close our eyes at night. What’s going on, and what are the limitations? 

The best example for that is something called imagery rehearsal therapy, rescripting your nightmares. Even if that happens only occasionally and only in some people, what a concept, that you can redirect the product of your imagination, that you're not just a victim of your nightmares, and that reimagining can actually change the electricity and the neurotransmitters and the pharmacy of your own brain. 

Lucid dreaming is interesting. To be clear, lucid dreaming is the return of awareness within a dream, not asleep entry, not asleep exit. The most rigorous science by dreaming is actually about lucid dreaming. Here's what I’ve found — consistent reports show a third of people do it. It doesn't mean all night long, it’s a fragile state.

Here are four quick tidbits of proof on it. With surface electrodes, we can prove if somebody's asleep, you can't fake that. People go to sleep labs and use left-right, left-right eye communication to communicate wirelessly. Then there's Galantamine, an acetylcholine drug for dementia. Patients who take come in saying they're lucid dreaming. If we double the dose, they're lucid dreaming more. Dose-dependent escalation shows cause and effect, and that it's a biochemical process. You take a pill, and you lucid dream more, so it's not just reporting. The third thing is that people in the scanner show that [in lucid dreaming] the executive network comes back online a little bit, because people are starting to do Morse code eye movements to do simple math. As a little bit of awareness comes in within your dream, a little bit of math capacity seems to come back. That’s strong science storytellingt. And then the last piece is with the left-right eye method to cultivate lucid dreaming, the one that's called MILD. They had a bunch of people use the technique, come into the sleep lab and prove with their eye movements that they could lucid dream more. It reminds us all that's not crisp — awake, asleep, awake, asleep.

How has writing this book and doing this research changed how you look at your own dream life, and how you understand dreaming? 

The exploration of dreaming left me with things that were revelatory. Sleep entry and sleep exit are the application that I can extract better ideas, more creative ideas. Sleep entry, I can extend it. Sleep exit, I always wake up slowly and try not to go on Instagram and write a few notes. I know there's an interesting way of thinking I have there. I get a lot of ideas that sleep exit — good ones and bad ones — but that's really my idea generator.

That said, two other revelatory things. One is dream enactment behavior. Men in their fifties, if they act out their dreams, almost invariably develop Parkinson's later. The physical withering of the brain and mind, its first warning flare is a changing dreaming pattern. Within that, please look up paradoxical kinesis. When people have Parkinson's and their movements are rigid and the speech is stifled, and they act out their dream, their movements are fluid and their speech is loud and clear. The dreaming mind in Parkinson's removes the physical symptoms of the body. That makes no sense. 

The second thing is that the one or two minutes after our heart stops, that last gush of blood in our carotids and vertebral to our brain, the brain doesn't whimper to death, like a liver or a heart. The brain with that last gush of blood somehow knows. It explodes with neurotransmitters, and a burst of electrical brainwaves that look like a massive dream and memory recall. That's a measurement. We've got people whose hearts show nothing one minute afterwards. Measurements. That's not my opinion. That explosion of brainwaves happens in the minute or two after the cessation of electrical activity on EKG. How beautiful is that? That our brain’s last act is to go out with a salvo of experience and emotion and feeling?


By Mary Elizabeth Williams

Mary Elizabeth Williams is a senior writer for Salon and author of "A Series of Catastrophes & Miracles."

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