Visit Your Local PBS Station PBS Home PBS Home Programs A-Z TV Schedules Watch Video Donate Shop PBS Search PBS

Dreams: Expert Q&A

  • Posted 11.30.09
  • NOVA

On November 30, 2009, Robert Stickgold graciously answered dozens of wide-ranging questions about dreams and sleep.

Robert Stickgold

Robert Stickgold

Robert Stickgold is an associate professor of psychiatry at Beth Israel Deaconess Medical Center and Harvard Medical School as well as director of the Center for Sleep and Cognition. Full Bio

Photo credit: Courtesy Robert Stickgold

Robert Stickgold

Robert Stickgold is an associate professor of psychiatry at Beth Israel Deaconess Medical Center and Harvard Medical School as well as director of the Center for Sleep and Cognition. He received his B.A. from Harvard University and his Ph.D. from the University of Wisconsin, Madison, both in biochemistry. His current work looks at the nature and function of sleep and dreams from a cognitive neuroscience perspective, with an emphasis on the role of sleep and dreams in memory consolidation and integration. In addition to studying the normal functioning of sleep, he investigates alterations in sleep-dependent memory consolidation in a range of neurological and psychiatric conditions, including schizophrenia, bipolar disorder, Parkinson's disease, cocaine addiction, PTSD, insomnia, and sleep apnea. Stickgold has published over 100 scientific articles and two science fiction novels.

Q: Is there any truth to dreams being a window to our "unconscious"? Perhaps the question should be: What level of consciousness is expressed in our dreams? Do they "represent" anything of our feelings, moods, attitudes?
Jose Lopez, Brooklyn, New York

Q: Are Freud's teachings on dreaming still valid amongst new scientific findings?
Anonymous

Robert Stickgold: Answering these two together, I'd say that Freud was probably 50 percent right and 100 percent wrong! He made very good observations of dreaming, but he tried way too hard to fit them into a model that shows little likelihood of being correct.

Having said that, dreams can act as a window to our unconscious. In the most extreme example, we did a study with amnesiacs who would report dreams about pre-sleep activities (playing Tetris!) that they had no conscious memory of. But more generally, I think our dreams are constructed within networks of associated memories that we do not normally access directly, and which therefore might reflect feelings, moods, and attitudes that we don't normally have direct conscious access to.

Having said that, I think that dreaming also is looking for new ways to connect these associative networks, and it isn't a problem for the brain if some or even most of these explorations end up being useless or blatantly wrong. So it's far from a sure bet that a connection or action contemplated or carried out in a dream is one that actually fits with your feelings and beliefs.

Q: It has been suggested that dreams are therapeutic—therapeutic in that dreams help solve emotional conflicts. How does this work?
Jerry Gifford, Murfreesboro, Tennessee

Stickgold: There are two versions of this question. From a psychoanalytic (e.g., Freudian) perspective, the act of remembering dreams in the morning, and then trying to understand the emotional issues that seem connected to them, can help you understand emotional conflicts better. From this perspective, you are using the dream sort of like a personalized Rorschach test, helping you identify emotional conflicts that you might not have been aware of consciously.

From a more cognitive neuroscience perspective, emotional conflicts are simply one of the realms of memories that are processed while we sleep and dream, largely outside of intent or conscious awareness. From this perspective, sleep permits a time when the brain can search for and identify useful associations between recently formed emotional memories and older ones, helping to place them in a more useful context, from which their resolution may become more readily apparent.

Q: People say that dreams are just reflections of what we think about the most during the day. Is that true?
Tashi Paljor, Toronto, Ontario

Stickgold: No. Dreams seem to be more about what the brain calculates as most important. Arguably, this can be what you spent most of the day thinking about, but it need not. A simple example would be an unexpected but very emotional event occurring shortly before you go to bed. You're much more likely to dream about that than the four hours you spent, say, weeding the lawn. Now you could argue that you are thinking about more important things while weeding, but that brings it back to being about what's important.

Having said that, it's also undoubtedly true that anything you spend a lot of time thinking about during the day will be likely to be interpreted by your brain as important simply because you spent so much time thinking about it. But I suspect it's something like the importance multiplied by the time spent on it that determines what we dream about.

Q: Would documenting one's dreams help one better manage their real life?
Paula, San Jose, California

Stickgold: Maybe. But only insofar as they give you a sense of what kinds of issues and concerns repeatedly show up. It's probably better than reading your horoscope in the paper.

Q: Hi, I am 60 years old, and I have had hundreds of lucid dreams over the last 30 years. Often I transition into a lucid dream from an "ordinary" dream. Does your theory incorporate lucid dreams and attempt to account for their occurrence?
Francis Louis Szot, Boca Raton, Florida

Stickgold: We don't know how to incorporate lucid dreaming into our models. Lucid dreaming, which involves being aware of the fact that you're dreaming while you dream, appears to be a state between REM sleep and waking. Regions of the prefrontal cortex, which control logical reasoning and executive decision-making and which are normally turned off during REM sleep, appear to be turned back on. This allows some lucid dreamers to gain partial control over the events in their dreams. But whether this would actually impair the normally automatic processing of memories, or instead allow the dreamer to control the memories to be processed is totally unknown. Check back in five years!

Q: Has there been any documented research conducted by reputable sleep study groups concerning lucidity and dream control. I found a great website that goes into some detail concerning this subject. I am curious as to what the experts in the field of dream study think of this idea (i.e. is this for real, or just bunk?). http://www.dreamviews.com/index.php
Thanks.
Anonymous

Q: Does anything physiological happen in the sleeping brain to cause a lucid dream (a dream in which you realize you are dreaming)?
Jon Medders, Fayetteville, Arkansas

Stickgold: Lucid dreaming is absolutely real. Steven LaBerge, from Stanford, has been the single biggest researcher in the field (http://www.world-of-lucid-dreaming.com), although some feel he has become overly committed to its value.

A recent article in the journal Sleep shows that lucid dreaming is accompanied by an increased activation of brain regions that are normally suppressed during sleep and that control rational thinking and executive control. Just such a link had been predicted by many people for years, so these findings support the notion that lucid dreaming represents a brain state somewhere between normal REM sleep and wake.

Q: Sometimes when I dream, I actually know that I am dreaming. So I try to do things that might be impossible in real life, such as flying. I just think about it really hard, and I jump in the air and I start flying. I would say that this happens in at least half of my dreams. Also, when I know that I am dreaming and it happens to be a nightmare then I try to wake myself up by closing my eyes and just hoping that when I open them I am awake. Why do I know that I am dreaming when I am having a dream?
Desert Oasis High School 11th grade, Las Vegas, Nevada

Stickgold: This is known as lucid dreaming, and represents a state where some parts of your brain have returned closer to a waking state and hence can detect the fact that you're actually dreaming. It's an interesting fact that people who can manipulate their dreams when they become lucid choose to try to fly rather than trying to imagine other activities that you might expect them to try!

Q: I, and people I have asked, used to dream about flying (being able to lift off the ground, etc.) quite often, but don't seem to have those types of dreams any more. Is there a scientific explanation for "flying dreams" and their frequency of occurrence?
Jess Porter Abate, Boston, Massachusetts

Stickgold: Allan Hobson has suggested that this is an example of the brain trying to figure out what's going on. In our dreams, we are almost always "in motion." But in reality, our bodies are lying in bed, motionless. At the same time that the dreaming brain is constructing the illusion of movement, it's also getting feedback from the body that we're not, in fact, moving any muscles. Flying might be one way that the brain can put this together—we're moving, but our limbs aren't bending and moving.

Q: I was head-injured in the 1980s and stopped dreaming. I also had no short-term memory. When my memory improved, I started dreaming. I thought I had been dreaming but not remembering them. Was I really not dreaming?
Brian Trotter, Metairie, Louisiana

Stickgold: Good question! Damage to some parts of the brain does seem to stop dreaming altogether, but not usually damage to those regions involved in short-term memory. So if I had to guess, I'd say you were still dreaming and simply not remembering the dreams.

Q: I recently asked Dr. William Dement at Stanford University why dream memories fade almost as soon as we stop dreaming. He said that research hasn't answered this question yet, but his best guess was that if we were to remember all our dreams, we might not be able to easily distinguish dreams from memories, and that might impede our functioning in waking life. This makes sense to me, but I was wondering if there were other hypotheses or any current research on this topic?
Terry Ehret, Petaluma, California

Stickgold: I suspect that you and Dr. Dement were using different meanings of the word "why." Dement likely was talking about why we might have evolved to not remember them, and I'd tend to agree with him. We probably dream, in one form or another, for six out of eight hours each night. I'd hate to have all of those memories hanging around! But the other "why" has to do with the memory systems that either actively cause us to forget our dreams or, more likely, that fail to effectively store them.

One theory is that the shutting off of noradrenaline release during REM sleep may, in turn, shut down systems that normally encode memories. When we wake up, our most recent dream appears to be held in some sort of short-term buffer; since noradrenaline release turns back on when we wake up, if we rehearse that dream in our mind after waking, it may then become more effectively stored with the help of the newly activated noradrenergic system.

There is, however, another possibility, which is that memories of our dreams are formed, but that we don't know how to "find" them. We usually access recent memories by remembering, for example, what happened before it, or where we were or who we were with, but we don't have those cues for recalling dreams. The reason I take this possibility seriously is because almost everyone has had the experience of having something happen during the day—a cat running out into the street, for example—and then suddenly remembering a dream from the night before involving a cat. It thus appears that at least some dreams are stored without our ever realizing it.

Q: I assume I am dreaming each night, so why do I seldom recall any of my dreams?
Susan Majerus, West Des Moines, Iowa

Stickgold: I would predict that you're a sound sleeper and wake up with an alarm clock. Those are the biggest obstacles to dream recall. Since we only seem to remember dreams from the period shortly before we awaken, someone who wakes up a half dozen times during the night is much more likely to remember a dream than someone who sleeps straight through 'til morning. Then, in the morning, recall is optimal if you wake from REM sleep, and an alarm cuts the chance of that about in half, since we're in REM no more than half of the time in the morning. In addition, studies have shown that any sensory input or moving around when you wake up will tend to wipe out your dream memories. So an alarm clock gives a big sensory input, and you usually leap up to turn it off.

Q: What can I do to remember my dreams when I wake up? Is it possible I don't have dreams? If I do dream, what can I do to remember dreams?
Anonymous

Stickgold: I tell people that the best way to remember some dreams is to drink four large glasses of water before bed. This will cause you to wake up repeatedly during the night, and the most likely times will be at the ends of periods of REM sleep, when you are most likely to be dreaming intensely. Almost everyone who reports "no dreaming" will recall dreams when awakened from REM sleep.

Q: Is it true that the only way one can remember dreams is if one wakes up in the middle of them?
Anonymous

Stickgold: I suspect that this is at least close to the truth. Although we're not really sure, I'd guess 95 percent of your dream recall is from dreams that occurred within 10 minutes of when you awoke.

Q: How can I train myself to remember more of my dreams?
Anonymous

Stickgold: It always embarrasses me to say so, but if you repeat to yourself "I'm going to remember my dreams tonight" three or four times before going to bed, it seems to help over a couple of weeks. You can also turn off your alarm clock and allow yourself to wake up naturally. That seems to help as well. If the problem is that you wake up with dreams in your mind and then forget them, you want to try to lay quietly in bed, preferably without moving at all, and with your eyes still closed, and try to recreate as much of the dream as you can in your mind. By rehearsing it after you wake up and before you let other sensations enter your mind, you can encode them in a form that is more stable.

Q: How can normal sleep and breathing during sleep be restored after SSRI use? Many people are complaining (on patient forums like paxilprogress.org) of sleep apnea, jolting awake and struggling to breathe, insomnia, and other sleep disturbances after taking or withdrawing from SSRIs. Is sleep disturbance responsible for SSRI-related memory/brain-fog problems? There have been only a few medical journal articles addressing the SSRI/apnea connection. (Google "Onset of Obstructive Sleep Apnea after Initiation of Psychotropic Agents.") Many doctors seem to be unaware of this connection. Please address how SSRIs affect sleep and memory, and how to restore normal sleep, breathing, and memory after SSRI use. I will be very grateful for any insight, and I look forward to your response.
Anonymous

Stickgold: I doubt very much that SSRIs can directly cause obstructive sleep apnea. The Google search you suggested offered one case of an individual who put on 35 lbs after starting SSRI treatment. Whether a consequence of the SSRIs or not, putting on that much weight can definitely cause sleep apnea, since excessive fat in the neck is a major contributor to the airway collapse that produces the breathing problems during sleep.

Q: Hello,

I very much enjoyed your segment on the "What Are Dreams" episode, Dr. Stickgold.

I am a recently diagnosed sleep apnea patient and began CPAP treatment about a month ago. Therapy is going very well. I adapted to the equipment quickly, am sleeping well, and feel great during the day. My energy, concentration and cognitive abilities are much improved already.

During my initial sleep study (no CPAP), my Stage 3-4 sleep was only 10 percent of total sleep time, and REM sleep was only 6.7 percent. I slept just under 5 hours that night.

I have had little to no dream recall for at least several years. Any idea when (and if) this may return? Is it likely that I am actually dreaming but don't remember? I used to recall dreams nearly every night and I miss it!

Thanks!
Anonymous

Stickgold: You are almost certainly still dreaming. The most likely reasons for not remembering them are that you're sleeping more soundly and hence not waking up during the night (when you obviously could remember dreaming), and that the CPAP machine is so distracting when you wake up that the noise of the machine, the physical sensation of its being on your face, and the process of taking it off all compete with a normally weak dream memory and cause it to fade before you can remember it.

Q: I've read that nightmares and sleep disturbances are linked to higher suicide risk. If a person is suffering depression and having nightmares, what do you suggest might minimize that risk? Are sleeping pills useful to modify dream patterns, or what else do you recommend? Any comments on links between nightmares/dreams and suicide risk are welcome. Thanks for the opportunity to ask.
Sandra, Vancouver, Canada

Stickgold: If there is an association between nightmares and suicide risk, I doubt that it's that the nightmares increase the risk of suicide. Rather, they would be an indicator of the psychiatric condition that is the source of the suicide risk. If the dreams are related to PTSD, there is evidence that the prescription drug Prazosin can reduce their frequency or even eliminate them altogether. On the other hand, inadequate sleep can almost definitely contribute to depression, and thereby increase suicidality. Sleeping pills per se is not something I'd recommend for treating nightmares. You might also look into methods of changing your nightmares. An article by Margaret Talbot in the November 16 issue of The New Yorker describes this process.

Q: I am a psychologist who has worked with patient dreams for many years. I found the assertion that nightmares during REM sleep are creative attempts to work out fears about the future to be interesting but perplexing. It that were true, wouldn't our nightmares have better resolutions? Instead, we are generally left with unsettling emotions that may serve to render us helpless rather than enable us to feel mastery. I wonder whether another purpose of nightmares, which would help explain this dilemma, is our impulse to talk about our disturbing dreams with others we judge to be helpful. After all, we are social beings, who have been encouraged to discuss and work out dreams in many diverse ways: with social groups, parents, and therapists.
Dr. Barbara Barak, Great Neck, New York

Stickgold: There's a big debate over whether nightmares are functional or dysfunctional. Personally, I'm in the dysfunctional camp. Sorry, I mean I'm in the camp that thinks that nightmares are dysfunctional! Tony Zadra is a Canadian dream researcher who has worked extensively with nightmare sufferers to help them change the outcomes of the dreams. The article by Margaret Talbot in the November 16 issue of The New Yorker describes his work. But there are others who feel equally strongly that they have evolved to help us prepare for possible threats.

Q: What are the most practical pieces of advice that you can give based on strong data and corroborated findings from multiple studies relative to sleep's effect on memory and problem solving?
Scott Isebrand, New York, New York

Stickgold: Get enough sleep! That's probably the most valuable thing you can do. It might help to review some of these problems before going to sleep, but we don't really have data to show that this actually helps. But if you need an alarm clock to wake up, if you're drinking coffee in the morning to get your brain working, or if you find that you sleep longer on the weekends that on workdays, you're not getting enough sleep!

Q: I am curious about the effects of sleeping drugs such as Ambien on the sleep cycles. Thanks!
Anonymous

Stickgold: In general, these drugs act to reduce both the percentage of time spent in REM sleep and the percent spent in deep slow-wave sleep. Insofar as it decreases REM time, it will tend to decrease the amount of this more intense dreaming.

Q: In an age of Ambien and Lunesta, when the long-term consequences of taking sleep medication are not fully known, what can you say about sleep and prescription sleep aides? Are they potentially dangerous? Do you believe many Americans are overly dependent on them? What might be the consequences (if any) on cognitive performance and memory as a result of long-term use?
Anonymous

Stickgold: This is a big hairy problem. The short answer is we don't really know. I suspect there are millions of Americans using sleep medications who would do better with a short course on cognitive behavioral techniques to help you sleep better without medication. But there are also a large number of people who receive great benefit from them. Most of these drugs, unfortunately, alter the structure of your sleep, and not in obviously beneficial ways. How this impacts the kinds of memory processing that we believe occur during sleep is an open question.

Q: In dreams, is the brain operating outside of the "self" construct that forms our identity?
Clark Martin, Vancouver, Washington

Stickgold: Certainly not "outside" of our self construct, but certainly with a lot less respect for it! We clearly do things in our dreams that we would never consider doing in waking, and that are contrary to our sense of self. This problem has plagued philosophers for centuries! On some level, our brains understand better than we do that these are just dreams, and that they can explore possibilities that we would never seriously consider during wake without putting us or our friends and family at any risk.

Q: Why do so many people have a reoccurring dream, especially in the pre-adolescence years?
John Barry, Adams, Massachusetts

Stickgold: I don't know that they're any more common in pre-adolescence than later on! But I also don't know why we have them. Most of them seem to revolve around anxiety-producing topics that have come up over and over in our lives. Hence dreams about exams, or missing plane tickets, or being in school without our clothes on. I suspect we don't appreciate how anxious we've been around these issues. But our brains detect their repeated nature, and I think that flags them as important topics in need of further processing while we sleep.

Q: I would like to know why I have an ability to wake myself up from scary dreams. Since I was little I have had two types of recurring dreams. The first I call "dreams within dreams." I am usually in a dark room with a shadow person coming after me. In the dream I begin to tell myself to "wake up" repeatedly until I wake up. Things seem better, but then the dream begins to happen again, and I realize I am still asleep. The pattern repeats until I eventually wake myself up.

The second instance happens immediately after falling asleep, when you feel like you are falling and "jolt" awake. The dreams are either something pulling me under the bed, or someone creeping up to the bed. I also say "wake up" to myself in these dreams until I finally do, or I dig my nails into my palms until I wake up.

What does this mean? I would love to know. I tell people about these dreams and they look at me like I am crazy! Thank you!!
Melissa Lujan, Portland, Oregon

Stickgold: There are two very different stories here. The "jolting awake" immediately after you fall asleep (these are called hypnagogic dreams) occurs because just as you fall asleep you enter a stage of light sleep that is in many ways similar to REM sleep, but misses one important piece. This is a brain mechanism that prevents you from acting out your dreams. Since this doesn't happen at sleep onset, when you feel a need to move quickly in a hypnagogic dream you actually make the movement, and this can jolt you awake.

The explanation of the second piece, about trying to wake yourself up from within a bad dream, is less clear. It appears that what happens is that the anxiety or fear experienced in the dream begins to awaken you, and then, as in a lucid dream, you can become aware of the fact that you're dreaming. How you then do wake yourself up (or, alas, only dream that you did!) is still a mystery.

Q: I have gotten used to sleeping with the radio on (BBC via NPR). I seem to fall asleep easily (maybe even more easily) like this. I believe that I sleep well, but sometimes I wake up when a subject of major interest comes up—generally science related. The brain is therefore somewhat "tuned in." Does this interrupt or otherwise interfere with the various brain activities that should be going on?
George L., Reading, Pennsylvania

Stickgold: If you must have the radio or TV on to fall asleep, get a timer that will automatically shut it off after, say 15 minutes, one that you can keep cranking back up until you fall asleep. Having a radio or TV on leads to constant interruptions of your sleep, most of which you probably don't remember in the morning. But it's bad, bad, bad.

Q: What are the similarities and differences (e.g. brainwave patterns, overall physiology) between deep dreamless sleep and the state of deep meditation, and if they are the same, would this be considered a separate state of consciousness?
Anonymous

Stickgold: Sleep and meditation appear to be very different brain states. If anything, the brainwave patterns of mediation look more like light sleep than deep sleep.

Q: It seems to me that there has to be an evolutionary reason for why we have dreams. Have they been necessary for survival? And I wonder if perhaps they serve as a means of ordering our experiences as to their importance in our own personal survival. Are dreams just a way of presenting random scenarios to us to gauge our reactions and to order our memories accordingly?
Marty, Portland, Oregon

Stickgold: I think I'd say "all of the above." But remember, dreaming is very different from remembering dreams. I would guess that even really good dream recallers remember less than 10 or 15 percent of their dreams from a night. Whatever purpose they serve must not require that we remember them afterward.

Q: I commonly dream (especially when napping, but not always) that I am unable to move or speak. It is incredibly terrifying. What causes this? Could these dreams actually be a symptom (e.g., hallucination) of sleep paralysis? Also, I have epilepsy, and sometimes experience vocal paralysis while seizing. Could I be seizing when I have nightmares that involve the inability to move or speak?
Virginia Richardson, Richmond, Virginia

Stickgold: Not likely. REM sleep produces a paralysis of the body that is critical for preventing you from acting out your dreams in your sleep. REM sleep behavior disorder, which is a medical condition where this paralysis breaks down, can lead to serious injury to you or your bed partner. Sleep paralysis is the phenomenon where you only half wake from REM sleep and the paralysis has not yet turned off. Richard McNally has suggested that what some people believe to be alien abductions are, in fact, instances of sleep paralysis.

There's nothing dangerous about sleep paralysis, and it doesn't seem to be an indicator of anything worse than sleep deprivation. But chronically getting less sleep than you need is one likely cause of it; more sleep will then reverse it.

Having said all this, you don't seem to be describing sleep paralysis, but a "freezing" within your dreams. This is something that is commonly experienced by people in their dreams. Allan Hobson has argued that it simply reflects your brain's confusion about the fact that the feedback it's getting from your body while you dream is that, despite what your dream hallucination suggests, your body isn't moving at all. Others would argue that it reflects a real tendency of people (and other animals) to freeze in moments of extreme terror. In any case, I don't think there's anything of concern in having such dreams.

Q: Dr. Stickgold,
I have had a strange experience while sleeping that I was hoping you may have a scientific explanation for. I was sleeping quite soundly during the day, and I woke up (eyes open, and consciously thinking) but I could not move my body, as if I was paralyzed. After I realized that I was not able to move, I couldn't really do anything besides go back to sleep. Is this a common phenomenon? Did I wake up in REM sleep?
Thank you,
Melissa, Cleveland, Ohio

Q: As an adolescent, I would wake up but my body would not "wake up" or move. I was unable to move for 20-60 minutes. I could see but not talk or move. After a few minutes, I was able to whisper. If I was lucky, I would catch the attention of my sister and ask her to move my body. This would be the only way my body would wake up. If I was unlucky, I would just go back to sleep and hope for full movement when I woke up. What was happening to me? Also, no-one believes me. Thank you!
Chelsea, Austin, Texas

Stickgold: This is a condition known as sleep paralysis. As I noted in the answer above, REM sleep produces a paralysis of the body that is critical for preventing you from acting out your dreams in your sleep. (See above for more details.)

Because you're kind of stuck between REM sleep and wake, sleep paralysis is often accompanied by waking dreams, where you might see someone come into your bedroom, or giant spiders on the wall. But since your eyes are open and you're largely awake, these dreams are seen as happening in your bedroom, while you're lying there paralyzed!

Q: In dreams we see and hear and feel as we do through our senses in the real world. Do our dreams use the same centers in our brains that our senses use?
Randy Grenier, Waltham, Massachusetts

Stickgold: Absolutely. This might be why need to "disconnect" from the outside world when we sleep, so these brain centers will be available for replaying memories and imagining new scenarios.

Q: How are depression and insomnia linked? Or why is depression linked to insomnia?
Baiba Caunite, Lakewood, Ohio

Stickgold: It looks like the two are linked in a vicious circle. Inadequate sleep appears to at least increase the likelihood of depression, and depression then increases the likelihood of insomnia.

Q: Why do I have strong memories of past and long past dreams whenever I trim my nails?
James Boyer, Canada

Stickgold: I have absolutely no idea! I've never heard of anything like this. I hope it's pleasurable!

Q: Why is time different in dreams? For instance, I can have a dream that in "real life" would take hours to occur (the events in the dream), and yet I am only asleep for 10 minutes?
Anonymous

Stickgold: We don't have an answer to this one. I did one study asking people how long their dreams seemed to last, and got answers ranging from 5-10 seconds to 10 hours! Matt Wilson, who records brain activity in rats, has shown that the brain seems to replay memories at close to normal speed in REM sleep, but it can run them speeded up 100-fold during non-REM sleep. Maybe this is part of the story.

Q: Why do scientists believe people work on problems during sleep that they could not solve when they were awake? Is it because sometimes one wakes-up with a solution without starting to work on the problem again the next day?
John M. Sanders, Las Cruces, New Mexico

Stickgold: That's one reason. I've asked people from all around the world, and every language has some form of the expression "sleeping on a problem." But we've also been able to show it directly by giving people problems that they don't solve at first and then seeing whether a daytime spent awake or a night of sleep is better for coming to a solution. So far, three separate laboratories have concluded that sleep increases your ability to finish solving an outstanding problem.

Q: I never say anything in my dreams. Why?
Niki Robertson, Raleigh, North Carolina

Stickgold: No idea! Unless you mean that you seem to speak without actually making sounds. This is quite common. I guess some psychologists would say it means something, but I certainly wouldn't know what. It might be that you're so talkative during waking that your brain is toying with what it's like to not talk so much. Or it could be that it reflects an obvious daytime shyness. Or it could be any of a hundred other things.

Q: Mr. Stickgold,
After watching the NOVA program on dreams last night, I was left with a number of questions.

I am a painter and sculptor and sometimes dream that I am doing that work. Upon waking, I often attempt to capture some of the solutions I arrived at during the night. Some apply and some do not. My current body of work explores the experience of thought, especially concerning difficult problem solving. In many ways it is similar to the dream state where disparate elements are juggled in an attempt to come to a conclusion or resolution.

I have also become aware that narcolepsy, a condition that seems to run in my family, is attributed to a preponderance of REM sleep. Although not personally diagnosed, I do find that I seem to begin to dream almost before I fall asleep and sometimes feel as though I dream almost all through the night, waking from dreams four, five, or six times during a night.

My question is this: Has there been any evidence that links the creative arts with narcolepsy? Are artists, inventors, and architects and the like just borderline or closet narcoleptics?
Roger Rapp, Pine, Colorado

Stickgold: This is a fascinating question. I know of no evidence linking narcolepsy to creativity, but I certainly would not rule out the possibility. Your comment of beginning to dream "almost before" you fall asleep is actually normal. We've studied these "hypnagogic" (sleep onset) dreams, and they can clearly "start" before you're "fully" asleep. (Both of these terms are a little loose in their definition.) Many of the famous examples of scientists dreaming solutions appear to be from this period, and Thomas Edison had a whole technique for waking himself up just as he fell asleep, precisely so he could remember these thoughts and images, many of which he found useful in solving problems.

Your sense of dreaming all night long is most likely related to your awakening so often, and not vice versa. I personally often awaken two or three times to go to the bathroom, and I normally remember dreams each time. It turns out that the end of REM periods is one where it's particularly easy to awaken, so if you're going to wake up, it's likely to be from a period of dreaming.

Q: Dr. Stickgold,

Would you comment on these brief overall statements? It strikes me that dreams are so complex (and random) that it is generally almost impossible to distinguish worthwhile salient points from fantasy and sheer play. Dreams are by nature uncollated and illogical; the admixture of emotions and images are overlaid on one another in a mental palimpsest which utterly defies empirical analysis. Just my opinion based on my own non-waking experience.
Tom Horn, Austin, Texas

Stickgold: There's some truth in what you say. But I think you're being too harsh. For example, I would say that dreams are more chaotic than random. By chaotic, I mean that the rules governing their construction are too complex to understand easily. Thus, while dreams are illogical from a waking perspective, they probably follow rules of their own. For example, we know that various forms of intense waking activity can predictably effect dream content, if only statistically. Furthermore, the form that these waking activities take can be very stereotypical from one person to the next.

I'd also suggest that your distinction between "salient points" and "fantasy and sheer play" is not a legitimate one. I would say that fantasy and sheer play are often reflections of important issues in our lives, and may be one mechanism by which the brain attempts to understand the nature of their importance.

Q: How would you explain that what I dream comes to pass either that day when I get up or the next day?
Pamela, Houston, Texas

Stickgold: Sigh. I have three possible explanations for this. The first is that humans are very poor at statistics, and that random coincidences are almost always taken as being meaningful. (In fact, this is a great advantage, because it is the basic mechanism by which we discover causal relationships. We just seem to overdo it.) For example, if the average person has three or four dreams a year about something bad happening to one of their parents, then about one person out of 25 will have such a dream within a couple of days before the death of one of their parents. Even when there seem to be details that match, the odds of such matches occurring by chance are much, much higher than most people expect. (Probably the best example is the fact that if you have 23 people in a room, there's a 50:50 chance that two of them will have the same birthday.) Another part of this explanation is that we will often call two things a match when, in reality, most everything about them is different, but a few most important features match. Again, this leads to a misestimate of the likelihood of this occurring by coincidence.

The second explanation is that it's not a coincidence, but reflects a nonconscious calculation by your dreaming brain. It's a variant of the question, how come when I think my wife's going to be angry at me for forgetting to do something, she often is? Thus, you might unconsciously have picked up indications about someone's health or feeling on a topic, and then dreamed about it. When it turns out to be right, we're always struck by this predictive power of dreams.

The third explanation is what I call the "woo-woo" explanation, which is that the universe doesn't work the way mainstream science (myself included) thinks it does, and that dreams have a magical access to the future. For this to be true, many of the most fundamental laws of nature that scientists have discovered would have to be wrong. But this has happened at least twice in the last hundred years (relativity and quantum mechanics), so there's a reasonable likelihood that it's going to happen again. Having said that, I don't personally take this possibility seriously, because there haven't been any well-documented cases of someone, like you, being able to do this in a way that can't be explained by one of my first two explanations.

Q: I am a counselor at a university counseling center. Many of the students I see believe in the power and reality of "prophetic" dreams. What does science have to say about such dreams?
Anonymous

Stickgold: See my answer to Pamela, above.

Q: A few years ago, after a few scary and violent sleep incidences, I was diagnosed with a REM sleep disorder. I am presently on medication to control it, but I was wondering what the latest thinking was for long-term prognosis?
Anonymous

Stickgold: If you are referring to REM sleep behavior disorder, where you physically act out your dreams while still awake, possibly attacking and even injuring a bed partner or fleeing from a dreamed danger and injuring yourself, there is now evidence that you are more likely than average to develop Parkinson's disease in the future. It would be worth talking with your physician or a neurologist about these risks.

Q: What is the "deal" with screaming nightmares? I have been known to talk in my sleep, but I on a rare occasion wake-up screaming. This usually accompanies a very stressful time or a period of exhaustion. What is the relationship? Thanks for settling this life-long question!
Anonymous

Stickgold: I'm afraid I can't add much to what you've already said. It probably involves waking up without a clear awareness that you were dreaming, and periods of stress and exhaustion would likely increase the likelihood of this happening.

Q: How does alcohol affect non-REM and REM dreams and the sleep cycle?
Ken Russell, Portland, Oregon

Stickgold: Alcohol can help you fall asleep faster, but the good news stops there. Alcohol suppresses REM sleep, so your night will start out without any. But as the alcohol is broken down, half-way through the night, you will start to wake up and have difficulty falling back asleep. When you do, you're likely to have a "REM rebound," where your brain tries to make up for the REM it missed early on, and this can lead to unusually unpleasant dreams. All in all, it's bad for your sleep and a bad way to try to deal with insomnia.

Q: How much has the human imagination been studied, and what relationship does the imagination have with dreaming? In other words, when we use our imagination, are we doing anything similar to dreaming? What implications would there be if we found a connection between using our conscious imagination versus our subconscious dreaming?
Evan Quinto, Fairfax, Virginia

Stickgold: While dreaming surely qualifies as a kind of imagination, it's very different from our waking imagination. In REM sleep, where the most intense dreaming occurs, the physiology of the brain is very different from waking. For example, the hippocampus is a brain structure absolutely necessary for recalling recent events from memory, but the outflow of the hippocampus is almost entirely shut down in REM sleep, which might be why we so rarely dream something that actually happened. Another region that's shut down during REM sleep (going by the rather ugly name of dorsolateral prefrontal cortex) is normally responsible for logical reasoning, so this feature also fails during dreaming. This region is also responsible for executive decision-making, and its inactivation might explain why we have so little control over how our dreams go. In contrast, brain regions involved in emotional processes are cranked up, so our dreams are overly emotional compared to waking life.

Having said all that, it remains true that both waking imagination and dreaming probably use the same networks of memory associations to construct their narratives, and so dreaming might be construed simply as normal conscious imagination that has very literally gone out of control.

Q: Dr. Stickgold!
As an architect I've never put out a contract before "sleeping on it." I've solved millions of design problems while sleeping. I feel like dreaming is half the design process. I've noticed that I get anxious and crabby if I don't get enough dream time in. Have you seen this pattern in others? Cornelia Griffin, Minneapolis, Minnesota

Stickgold: I think you've summed up my research career to date, as well as my hopes for the next 10 years. Aside from the more cognitive component that you describe as problem solving, the other big issue for me is the emotional one. I often jokingly say one of my big goals in research is to figure out what it is about a 90-minute nap that can convert a psychotic dwarf into a delightful 2-year old!

Related Links

  • Sleep

    Why do we need sleep? Part of the answer may be to strengthen memories.

  • Sleep: Expert Q&A

    Matt Walker of Harvard Medical School answers questions on how sleep impacts our ability to learn.

  • The Sleep-Memory Connection

    Explore the stages of a good night's sleep and the research linking sleep to memory.

  • Sleepless Surgeons

    How important is sleep to a surgeon’s performance? Neil deGrasse Tyson visits a Harvard sleep researcher to find out.