Memory and dream are the same

The night side of consciousness

Copyright: breadandbutterfly / / Meike Ufer

I dream, therefore I am - or not? What kind of self is that dreaming? What's happening in the brain? Neuroscience is making headway in answering these questions, but a little philosophy can't hurt either.

Scientific supervision: Prof. Dr. Bjorn Rasch

Published: 08/27/2013

Level: medium

  • Consciousness is not a matter of all or nothing. During the night we go through several levels of consciousness.
  • The connection between the individual regions in our brain changes in a significant way.
  • In dreams we are, like in waking, “naive realists”: We experience a world that we take for reality.
  • The sleeper is only aware that he is dreaming in lucid dreams.
  • Whether we dream all night or whether there are breaks in between is still controversial.
  • An elegant experiment with lucid dreamers has shown that our sense of time in dreams resembles that of our waking consciousness.

Michael Czisch from the Max Planck Institute for Psychiatry in Munich not only examined lucid dreams using magnetic resonance imaging, but also carried out sophisticated time series analyzes of the fMRI signals from sleepers together with his colleague Victor Spoormaker. The researchers were able to see how the activity of the entire brain varies during different phases of sleep and while waking.

The following picture emerges: In the waking state, the centers of the human brain are linked to one another in such a way that the signals are optimally transmitted in individual regions, i.e. in a narrow space, but at the same time longer distances can be covered in rapid steps. Technicians speak of a small world network. It is also characteristic of social networks, such as Facebook acquaintances.

When falling asleep, i.e. when sleeping lightly, global networking increases, but the connections take on a more random, chaotic character. In contrast, in deep sleep, the researchers observe increased local clustering, as if the individual regions were busy with themselves. This fits in with the deep sleep task of consolidating memories. When archiving, one does not like to be disturbed by external impressions. However, long-distance loss of communication results in the brain's ability to pool information being greatly reduced - a state of unconsciousness similar to that experienced under anesthesia.

In certain phases of REM sleep, the connection between thalamus and cortex is strengthened again - this could explain that rudimentary consciousness arises in dream sleep.

I can't stop the locomotive. The brakes fail. The machine jumps off the rails and instead continues on the curb in front of the train station. There, an obstacle! Looks like a big dumpster. I head for that. And now, finally, the locomotive is standing. I get off and steal away as quickly as possible - meandering through a crowd of passers-by who saw the collision. Nobody stops me.

A dream. One that makes me think when I wake up. What did i just do? Hit and run, albeit on foot. I would never do something like that in real life! Especially not after an accident with such a conspicuous vehicle. How do I get this locomotive at all? I don't even like to drive. In the dream event, however, my vehicle didn't seem implausible to me at all. There was a history. But now I can only vaguely remember them after waking up.

You could almost say that my dream- me and my day- me are two different people. But they are not that different - they share the same brain. The same brain in two different states of consciousness.

Consciousness is not a matter of all or nothing

Jennifer Michelle Windt sees it that way too. The philosopher dealt with dream consciousness in her doctoral thesis with Thomas Metzinger in Mainz. Unlike her American predecessor Norman Malcolm, who in the 1950s still categorically claimed that anyone who was asleep could not be conscious for logical reasons, says Jennifer Windt, that is very possible. Consciousness is not a matter of all or nothing.

After all, we experience something in a dream, we are in a world that we can experience: there is a train station in a small town, there is a locomotive, a garbage container, and there are people on the street. We experience this world very subjectively as our here and now, argues Windt. Even if it is just a construction of our brain.

However: Isn't the world that we experience in wakefulness also a construction of our brain? On the Ge hirn .info one can read dozens of times that, for example, seeing is a complicated process that only creates a visual impression from physical signals (light waves that hit the retina) in many neuronal steps. (Seeing) “What we experience is never the real world,” says the philosopher. “We always generate a model.” Nonetheless, we believe in the reality of our models, we go through the world as “naïve realists” - while awake and in dreams.

An exception are people who dream lucidly. These enviable contemporaries become aware while dreaming that they are dreaming. Some then even control their dream in a targeted manner, for example, they can fly or walk through walls, have sex with Brad Pitt or the horror figures of their nightmares intimidate them so convincingly that they run away.

Lucid dreamers advance brain research

Such skills are not so rare: In a representative survey that dream researcher Michael Schredl carried out in Germany in 2010, it came out that 51 percent of those surveyed knew lucid dreams from their own experience. One in five even dreams clearly once a month. And so, lucid dreamers have recently been explored more and more closely. They are considered by psychologists, sleep and brain researchers, but also philosophers like Jennifer Windt as guides to the fundamentals of our consciousness.

Unfortunately, I am not one of those elite sleepers - I am defenselessly exposed to my dreams. And often these boring dreams plague me, in which I make entries on websites again and again and in the process I am threatened with forgetting something important - it is as if my work life continued seamlessly in my sleep. Do I actually dream all night? Are there no breaks?

For a long time, sleep researchers assumed that humans only dream in REM sleep. These are the phases of sleep that are characterized by rapid eye movements (REM) and by conspicuous signals in the EEG. (Anatomy of sleep) During these sleep phases only the eyes - and the respiratory muscles function, the rest of the voluntary muscles are completely paralyzed.

Aggressive dreamers and eating sleepwalkers

It's better that way, otherwise we might act out our dreams, run through the apartment in pajamas and beat up our bed neighbor because we think he's a pursuer. With a certain disease - REM sleep behavior disorder - that is exactly what happens in real life. This is not funny for those affected and their relatives, especially since the disease, which is also known as Schenck's syndrome, can be a sign of the onset of Parkinson's disease. (When every night turns into a nightmare)

It is known that these patients can often remember the contents of their nightmares for a long time - mostly they are being persecuted by some evil forces. But they do not remember their own, very real aggressions - a special form of distortion of consciousness. Sleepwalkers, on the other hand, as we now know, begin their nocturnal wanderings from non-REM sleep. With them, the body becomes, so to speak, independent, while the consciousness continues to sleep. Their behavior does not necessarily have anything to do with the content of dreams, and most of the time they do not even remember their nocturnal excursions, although some of them even eat meals.

Scientists now assume, however, that we all also dream in non-REM sleep, in what is known as deep sleep. Corrado Cavallero from the University of Bologna specifically awakened test subjects in the sleep laboratory during these phases - and two thirds of them remembered recent dream experiences. "Today most sleep researchers assume that we are actually dreaming all the time," says the science journalist Peter Spork in his "Sleep Book", "that we can only remember our dreams to varying degrees when we are awakened from different stages of sleep." he would confirm my worst nightmare - that my nocturnal experience knows no break. Jennifer Windt, on the other hand, believes it is credible when people say after waking up that they have just not dreamed anything.

The sense of time in the dream

It's hard to prove both. And there are also completely different views. The well-known psychologist Jan Born, to whom we owe a lot of knowledge about learning in sleep (learning in sleep), is convinced, for example, that our dreams are not at all remembered nocturnal experiences, but pure constructs: stories that the brain wakes up from the Concocting nerve signals from the last restless minutes of sleep.

Daniel Erlacher considers this theory to be an "old fairy tale" that experimental research has now done away with. The sports scientist from Heidelberg University is one of the pioneers of lucid dream research in Germany. He has written a “guide to lucid dreaming” and maintains the website www .klar traum .de. Erlacher has made experiments with people who are not only capable of lucid dreaming, but can also signal to the experimenter in the sleep laboratory by rolling their eyes that a lucid dream is about to begin. Before going to bed he asked some of them to count from one to ten in a lucid dream and then give an eye signal again. Erlacher found that as much time passed as if you were counting while you were awake. They also needed the usual amount of time in their sleep for certain gymnastics exercises that the lucid dreamers dutifully completed for the researcher. “In a dream, time passes no differently than when you are awake,” Erlacher concludes. His results do not fit the idea of ​​a scene made up after you wake up.

Michael Czisch from the Max Planck Institute for Psychiatry in Munich even put lucid dreamers in the fMRI scanner - two fascinating interviews on www .das ge hirn .info tell about it. (Waking dreams with Michael Czisch and consciousness with Michael Czisch) According to his research, it looks as if the "awakening" of a meta-consciousness - exactly when the sleeper begins to become aware of his situation as a sleeper - can also be grasped from a physiological perspective: The activity in a whole network of brain regions increases. These include areas that earlier researchers have already associated with self-reflection: the dorsolateral prefrontal cortex on the forehead (especially the right one) and the precuneus on the occiput.

I want to try to remember when a locomotive derails again.

for further reading:

  • Erlanger, Daniel: "Attention out there, I'm dreaming!", Psychology Today. 2013 June; P. 69 (to the text).
  • Noreika, V et al: New perspectives for the study of lucid dreaming: From brain stimulation to philosophical theories of self-consciousness. International Journal of Dream Research 2010; 3 (1): 36 - 45 (to the text).
  • Rauch, Judith: The power of dreamless sleep, image of science. 2012; 12: 32 (to the text).
  • Spoormaker VI, Czisch M: Functional Connectivity in Sleep. Network analyzes of combined EEG- fMRI measurements. Somnology - Sleep Research and Sleep Medicine 2012; 16 (1): 43 - 52 (to the abstract).
  • Spork, Peter: The Sleep Book. Why we sleep and how we can best manage it, Hamburg 2012.
  • Voss U et al: Measuring consciousness in dreams: The lucidity and consciousness in dreams scale. Consciousness and Cognition 2013 Mar; 22 (1): 8 - 21 (to the abstract).
  • Windt JM, Metzinger: The Philosophy of Dreaming and Self- Consciousness: What Happens to the Experiential Subject during the Dream State? In: Barrett Deirdre, McNamara Patrick: The New Science of Dreaming. Westport, Connecticut 2007, pp.193-247 (to the text).