Sleep is a complex business. While dreaming, your brain is as active as when you are awake, and the varieties of sleep experience are broad and wondrous. And sleep matters to us. We worry about getting too little, fret about not being able to do it and suffer when it goes wrong. Yet sleep research lags way behind other areas of neuroscience.
One reason for this is that sleeping subjects can't report their experiences. Even dreams, however dramatic, tend to drift from memory like wisps of smoke. It is also very difficult to look inside a sleeper's brain. Functional imaging machines clatter and clang and "helmet"-type imagers defeat any attempt to put your head on a pillow. The only practical way to measure brain activity in sleep is by using EEG, which charts the differing waves of neural oscillation in each part of the brain as it shifts from state to state. EEG involves sticking multiple electrodes on the scalp and is hardly conducive to sleeping like a baby . Many studies, though, demonstrate that it is not entirely sleep-defeating either.
Photograph courtesy of Columbia University in New York
Researchers at the Creative Center in Industrial Technology Research Institute in Taiwan have used EEG to compare two sleep states: "ordinary" dreaming and lucid dreaming. They used a new method of analysis called Multiple Scale Entropy (MSE) which "scores" the level of complexity of the brain signals. A high score suggests that many different brain regions are active and interconnecting, while a low score suggests that parts of the brain are effectively "turned off" or disengaged from one another.
Dreams are often bizarre, but in normal dreaming everything seems perfectly natural. Your mother turns into a chicken and sings "The Red Flag"? Sure. You grow eight arms and sit on a cloud.? Cool. Your critical faculties are effectively turned off, along with your normal sense of self.
Lucid dreams differ in that they are accompanied by normal waking alertness, including self-awareness, reflection, intentionality, motivation and memory. When a dream turns lucid, it feels exactly like waking up, except that instead of waking in your bed you wake into whatever scene was being enacted in the dream. The usual trigger is a thought along the lines of, "This is just crazy -- I can't really be tobogganing down the side of the Empire State Building -- it must be a dream!" The thought seems to break the spell of the dream, releasing you into full consciousness, yet the hallucination continues as vividly as before. You can either allow the dream to meander on while you enjoy the ride, or you can direct it, merely by thinking of what you would like to happen next. If you fancy a stroll on a tropical beach, you can decide that when you turn around the scene will be transformed into an island paradise, or if you fancy having a chat with a friend you can simply decide that they will walk out of a nearby building and greet you
The difference in cognition between the two types of dreaming suggests that lucid dreaming occurs when the frontal parts of the sleeper's brain -- which are normally "off-line" during REM sleep -- click back in, bringing back self-consciousness. However, the back parts, which process sensations, are not synced up with the wide awake frontal cortex. So instead of taking in information from the outside world, they remain closed off in the word of the dream, creating a virtual world as convincing as the one outside.
The MSE analysis carried out by the Taiwan researchers showed that the complexity score of a lucidly dreaming brain was significantly higher than that of the same brain during ordinary dreaming. It confirms the theory that brain areas are cut off from one another in ordinary dreams, which is probably why the sensory areas can throw up bizarre hallucinations without exciting skepticism from the critical and self-aware part.
To date, very few people lucid dream regularly, and even fewer can control the dreams once they occur. Those that can, however, have a glorious playground: Without benefit of computers, online gaming or brain interfaces, they can turn on and lose themselves in a perfect virtual reality. It is a pity that it is so difficult to be done at current stage.