For centuries, the role of dreaming has been a compelling mystery that has stumped scientists. Why do we dream? What is going on in our brains when we dream? Recent research has revealed significant new insights and points toward an entirely new understanding of the complex neurological processes involved in dreaming, ultimately revealing the activity of our brain while dreaming to be similar to that seen in waking states.
The new study from scientists at the Wisconsin Institute of Sleep and Consciousness offers us several novel insights into what's happening inside our brains while we dream. The study countered preexisting ideas about the connection between Rapid Eye Movement (REM) sleep and dreaming, finding that dreams can equally occur during both REM and non-REM sleep.
The study also found that while the activity of dreaming causes several parts of the brain to spark, there is always a "hot zone" of high frequency electrical activity occurring in posterior cortical regions of the brain when dreaming is taking place. The activity in this region was considered by researchers as correlating with conscious experiences in sleep.
As well as revealing what parts of the brain were active while dreaming, the study examined how the content of a dream was reflected in different parts of the brain. The subjects in the experiment were fitted with 256 electrodes creating a high-density electroencephalographic report of their brains. They were awakened several times with a tone and asked to report on the content of their dreams.
A compelling part of the study identified that the same parts of the brain in charge of certain actions when awake, such as identifying speech or faces, became active when dreams contained those specific elements. For example, it was observed that dreams containing speech triggered activity in the left side of the cerebral cortex, the language perception and understanding area of the brain.
"This suggests that dreams recruit the same brain regions as experiences in wakefulness for specific contents," says Dr Francesca Siclari, one of the lead authors on the study. "This also indicates that dreams are experiences that truly occur during wakefulness, and that they are not 'inventions' or 'confabulations' that we make up while we wake up."
The study also tested whether observational EEG data could be used to predict whether a subject was dreaming. They researchers successfully predicted the absence of dreaming 81 percent of the time, and the presence of dreaming in a subject 92 percent of the time.
"This is the first time someone has shown that absent or forgotten dream experiences also carry a distinct EEG signature, which should encourage us to take reports of dream experiences at face value," Dr Siclari says.
The study not only sheds light onto the neurological processes behind dreaming, but also offers valuable insight into the nature of consciousness.
"In this way we could zoom in on the brain regions that truly matter for consciousness and avoid confounding factors having to do with being awake rather than asleep or anesthetized," explained senior author Professor Giulio Tononi.
By illustrating how dreams ignite similar parts of our brains that engage with reality in waking states, the researchers are keen to define dreams as a form of consciousness that occurs during sleep.
The team's study was recently published in the journal Nature Neuroscience.
Source: University of Wisconsin-Madison