Like islands sticking out of the smooth surface of the ocean, dreams pierce our sleep with incoherent episodes of consciousness. Where do these scraps of thoughts come from in the dormant brain? This question has long worried scientists and philosophers. For decades, scientists have linked dreams to the phase of rapid eye movement (BDG), when the resting brain paradoxically produces high-frequency brain waves that are very similar to those that are born during wakefulness.
And yet we see dreams not only during the BDG. Several strange studies have revealed signs of dreaming during non-BDG sleep, when the brain has a slow wave activity – opposite to an anxious, active, conscious state. And now, thanks to the research, which was published in Nature Neurosciece, we seem to have begun to grope for the answer to the tricky dilemma.
Carefully following the brain waves of sleeping volunteers, a group of scientists from the University of Wisconsin accurately identified a local “hot spot” in the brain that activates when we sleep, regardless of the phase of sleep in which the person is.
“You really can determine the signature of the sleeping brain,” says study author Dr. Francesca Siklari.
Moreover, using an algorithm developed on the basis of her observations, a group of scientists could accurately predict when a person is asleep, with 90% accuracy, and more …
… and here is the most interesting …
… approximately parse the content of dreams.
“We found out that the sleeping brain and the waking brain can be much more similar than imagined,” says Siklari.
This study not only opens the door for the simulation of dreams for PTSD therapy, but it can also help scientists to find a thread to the mystery of consciousness.
“The importance of this article is simply astounding,” says Dr. Mark Blagrov of Swansea University in Wales, who did not participate in the study.
During a full night sleep cycle, we go through different stages, characterized by distinctive pictures of the brain. Scientists often use the EEG to accurately capture each stage of sleep, which involves placing 256 electrodes on the human skull and then tracking the number and size of brain waves at different frequencies.
When we begin to doze, our brains show low-frequency activity, which runs all over the surface. These waves signal that neurons are in a “quiet state” and are not able to communicate between brain regions – therefore low frequency activity is often associated with loss of consciousness.
These slow fluctuations of non-BDG sleep ultimately become high-frequency activity, signaling the transition to the phase of rapid eye movement. This phase of sleep is often associated with bright dreams – and this connection is so deeply rooted in the study of sleep that the cases of the BDG phase without dreams or dreams in the non-BDG phase were often ignored as oddities.
It turns out that these strange cases hinted to us that our current understanding of the neurobiology of sleep is not complete.
To reconsider these paradoxical results, Siklari and her team monitored the brain activity of 32 volunteers using EEG and woke them up during the night at random intervals. Then the scientists asked the sleepy participants if they had dreamed something, and if so, what it was. In total, this happened 200 times a night.
But instead of seeing the global shift in activity associated with sleep, scientists were surprised to find a region of the brain in the back of the head that dynamically shifted its activity based on emerging dreams.
Dreams were associated with a decrease in low-frequency waves in the “hot zone” and with the increase of high-frequency waves reflecting high rates of neuronal activation and brain activity. This was a kind of awakening, independent of the stage of sleep or the general activity of the brain.
“Everything indicates that a very limited, clearly defined activation of the brain is needed to generate a conscious experience,” says Siklari. “Until now, we thought that large areas of the brain should be activated to generate conscious experience.”
The fact that the hot zone connects to the action during sleep, has a certain meaning. Previous work has shown that stimulating these brain regions with an electrode can cause a feeling of being “in a parallel world”. This hot zone also contains sites that integrate sensory information to build a virtual world model around us. This kind of modeling lays the foundation for many of our imaginary worlds, and this hot zone is perfectly adapted for this business, “the authors say.
If the active hot zone is in fact a “sleep signature”, its activity should be able to tell if the person is sleeping at a particular time. The authors created the algorithm based on their results and checked its accuracy on a separate group of people.
“We woke them up whenever the algorithm told us they were asleep, only 84 times,” the researchers write.
In total, this algorithm showed a 90 percent accuracy in the analysis of the presence of sleep-even in cases where the participants in the experiment did not remember the contents of their dreams, but were sure they were asleep.
Since the hot zone contains sites that process visual information, scientists have wondered whether it is possible to access the contents of the dreams of subjects using EEG readings.
Dreams can be exceptionally tangible, with unfolding events, or completely abstract, as a free fantasy, scientists say. Persons, places, movements and speech are all habitual components of dreams that are processed by easily identifiable regions of the hot zone, so the researchers decided to focus on these aspects.
What is noteworthy, volunteers who told what they said in their dreams, showed activity in the brain areas responsible for speech; And those who dreamed of people showed activity in the centers of face recognition.
“This suggests that dreams use all the same areas of the brain as the conscious experience during wakefulness for a certain content,” says Siklari, noting that earlier studies could only show this by the example of the “twilight zone”, the transition between sleep And wakefulness.
Finally, scientists are interested in what happens when we sleep, but do not remember the specific details. It turned out that this strange state has a separate EEG signature: remembering the details of sleep was associated with a burst of high-frequency activity in the fore parts of the brain.
Interesting questions are born, for example, whether the frontal lobes of the brain respond to lucid dreams, a special state, when people understand that they are asleep and can change the contents of sleep.
Awakening of life
Scientists can not yet explain what activates the hot zone during sleep, but the answers can tell us whether sleep has a biological purpose, for example, recycling memories into big concepts about the world.
Mapping the activity of the sleeping brain can also lead to the emergence of ways to directly manipulate our dreams, using non-invasive procedures, for example, transcranial stimulation by current. Introduction to sleep can help people with insomnia, and the destruction of anxious sleep can help patients with PTSD get better sleep.
Dr. Julo Tononi, the lead author of the study, believes that the consequences of this study go well beyond sleep.
“We were able to compare how the sleeping brain behaves compared to the waking state. This research can become a valuable model for the study of consciousness, “he says.