TURKU, Finland – Where do our brains “go” when we fall asleep? A supernet in the center of the brain can help solve one of the greatest scientific mysteries – how does human consciousness work? Scientists in Finland have discovered a central central network filled with the same activity, regardless of whether the person sleeps normally or loses consciousness due to anesthesia.
Researchers at the University of Turku conducted two experiments that first revealed the natural mechanisms behind human consciousness and their connection to how people respond during sleep. One study examined the brain activity of people under medical anesthesia, while the other looked at how individuals responded while sleeping naturally and after waking up.
In addition to using brain imaging technology, the researchers also asked participants a series of questions when they woke up. These topics included whether the volunteer was aware of his surroundings or remembered one of his dreams.
“A major challenge was to design a configuration, where the brain data in different states differ only in terms of consciousness. Our study overcomes many previous confounders and, for the first time, reveals the neural mechanisms underlying connected consciousness, ”said principal investigator Harry Scheinin in a university statement.
Unconsciousness comes in many forms
Researchers say natural sleep and experimental anesthesia are powerful research tools in the study of human consciousness. In previous studies, scientists were perplexed by the waking state versus a supposed state of unconsciousness. Whether or not a person is conscious is often defined by their behavior. For example, some may assume that a person without significant responses is unconscious. However, studies show that not responding does not necessarily mean that the person is unaware of what is around them and that they are not necessarily unconscious.
A person who does not respond may still be aware of his surroundings, which means that he is still “connected”, while another person may not be aware, but still experiencing his inner world and is “disconnected”.
In the new study, scientists wanted to identify “specific state patterns” in brain activity, looking at “connected” and “disconnected” states of consciousness. They also aimed to discover the general effects of anesthesia and sleep, comparing different doses of drugs and different stages of sleep.
“This unique experimental project was the key idea of our study and allowed us to distinguish changes that were specific to the state of consciousness from the general effects of anesthesia”, explains the first study and anesthesiologist Annalotta Scheinin.
What parts of the brain make up the super network?
The researchers looked for networks in the brain linked to human consciousness. They did this by measuring the brain activity of adult men as they fell asleep and were anesthetized using a computed tomography (PET) scan. This is an imaging test that allows doctors to see how your brain is working.
The researchers woke patients in the middle of the experiment to interview them and confirm their connection status, or how aware they were of their environment. They found that changes in the connection are linked to a crucial network that connects several deep areas of the brain.
These regions include the thalamus (which shares motor and sensory signals with other parts of the brain), the cingulate cortex (formation and processing of emotions) and the angular gyres (spatial cognition, memory recovery and attention).
Rewriting common beliefs
The study found that these regions experienced less blood flow when one of the volunteers lost their connection and more blood flow when they regained consciousness. This is the case for both sleep and anesthesia, suggesting that the changes correspond more to the connection than to the effects of sleep or drugs.
“General anesthesia seems to resemble normal sleep more than traditionally thought. This interpretation, however, is in line with our recent electrophysiological findings in another study of anesthesia ”, says Harry Scheinin.
“Because of the minimal delay between waking up and the interviews, the current results significantly increase our understanding of the nature of the anesthetic state. Against a common belief, total loss of consciousness is not necessary for successful general anesthesia, as it is sufficient to just disconnect the patient’s experiences from what is happening in the operating room, ”explains Annalotta Scheinin.
The findings appear in the newspaper JNeurosci.
SWNS writer Laura Sharman contributed to this report.