What happens to my brain when I lose consciousness during general anesthesia and normal sleep? Finnish scientists have studied this question with new design of experiments and functional brain imaging. They succeeded in isolating certain changes related to consciousness from a wider range of overall effects and found that the effects of anesthesia and sleep on brain activity were surprisingly similar. These new discoveries point to a common central core brain network that underlies human consciousness.
Explaining the biological basis of human consciousness is one of the greatest challenges of science. Loss and recovery of consciousness regulated by drugs or physiological sleep has been adopted as a model system in the study of human consciousness, but previous findings have been confused by many experimental simplifications.
“One major challenge was to design different setups for brain data in different states only with respect to consciousness. Our research overcomes many previous confusions and, for the first time, underlies connected consciousness. “We have revealed a neural mechanism,” says Harry, a principal investigator of research from Sheinin, Pharmacology Docent, anesthesiologist, and the University of Turku, Finland.
New and innovative experimental equipment
Brain activity was measured by positron emission tomography (PET) imaging during different states of consciousness in two separate experiments in the same group of healthy subjects. Measurements were taken during awakening, while the levels of the two anesthetics were elevated and at constant levels, and during sleep deprived awakening and non-REM sleep (NREM) sleep.
In the first experiment, subjects were randomly assigned to receive propofol or dexmedetomidine (two anesthetics with different molecular mechanisms of action) in stages until the subject became unresponsive. In sleep studies, they were allowed to fall asleep naturally. In both experiments, subjects were excited to achieve a rapid recovery to the reaction state, followed by an immediate and detailed interview of the subjective experience from the previous period of non-responsiveness. At the NREM sleep stage, which was verified as unresponsive anesthesia, subsequent reports of psychological content did not include cognitive signs of the surrounding world, indicating that study participants were disconnected. I did. Importantly, drug administration in the first experiment was not changed before or during changes in the subject’s behavioral state.
“This unique design of experiments was an important idea in our study and made it possible to distinguish changes specific to the state of consciousness from the overall effect of anesthesia,” said the anesthesiologist, PhD. Candidate and first author of the treatise, Analotta Shinin, explains.
Researchers have discovered a common central core brain network
Comparing responsive and connected brain PET images with non-responsive and amputated brain PET images, scientists found that thalamus, cerebral cortex, and angular gyrus activity used anesthetics, drug concentrations, And found that they are affected regardless of the direction of change in state. Consciousness. When comparing physiological sleep to sleep-deprived arousal, surprisingly similar findings were obtained. When the amputated state was compared to the fully awake state, the changes in brain activity were much more extensive. Therefore, state-specific findings were separable, unlike the overall effects of drug-induced anesthesia and natural sleep, including extensive suppression of brain activity throughout the cortical area.
These findings identify the core brain network that is the basis of human consciousness.
“General anesthesia seems to be more like normal sleep than previously thought, but this interpretation is in good agreement with recent electrophysiological findings in another anesthesia study,” Harry Sheinin said. say.
Subjective experience is common during general anesthesia
Interestingly, unresponsiveness rarely shows unconsciousness (that is, no subjective experience), as most participants reported internally generated experiences such as dreams in interviews. This is not a completely new discovery, as dreams are commonly reported by patients after general anesthesia.
“But because the delay between awakening and interview is minimal, the current results add significantly to the understanding of the nature of the anesthesia state. Contrary to common belief, for successful general anesthesia. You don’t have to be completely unconscious, enough to separate the patient’s experience from what’s happening in the operating room, “explains Annalotta Scheinin.
New research sheds light on the basic properties of human consciousness and provides new information on brain function in the intermediate state between arousal and complete unconsciousness. These findings may also challenge our current understanding of the nature of general anesthesia.
The experiment was conducted at the Turku PET Center in collaboration with Harry Sheinin’s research group, which studies the mechanism of anesthesia, and Professor Anti Lebonsoo, a psychology professor who studies human consciousness and the brain from the perspective of philosophy and psychology. I did. Michael Alkire of the University of California, Irvine. The Turku PET Center is the Finnish National Institute founded by the University of Turku, the University of Ovo Academia and the University of Turku Hospital. This study was funded by the Academy of Finland and the Jane and Atos Elco Foundation.