Finnish researchers studying the brain's consciousness discovered that brain activity while sleeping is nearly identical to brain activity while under the effects of general anesthesia. The interesting part about this discovery is that it points to there being a core brain network that holds human consciousness or at least processes the activity of it.
Human consciousness is one of the few things that sets us as a species apart from the rest of the animal kingdom – and explaining it is a little challenging. For ages, humans have used the loss of consciousness as a method for medical operations, whether through anesthesia or through blunt force.
As noted by the researchers, one of the hardest things about examining consciousness is actually setting up an experiment where the only variable is consciousness itself. If this isn't achieved than the results of any study can be flawed as there would be other factors influencing the brain.
For the study, the researchers examined patients' brains utilizing positron emission tomography, or PET. This type of imaging was taken in two different experiments and made during wakefulness, sleep, and two different types of anesthetic.
The anesthetics used were propofol or dexmedetomidine, which were administered in periodic increments until the patients stopped responding. As for the sleep, the patients were allowed to fall asleep naturally.
Following periods of unconsciousness, the patients were subjected to interviews to record all of the findings.
What this research found was that brain activity in many regions of the brain was similar independent of how the patient became unconscious. The PET imaging found activity in the thalamus, cingulate cortices and angular gyri throughout the tests.
Having analogous activity in these parts of the brain drew the researchers to the conclusion that they make up some form of central core brain network fundamental to consciousness.
One thing this study does make clear is that full loss of consciousness isn't needed for anesthesia, rather the consciousness just needs to be removed from the patient's physicality, like what occurs in sleep.
The study is published in JNeurosci, here.