New Study Images the Brain as It Loses Consciousness
                     New Study Images the Brain as It 
Loses Consciousness
What happens in the brain when our conscious awareness fades during general 
anesthesia and normal sleep? News from pharma industry says that Finnish 
scientists studied this question with novel experimental designs and functional 
brain imaging. They succeeded in separating the specific changes related to 
consciousness from the more widespread overall effects, and discovered that the 
effects of anesthesia and sleep on brain activity were surprisingly similar. These 
novel findings point to a common central core brain network fundamental for 
human consciousness.
News from pharma industry says that it explaining the biological basis of human 
consciousness is one of the greatest challenges of science. While the loss and 
return of consciousness, as regulated by drugs or physiological sleep, have been 
employed as model systems in the study of human consciousness, previous 
research results have been confounded by many experimental simplifications.
According to pharmaceutical updates "One major challenge has been to design a 
set-up, where brain data in different states differ only in respect to consciousness.
Our study overcomes many previous confounders, and for the first time, reveals 
the neural mechanisms underlying connected consciousness," says Harry 
Scheinin, Docent of Pharmacology, Anesthesiologist, and the Principal Investigator
of the study from the University of Turku, Finland.
 
A new and innovative experimental set-up
News from pharma industry says brain activity was measured with positron 
emission tomography (PET) imaging during different states of consciousness in 
two separate experiments in the same group of healthy subjects. According to 
pharmaceutical updates measurements were made during wakefulness, 
escalating and constant levels of two anesthetic agents, and during sleep-
deprived wakefulness and Non-Rapid Eye Movement (NREM) sleep.
In the first experiment, the subjects were randomly allocated to receive either 
propofol or dexmedetomidine (two anesthetic agents with different molecular 
mechanisms of action) at stepwise increments until the subjects no longer 
responded. In the sleep study, they were allowed to fall asleep naturally. 
According to pharmaceutical updates in both experiments, the subjects were 
roused to achieve rapid recovery to a responsive state, followed by immediate 
and detailed interviews of subjective experiences from the preceding 
unresponsive period. Unresponsive anesthetic states and verified NREM sleep 
stages, where a subsequent report of mental content included no signs of 
awareness of the surrounding world, indicated a disconnected state in the study 
participants. Importantly, the drug dosing in the first experiment was not changed
before or during the shift in the behavioral state of the subjects.
According to pharmaceutical updates -"This unique experimental design was the 
key idea of our study and enabled us to distinguish the changes that were specific 
to the state of consciousness from the overall effects of anesthesia," explains 
Annalotta Scheinin, Anesthesiologist, Doctoral Candidate and the first author of 
the paper.
 
Pharmaceutical companies in the news- Researchers discovered a common 
central core brain network
When PET images of responsive and connected brains were compared with those 
of unresponsive and disconnected, the scientists found that activity of the 
thalamus, cingulate cortices and angular gyri were affected independently of the 
used anesthetic agent, drug concentration and direction of change in the state of 
consciousness (see figure). Strikingly analogous findings were obtained when 
physiological sleep was compared with sleep-deprived wakefulness. Brain activity 
changes were much more extensive when the disconnected states were 
compared with a fully awake state. pharmaceutical companies in the news says 
that state-specific findings were thus distinct and separable from the overall 
effects of drug-induced anesthesia and natural sleep, which included widespread 
suppression of brain activity across cortical areas.
Differences in brain activity between connected and disconnected states of 
consciousness studied with positron emission tomography (PET) imaging. Activity 
of the thalamus, anterior (ACC) and posterior cingulate cortices (PCC), and 
bilateral angular gyri (AG) show the most consistent associa-tions with the state 
of consciousness (A = general anesthesia, B = sleep). The same brain struc-tures, 
which are deactivated when the state of consciousness changes to disconnected in
general anesthesia or natural sleep (cool colors in the left columns), are 
reactivated when regaining a con-nected state upon emergence from anesthesia 
(warm colors in the right columns). Credit: University of Turku
These findings According to pharmaceutical companies in the news  
identify a central core brain network that is fundamental for human 
consciousness.
"General anesthesia seems to resemble normal sleep more than has traditionally 
been thought. This interpretation is, however, well in line with our recent 
electrophysiological findings in another anesthesia study," says Harry Scheinin.
 
Subjective experiences are common during general anesthesia
Interestingly, unresponsiveness rarely denoted unconsciousness (i.e., total 
absence of subjective experiences), as most participants reported internally 
generated experiences, such as dreams, in the interviews. This is not an entirely 
new finding as dreams are commonly reported by patients after general 
anesthesia.
"However, because of the minimal delay between the awakenings and the 
interviews, the current results add significantly to our understanding of the 
nature of the anesthetic state. Against a common belief, full loss of consciousness 
is not needed for successful general anesthesia, as it is sufficient to just 
disconnect the patient's experiences from what is going on in the operating 
room," explains Annalotta Scheinin.
According to pharmaceutical companies in the news sheds light on the 
fundamental nature of human consciousness and brings new information on brain
functions in intermediate states between wakefulness and complete 
unconsciousness. These findings may also challenge our current understanding of 
the essence of general anesthesia.