correlates of return of consciousness

I dealt with this paper, citation below, when it came out last May. But now Deric Bownds Blog (here) links to it. I am revisiting the paper, not in full – for that see the previous post (other post).


Three aspects seem very important: the difference between the state of consciousness and the contents of consciousness; how little activity of the neocortex is needed for the state of consciousness as opposed to the contents; and, the importance of the thalamus to consciousness.


Whereas theories on the particular contents of consciousness, such as visual consciousness, argue for the importance of cortical structures, theories focusing on consciousness as a state stress the importance of subcortical or thalamocortical structures . Having awareness of the environment or of one’s self is fundamentally based on being in a con scious state. There is limited human data on which brain structures engage to serve this foundation of consciousness. This study was designed to reveal the minimal neural correlates associated with a conscious state. …

The recovery from anesthesia does not occur all at once, but rather it appears to occur in a bottom-up manner. When emerging from deep anesthesia there will first be signs of autonomic arousal, followed by a slow return of brainstem reflexes, eventually leading to reflexive or uncoordinated somatic movements that occur somewhat before subjects can willfully respond to simple commands. As shown in our results, only minimal cortical activity is necessary at this point. Thus, emergence of a conscious state, the essential foundation of consciousness, precedes the full recovery of neocortical processing required for rich conscious experiences. We propose that the failure of simple processed EEG monitoring technology to detect patient awareness during anesthesia is at least partly due to the aforementioned pattern of brain arousal. …

The structures that activated when consciousness resumed were the brainstem, the thalamus, the hypothalamus, and the ACC (anterior cingulate cortex).

Langsjo, J., Alkire, M., Kaskinoro, K., Hayama, H., Maksimow, A., Kaisti, K., Aalto, S., Aantaa, R., Jaaskelainen, S., Revonsuo, A., & Scheinin, H. (2012). Returning from Oblivion: Imaging the Neural Core of Consciousness Journal of Neuroscience, 32 (14), 4935-4943 DOI: 10.1523/JNEUROSCI.4962-11.2012

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