For some time now there has been controversy between the people who think that the cerebral cortex is important to consciousness and those that think it is sited in the brain stem. In this question I note that the arrangement of connection between the precuneus and the PAG would offer a compromise allowing PAG based influence to directly affect cortex influence. In which case both schools of thought are vindicated.
I don't know whether there is any hard evidence to support this assumption, but from a structural and functional imaging point of view in pain disorders both areas seem to be involved as they are described in some papers as being altered in painful disorders. The PAG was even considered to be a migraine generator and/or antinociceptive brainstem relay (depends on what you read). It remains speculative whether both areas are connected or not, but they seem to react to similar (in this case painful) stimuli. However, this is not reported in every study and therefore might not be very consistent.
A.D. CRAIG described a specific bypass of the PAG and other stuctures of the brainstem in humans. But this bypass from the Lamina I to the thalamus, then the insula doesn't exclude the PAG and other braintem systems. So I agree with Mark : both are involved in humans. But I would add (from the views of Stephen PORGES) that it may be a hierachical functionning : the Insula (with the Anterior Cingulate Cortex and other cortical areas), may be used first for Body Awareness, and the "ancient" circuitery may be used when the first fails... Just my thoughts...
The bypass of the PAG suggests a third location that is the recipient of both the PAG, and cortex inputs. Does anybody know what this location is?
Consciousness must be based in cognition. The site http://www.cognitivestyles.com has a review of relevant direct quotes from about 300 recent papers (‘1a Lateral Frontopolar’ to ‘1f. Aspects of Depression’ on the drop-down list) which together suggest that cognition is based solely in the lateral frontopolar, medial frontopolar, anterior cingulate extending into dorsolateral prefrontal working memory, superior parietal and inferior frontal gyrus. Nothing more. You can look through the quotes and see what you think.
There is also an extended pictorial model of consciousness extracted from psychology and philosophy (eg Heidegger’s ‘Being and Time’ with both its spatiality and temporality in diagrams). Evidence from history identifies the nodes in the model with the cognitive modules in the cortex.
The model predicts that consciousness (in contrast to cognition which can be unihemispheric) always involves communication across the hemispheres, between the nodes. This communication is probably occurring somewhere down lower. This must extend far beyond something merely between the precuneus and the PAG - I too would like to know where this location is.
Both schools thus appear to be correct.
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