The Thalamus

Bernie Baars and Jim Newman have developed a concept which for Baars is expressed in psychological terms as the Global Workspace or the working memory, and for Newman is expressed physiologically in their proposed neural corrrelate of working memory the extended reticulo-thalamic activating system (eRTAS) with its massive interconnections to and from the cortex.
Baars and Newman talk about the "Global Workspace"

for extracts from the video:
Baars on the Theatre metaphor for working memory; and
Newman on the eRTAS.

I think that for me this was the most significant idea of the conference: this demonstration of the psychological: the working memory; being very closely coupled with the physiological: the eRTAS; as a really functional solution to the NCC problem. It is the extraordinary amount of interconnectivity between the thalamus and the cortex that allows the cortex, particularly the forebrain, to regulate the flow of information to itself: so that it doesn't get swamped, so that it can focus on what it needs to know about from moment to moment. This is a huge, self-regulatory feedback circuit which binds the processes of the brain, or at least those important to consciousness, together over time, within the time scale of our normal moment-to-moment operating frame.

[See the e-seminars led by James Newman for a series of papers and commentaries on the "Thalamo-cortical Foundations of Conscious Experience"]

Now to return to Joseph Bogen. Bogen is on a search for the neural basis of "subjectivity". He suggests that any candidate for a neural correlate of consciousness must have widespread ditributivity, i.e. inward and outward connectivity. He refers to a subsection of the thalamus: the intralaminar nuclei as a site which satisfies his criteria as a primary site for subjectivity and he gives as primary evidence for this the fact that although quite widespread lesions in most parts of the brain do not cause loss of consciousness, merely modification of it, a very small lesion in the intralaminar nuclei will cause irrreversible loss of consciousness.

Rodolfo Llinas provided some detail on the physical shape of the interconnections through the thalamus as mentioned by Jim Newman. He argues that "the form and the way things are connected in space are very important" [Llinas' presentation to Tucson II] and makes the wonderful statement that:

Llinas suggests that the view of the brain as a whole may give us an indication of how the brain works as a whole. He (as do Baars and Newman) describes the brain as being like the hub of a wheel. There is an array of radial projections carrying information patterns from all the afferent sensory systems upto the thalamus and projecting all the sensory pathways on up into the cortex. There are also a massive array of neural projections back from the cortex onto the thalamus. These project onto the array of gatelets of the intralaminar nuclei (see Bogen) and give the cortex control over what information it is getting.

Llinas has been using magneto-encephalography, (a vastly more sensitive brain activity sensing technology than electro-encephalography) to watch the brain functioning and has discovered bursts of 40Hz oscillation. These bursts are re-set when a sensory event occurs in an experimental situation and travel deep into the brain in a dialogue with the cortex. These continue while you are asleep. It is probable that dreams are the free-running of these oscillations through the thalamo-cortical system triggered only by the inherent noise of a biological system temporarily lacking the external sensory stimulus of being awake.