#17 — Global Workspace Theory: Widespread Integration & Broadcasting of Conscious Signals - Part 2
Episode 17 of the Podcast On Consciousness with Bernard Baars explores the links between cutting edge brain evidence and how that supports or updates our understanding of consciousness and the Global Workspace Theory (GWT).
Talking Points
0:00 – Intro
5:24 – History of Global Workspace Theory
8:23 – Discussion Paper #1: Baars et al. (2013) Global Workspace Dynamics
9:32 - What is meant by “Widespread Integration?”
17:22 – The Neuroscience of Widespread Integration
25:26 – Corticothalamic Loops in Relation to GWT
30:10 – Localist vs Local-Global Theories
35:46 – “The Question of Introspection”
43:01 – How is Consciousness Assessed?
49:58 – Feelings of Knowing (FOKs)
54:33 – Discussion Paper #2: Gaillard et al. (2009) Converging Intracranial Markers...
1:04:20 – Discussion Paper #3: Herman et al. (2019) A Switch & Wave of Neuronal Activity
1:14:55 – Brain Oscillations: Gamma and Beta Bands
1:20:56 – Paper #4: Deco et al. 2019 Revisiting the Global Workspace
1:26:29 – Functional Rich Clubs
1:41:50 – The Future Quest for Consciousness
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Summary
After some quick introductions, Alea briefly summarizes their discussion in Part I on the history of Global Workspace, how the theory evolved, as well as some of the core hypotheses it generates. Now we dive into the brain evidence.
Global Workspace Theory (or GWT) was first formulated in the ‘80s as a psychological theory of how consciousness might operate. In Part I, we talked about the spotlight metaphor. One of the key predictions of GWT is “widespread integration and broadcasting.” This seems to be one of the predictions that can be most directly tested by brain activity, our topic today.
The trio delves into the first of 4 papers, namely Baars’ 2013 paper called “Global Workspace Dynamics.” This paper comes as the result of four decades of cumulative work, which pulls together the evidence as of 2013. One of its key points connecting GWT to neuroscientific evidence is that GWT does not require (or suggest) an “anatomical hub” of coordinated activity, but, instead, a momentary, dynamic “functional hub.”
Bernie explains how the conscious brain is characterized by ‘widespread integration and broadcasting.’ The cortex is like a large city with specialized neighborhoods, streets and alleys. There is an ever changing flow of traffic between them. He then suggests that the thalamus is more than a relay station of the brain, and that the sensory thalamus is an entryway to the giant cortico-thalamic (CT) system, which integrates and broadcasts conscious information.
Next, Ilian asks how we can experimentally test conscious processes. This moves the conversation to Feelings of Knowing (FOKs), which is one fundamental type of conscious experience. Bernie makes the point that Feelings of Knowing are an integral part of the conscious stream.
The next paper is by Gaillard et al. (2009). It is an outstanding example of reading work from France by Dehaene and Changeux in Paris. The title is “Converging Intracranial Markers of Conscious Access, ” and it represents probably the most precise evidence so far for cortical integration and broadcasting. The experiment compared conscious and unconscious processing of briefly flashed words. Alea explains how this evidence confirms that conscious perceptual activity is propagated widely throughout the cortex.
The third target paper is from a famous Yale epilepsy research group, led by Hal Blumenfeld, and the first author is Wendy X. Herman. It is titled, “A Switch and Wave of Neuronal Activity in the Cerebral Cortex During the First Second of Conscious Perception” (2019). Herman et al. discovered that stimuli that were consciously perceived elicited large-scale network switching, followed by waves of gamma activity. These findings support the hypothesis that such large waves are an indication of coordinated local-global activity.
An important recent paper by Deco et al. (2019) links this research to the major discovery of the cortical connectome, the street map of the cortex. It is called “Revisiting the Global Workspace.”
This fourth and final paper, with coauthors Deco, Vidaurre and Kringelbach, examined neuroimages from over 1000 participants and created a full brain hierarchy in what the researchers defined as ‘functional rich clubs.’ These ‘clubs’ correlate activity between brain regions and strengthen the idea that Global Workspace is dynamic, but not necessarily in a grossly visible way. Our trio explores: What does Deco’s idea of an “invariant global workspace” mean?
As our trio wraps up, Ilian wants to know about the future of “the quest for consciousness.” Bernie and Alea agree that combining brain recordings with phenomenological interviews during meditation is very exciting.