Ep 17: ”Global Workspace Theory: Exploring Evidence for Widespread Integration & Broadcasting of Conscious Signals - Part Two”

"I think in terms of consciousness, it seems to me that these Feelings of Knowing are perhaps the conscious tip of the iceberg for this huge amount of unconscious processing that's going on of all this information in our environment, where maybe I couldn't tell you why I know there's danger, but I know."

- Alea Skwara, PhD Candidate in the Perception, Cognition, and Cognitive Neuroscience (PCCN) area of the Psychology Department at UC Davis

 

Global Workspace Theory: Exploring Evidence for Widespread Integration & Broadcasting of Conscious Signals - Part Two

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. (2021) Revisiting the Global Workspace
• 1:26:29 – Functional Rich Clubs
• 1:41:50 – The Future Quest for Consciousness

 

Summary

Episode 17 is the second in a three-part series on GWT Origins & Evidence, featuring our student interviewers, Alea Skwara and Ilian Daskalov. Together with Bernard Baars, they examine the recent neuroscientific study of consciousness.

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.

 

Cortical Binding and Propagation

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, Alea and Ilian explore the question: What is the difference between an anatomical hub and a functional hub, and what does it mean to say that a functional hub is dynamic?

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.

 

Evidence for GWT: Conscious Access, Gamma Activity, and Functional Rich Clubs

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 and accurate evidence so far for cortical integration and broadcasting. The experiment compared conscious and unconscious processing of briefly flashed words. Our trio asks the question: How does the observed effect of longer lasting and more widespread brain activity during conscious perception of a word offer support for GWT?

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), and reinforces our message. Alea summarizes this third paper in the discussion, which looks at conscious perception in humans by using direct electrical recordings from the cerebral cortex during a visual perception task. 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. 

Our trio asks: What might be the special significance of the gamma and beta bands to consciousness?

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?

 

The Future Quest for Consciousness 

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.

 

Links to Papers Discussed in the Episode

Paper 1: “Global Workspace Dynamics: Cortical ‘Binding and Propagation’ Enables Conscious Contents

Paper 2: Converging Intracranial Markers of Conscious Access

Paper 3: A Switch and Wave of Neuronal Activity in the Cerebral Cortex During the First Second of Conscious Perception

Paper 4: Revisiting the Global Workspace: Orchestration of the Functional Hierarchical Organisation of the Human Brain

 

Bios

Alea Skwara is a PhD candidate at the University of California, Davis where she studies cognitive neuroscience. Her primary research focuses on compassion and responses to suffering. The main question that Alea is currently trying to answer is whether meditational practices can expand the range of people that a person can feel compassion for.

Ilian Daskalov is a senior undergraduate student at University of California, Irvine where he studies Cognitive Science. He holds an associate degree with honors from San Diego Mesa College. His research interests include sleep, psychedelics, and artificial intelligence. He is passionate about communicating science and promoting critical thinking. 

Bernard Baars is best known as the originator of global workspace theory and global workspace dynamics, a theory of human cognitive architecture, the cortex and consciousness. Bernie is a former Senior Fellow in Theoretical Neurobiology at the Neurosciences Institute in La Jolla, CA, and Editor in Chief of the Society for MindBrain Sciences. He is author of many scientific papers, articles, essays, chapters, and acclaimed books and textbooks.

 

Bernie is the recipient of the 2019 Hermann von Helmholtz Life Contribution Award by the International Neural Network Society, which recognizes work in perception proven to be paradigm changing and long-lasting.

 

He teaches science. It keeps him out of trouble.

 

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