Mind Matters Natural and Artificial Intelligence News and Analysis
human-brain-stockpack-adobe-stock
Human brain

GWT: A Leading Consciousness Theory Depends on Information Theory

Not mechanism. If Global Workspace Theory (GWT) is a good approach to consciousness, there is no “consciousness spot” in the brain.

Recently, we have looked at the Integrated Information Theory (IIT) of human consciousness, as set out by well-known Allen Institute neuroscientist Christof Koch. Another leading contender (and rival) is Global Workspace Theory (GWT) — it pictures the brain as an orchestra with many conductors.

IIT is panpsychist in orientation (the universe participates in consciousness; human consciousness is the most highly developed instance) whereas GWT uses information theory to capture an image of consciousness via observations of the brain at work.

A recent essay in Psyche by two GWT proponents, Morten L. Kringelbach and Gustav Deco, introduces us to GWT:

… given the distributed nature of the brain hierarchy, there is unlikely to be just a single ‘conductor’. Instead, in 1988 the psychologist Bernard Baars proposed the concept of a ‘global workspace’, where information is integrated in a small group of brain regions (or ‘conductors’) before being broadcast to the whole brain…

Colloquially, the brain’s global workspace is thus akin to a small core assembly of people in charge of an organisation: like a group of Herbert von Karajans conducting a musical orchestra.

Morten L Kringelbach and Gustavo Deco, “The brain has a team of conductors orchestrating consciousness” at Psyche (October 6, 2021)

Oxford neuroscientist Morten L Kringelbach is the author of Emotion: Pain and Pleasure in the Brain (2014), co-authored with Helen Phillips. Gustavo Deco, director of the Center of Brain and Cognition in Barcelona, is the author of The Noisy Brain (2010), co-authored with Edmund T Rolls. Together, Kringelbach and Deco published an open-access paper this year in Nature Human Behaviour, in which they identified the brain regions of 1000 participants that they hypothesize are a “global workspace” (the “functional rich club”) of conductors:

This much-celebrated theory proposed an elegant solution to the problem of how hierarchical organisation allows the brain to orchestrate function and behaviour by organising the flow of information and the underlying computations necessary for survival. As such, this is a theory of consciousness, as pointed out by the neuroscientists Stanislas Dehaene, Michael Kerszberg and Jean-Pierre Changeux, who in 1998 proposed their modification: the global neuronal workspace hypothesis, where associative perceptual, motor, attention, memory and value areas interconnect to form a higher-level unified space in which information is broadly shared and broadcast back to lower-level processors. Colloquially, the brain’s global workspace is thus akin to a small core assembly of people in charge of an organisation: like a group of Herbert von Karajans conducting a musical orchestra.

Morten L Kringelbach and Gustavo Deco, “The brain has a team of conductors orchestrating consciousness” at Psyche (October 6, 2021)

In their model, at a high level, the brain’s conductors fuse information from the senses with memories. The processing “is further influenced by reward and expectations and by any surprising deviations from previous experiences.”

Much progress has been made in understand the brain’s anatomical wiring. But here’s the puzzle. It’s not critical to information flow:

This research has provided important insights into the brain’s anatomical hierarchy. At the same time, each brain region has different and specific local dynamics, which gives rise to the unconstrained nature of functional information flow, which is thus shaped but not fully determined by the underlying anatomy. What ultimately matters for determining the orchestration of brain function is the dynamic changes in functional information flow.

Morten L Kringelbach and Gustavo Deco, “The brain has a team of conductors orchestrating consciousness” at Psyche (October 6, 2021)

A moment earlier, the authors had stressed,

The information flow within this hierarchy is highly dynamic; not just bottom-up but also top-down. In fact, recurrent interactions shape the functional processing underlying cognition and behaviour. Much of this information flow follows the underlying anatomy in the structural connections between brain regions but, equally, the information flow is largely unconstrained by this anatomical wiring.

Morten L Kringelbach and Gustavo Deco, “The brain has a team of conductors orchestrating consciousness” at Psyche (October 6, 2021)

Well then, if information flow in the brain is “largely unconstrained” by anatomical wiring, it’s easy to understand why we sense that we have “minds” apart from our brains.

The Global Workspace theorists decided to adopt an information theory approach to the problem: “We turned to the framework of transfer entropy, which is an information-theoretic measure that can capture the causal flow of information, ie how activity in a given region can be shown to causally influence activity in another. Ultimately, the framework was able to provide us with the information flow between all brain regions, which in turn allowed us to study the functional hierarchical organisation and how this relates to anatomy.” That’s where their concept of a “functional rich club” or FRIC (a French word for money) comes in: “a dynamic measure based on bidirectional flow of information not constrained by anatomy and thus changing across different tasks.”:

To use our earlier metaphor from orchestral music, the leading role of ‘conductor’ is taken up by a group of different musicians serving as ‘hubs’. Some of these musicians will remain conductors, regardless of the kind of concert, just as different sections of a real orchestra retain the first violinist and first cellist. (In reality, the conductor is only rarely selected from the existing musicians within an actual orchestra. However, the brain’s economy is such that it can’t afford to bring in a von Karajan as the overall conductor of everything.)

Morten L Kringelbach and Gustavo Deco, “The brain has a team of conductors orchestrating consciousness” at Psyche (October 6, 2021)

Wait. Why can’t the brain “afford“ a von Karajan-type conductor? ? Isn’t the point rather that the brain doesn’t need him? If GWT is a good theory, one outcome is that there is no “consciousness spot” in the brain. Finding the consciousness spot within 25 years was the basis of a 1998 science wager between two famous figures in consciousness studies (Christof Koch and David Chalmers) and it has only two more years to run…

The GWT researchers are careful to emphasize that they perceive the relationship between the parts of the brain that they believe are responsible for consciousness as “mechanistic”:

Using this method, we discovered that the global workspace consists of a core subset of brain regions, which include the precuneus, the posterior and isthmus cingulate, nucleus accumbens, putamen, hippocampus and amygdala (see figure below). This core functional ‘club’ of integrative brain regions is consistent with the original proposal by Dehaene, Kerszberg and Changeux, which suggests that the global neuronal workspace must integrate past and present through focusing and evaluation.

Morten L Kringelbach and Gustavo Deco, “The brain has a team of conductors orchestrating consciousness” at Psyche (October 6, 2021)
The hydra was a mythical snake, pictured here on a pottery jug from 525 BC. When a head was cut off, it grew two more/Wolfgang Sauber ( GNU Free Documentation License, Version 1.2).

But then they also report,

We demonstrated that lesioning the regions of the global workspace in the whole-brain model significantly impaired the brain’s ability to function. However, we also showed that the brain is like a multiheaded hydra that can still function with one or two heads cut off. This demonstrates the robustness and resilience of the human brain in adversity, and the ways in which the conductors can take on extra responsibilities if needed.

Morten L Kringelbach and Gustavo Deco, “The brain has a team of conductors orchestrating consciousness” at Psyche (October 6, 2021)

That’s not very mechanistic, really. They then, in closing, invoke self-organization theory:

A direct consequence of our new finding is that it is now clear that the immense chaos arising in complex systems can be carefully orchestrated by a small subset of ‘conductors’, self-organising from the constituent parts. Unlike musical orchestras that are much enhanced by a brilliant von Karajan, the great resilience of the brain’s orchestration is that it relies on the concerted efforts of a small subset of agile and adaptable conductors in its global workspace.

Morten L Kringelbach and Gustavo Deco, “The brain has a team of conductors orchestrating consciousness” at Psyche (October 6, 2021)

A reader may find the authors’ model a curious one: A team of conductors is much more complex than an imposing von Karajan. The fact that such a system could come into being at all — laden with excellent opportunities for decisive early failure — is, in itself, remarkable. However, their decision to rely on information theory as a source of models sounds like a wise one.

In 2019, Templeton World Charities organized a contest, of sorts, between Global Workspace Theory (GWT) and Integrated Information Theory (IIT) though the COVID-19 pandemic seems to have delayed it somewhat. It will certainly be one to watch.

You may also wish to read: Quick facts on IIT, the leading theory of consciousness (if not tied with Global Workspace Theory). IIT may be part of a trend in science in which emergence and panpsychist theories are slowly replacing materialist and physicalist ones. Note that GWT is not very firmly tied to mechanism or materialism either.

Also: A theoretical physicist grapples with the math of consciousness. Sabine Hossenfelder is not very happy with what she sees. Even for the brain of a worm, the best theory on offer would, she says, take several billion years to calculate. That can’t be the right answer.


Mind Matters News

Breaking and noteworthy news from the exciting world of natural and artificial intelligence at MindMatters.ai.

GWT: A Leading Consciousness Theory Depends on Information Theory