Glossary of Terms for GWT: Origins & Evidence

Conscious vs. Unconscious Events

For the time being, we will refer to our common sense meanings of conscious and unconscious brain functions. During waking, we experience the world consciously, during sleep, we do not. That is our first overview. However, during the waking state most specialized regions of the brain continue to function unconsciously. Conscious events are shaped by unconscious frames.

Conscious Brain

Sensory consciousness is profoundly embedded in biology, anatomy, physiology, and above all, in adaptive brain functions that serve us in every second of waking life. This is not some abstract speculation. It is now supported by numerous empirical findings published in peer-reviewed journals that are easily found in web archives.

Adaptive Resonance

Almost all the connections in the cortex are bidirectional, like a two-way highway. In the cortex, neural signals, therefore, tend to show resonance rather than one-way traffic. This tends to baffle brain scientists, but it now seems that “resonant signaling” is key to the adaptive capacities of the cortex. “Resonance” is an enormously powerful information processing style of the cortex. “Adaptive Resonance” seems to be the basis for the enormous adaptability of cortex.

The trajectory of cortical functioning seems to walk a very fine line. Local resonances can disturb healthy functioning, like an epileptic seizure. But normal waking has to serve basic functions, like sensation, perception, action, and memory in a very precise way.

Gerald Edelman proposed that the cortex functions “near criticality” like a high wire acrobat in a circus, ready to jump in many different directions while maintaining balance.

Near Criticality

Brain theorists have long wondered about a very fast switching rate between stable and chaotic and chaotic states in cortex. In engineering, this is called “near critical functioning.” A tightrope walker stays safe in a very delicate balance, so as to move forward toward a goal, while not falling off. The dynamical cortex runs in much the same way, ready to adapt in a moment, while moving towards its goal.

Oscillations

The instantaneous operations of the brain are reflected in their electrical signature, which can be recorded, either from outside, or from implanted electrodes. These oscillations tell us about signal processing in the brain.

The Bridge: The Corpus Callosum

The two hemispheres of the brain look separate, but so do the two neighborhoods of a city divided by a river. Geography tells us of appearance, but the traffic flow shows how things actually work. The corpus callosum is an enormous bridge between the two giant hemispheres. The healthy brain looks divided, like a city, but it works as a unified system.

Composed of about 200 million axons interconnecting the brain’s two hemispheres, its primary function is to integrate motor, sensory, and cognitive performances between the cerebral cortex on one side of the brain to the same region on the other side. The left hemisphere is usually involved in speaking, but in the intact brain the hemispheres are constantly communicating with each other. The brain can even heal itself after major disruptions.

Global Workspace Theory (GWT)

Global Workspace Theory (GWT) is a theory of human cognitive architecture, the cortex, and consciousness. In the most basic terms, GWT is a set of testable hypotheses about how conscious experiences arise from the brain, and is a widely used scientific model for the role of conscious and unconscious events for several decades (Baars, 1988; Baars & Geld, 2019).

GWT started in the 1980s as a purely psychological theory of conscious cognition, and has become a prominent approach in scientific studies of consciousness (Mashour et al., 2020).

Based on today’s far more detailed understanding of the brain, GWT has adapted to new waves of evidence. The brain-based version of GWT is called Global Workspace Dynamics (GWD) precisely because the cortex is viewed as a “unified oscillatory machine” (Steriade, 1999). A brain-based global workspace integrates many sources of information into a single conscious gestalt, and then propagates that summarized gestalt to other parts of the brain.

GWT therefore joins other theories in viewing consciousness as the product of highly integrated and widespread cortico-thalamic (C-T) activity, following a long trail of evidence (Dehaene et al., 1998).

Connectome

The connectome reveals the major street map of the cortex. It is a very important new insight. The “functional connectome” shows how brain signals travel over that street map. We can think of the connectome as a “wiring diagram.”

An organism’s nervous system is made up of neurons which link through synapses. The brain’s version of a global workspace must unify that street map from one experience to the next.

Excitatory & Inhibitory Neurons

Over a hundred billion neurons in the brain are either excitatory or inhibitory. An excitatory neuron signals the next nerve cell to fire. An inhibitory neuron tells the next nerve cell not to fire. Every state of the brain is a balance between excitation and inhibition.

Neural Darwinism

The late Nobelist Gerald M. Edelman proposed that brain functioning at many, many levels follows the logic of “Neural Darwinism”. The brain is not a computer, but it is a “Selectionist” biological organ much like the evolution of life itself.

Stream of Consciousness (SoC)

If you close your eyes and allow yourself to relax, you might observe your thoughts jumping from one topic to another. This apparently spontaneous Stream of Consciousness (SoC) was famously described as the bird-like “flights” and “perches” of conscious ideas, by William James. 

The SoC is explained in Global Workspace theory as an ongoing interplay between conscious contents and unconscious frames, especially goal frames in the process of solving spontaneously posed questions.

Brain Rhythms

A century ago, scientists were baffled to observe electrical rhythms radiating from the brain. Today we know that brain rhythms can range from very slow to very fast frequencies, much like radio waves. The slowest waves are about the pace of a heartbeat, and the fastest waves go up to two hundred times per second. Most signaling in the brain is somewhere in the middle. We are still learning about the different functions of various waveforms.

Default Mode Network (DMN)

The default mode network (DMN) is a network of interacting brain regions that is active when a person is not focused on an effortful task, and the brain is at wakeful rest, such as during daydreaming and spontaneous thought.

The DMN is also active when we are thinking about other people, about ourselves, and about our past and future.

Accurate Voluntary Report

What is consciousness? This question is discussed endlessly, but scientists have always focused initially on a simple observational definition.

For consciousness, accurate voluntary report has been extremely useful in the sensory sciences for more than two centuries. Under good experimental conditions, we can also use the same definition for conscious inner speech, conscious visual imagery, and conscious ideas.

Central Limited Capacity

Consciousness is associated with a central “bottleneck” in mental processing, as shown by selective attention, competing tasks, and the limits of immediate memory. By contrast, UNconscious specialized processors, taken together, have much greater processing capacity.

This central “bottleneck” in mental processing includes volition, feelings of knowing (FOKs), and conscious sensory percepts. The problem is that competing tasks tend to interfere with each other, but conscious animals cannot afford to stop and think when they are being chased by a predator.

“Ignition” or “Broadcasting” of Conscious Contents

When you select one stream of conscious input out of a hundred, we observe an “ignition” in the relevant part of the brain: a “broadcast” in GWT terminology. The information from that particular conscious event spreads or “propagates” as soon as it becomes conscious, and that has now been confirmed by a experiments in brain science.

Bidirectional Traffic Flow in cortex

Bidirectional traffic signaling is the standard working mode for the waking cortex; both the outer cortical helmet of the neocortex and the inner double-horned hippocampus, which is wrapped in the two temporal lobes at the sides of the brain. The basic fact that the wiring of the cortex and thalamus is bidirectional. (If neuron A leads to B, B will generally also lead to A.)

The Global Workspace is DYNAMIC

Many people misunderstand GWT to predict a single anatomical center in the brain. The global workspace is dynamic. The brain is so flexible, it does not need a single fixed location, any more than the world wide web needs a single fixed location to spread information from one computer to all the others.