Why are some mental processes conscious and others not? The brain runs thousands of operations in parallel — vision, motor control, balance, language, memory — almost all outside awareness. Yet a small handful of contents at any moment are conscious: the sentence I am reading, the itch on my arm, the worry that I will be late. In 1988, the cognitive scientist Bernard Baars proposed an architectural answer in A Cognitive Theory of Consciousness. The unconscious mind is a society of parallel local processors; consciousness is the moment a local result wins access to a global broadcast bus. Stanislas Dehaene and Jean-Pierre Changeux specified the broadcast neuronally over the next two decades, and global workspace theory has since become the most empirically productive framework in the cognitive neuroscience of consciousness — though not the only candidate, and not yet the settled answer.
The brain is modeled as many specialized modules running largely in parallel and largely unconsciously, plus a workspace whose function is to take the winning content of a moment and broadcast it to every other module. Consciousness, on this view, is not a place or substance but the functional state of being broadcast. Dehaene's neuronal version implements the workspace as long-range cortical pyramidal neurons in prefrontal, parietal, and anterior cingulate areas, whose distant projections allow a representation to ignite — a sudden, all-or-nothing, globally synchronized burst of activity that makes the represented content reportable. The temporal signature is a late positive event-related potential around 300 ms post-stimulus and gamma-band synchronization across distant cortical sites; below the threshold, sensory cortex still processes input but the workspace stays silent.
The theory has earned its standing through predictions experiments confirm. Masking studies — a brief stimulus overwritten before it can be reported — show the masked stimulus drives sensory cortex normally but fails to ignite the workspace; the signature is the dissociation, not the absence of activity. Attentional-blink paradigms show ignition by one target temporarily blocks ignition by a second. Disorders of consciousness (coma, deep anesthesia) show characteristic loss of long-range cortical integration; Massimini's Perturbational Complexity Index, which probes the brain with a TMS pulse and measures the complexity of the response, reliably distinguishes conscious from unconscious states. The field stays unsettled because GWT has serious competition. Integrated Information Theory identifies consciousness with a quantitative property of integration that very different substrates may share; higher-order theories require that a mental state be re-represented by another to be conscious; recurrent-processing theories locate consciousness in local sensory loops rather than frontoparietal broadcast. The Cogitate adversarial collaboration (2019+), a multi-lab preregistered test of GWT against IIT, has so far returned results partially favorable to each and decisive for neither. The Hard Problem of why broadcast or integration is accompanied by experience at all sits untouched.
GWT-inspired architectures are an active line in machine learning. Yoshua Bengio's Consciousness Prior and a wave of follow-on work explore neural networks with explicit workspace-style bottlenecks, motivated by the conjecture that current large language models lack the architectural analog of the global workspace and might benefit — in capability and interpretability — from acquiring one. Whether transformer attention already implements a partial broadcast bottleneck is an open question; most GWT theorists, Dehaene included, think current LLMs are not conscious because they lack the recurrent dynamics, embodiment, and global integration the theory specifies. Clinical applications of GWT-derived measures — the Perturbational Complexity Index, anesthesia-depth monitors, residual-awareness diagnostics in unresponsive patients — are now used in ICUs and have changed treatment in cases where standard bedside exams missed signs of consciousness.