|Bernard J. Baars and Katherine McGovern|
Global Workspace theory is a simple cognitive architecture that has been developed to account qualitatively for a large set of matched pairs of conscious and unconscious processes (Baars, 1983, 1988, 1993, 1997). Such matched contrastive pairs of phenomena can be either psychological or neural. Psychological phenomena include subliminal priming, automaticity with practice, selective attention, and many others. Neural examples include coma and blindsight. Like other cognitive architectures (Newell, 1990), GW theory may be seen in terms of a theater metaphor of mental functioning. Consciousness resembles a bright spot on the theater stage of Working Memory (WM), directed there by a spotlight of attention, under executive guidance (Baddeley, 1992). The rest of the theater is dark and unconscious. "Behind the scenes" are contextual systems, which shape conscious contents without ever becoming conscious, such as the dorsal cortical stream of the visual system.
This architectural approach leads to specific neural hypotheses. For sensory consciousness the bright spot on stage is likely to require the corresponding sensory projection areas of the cortex. Sensory consciousness in different modalities may be mutually inhibitory, within approximately 100-ms time steps.
Sensory cortex can be activated internally as well as externally, resulting in conscious inner speech and imagery. Once a conscious sensory content is established, it is broadcast widely to a distributed "audience" of expert networks sitting in the darkened theater, using corticocortical and corticothalamic fibers. Among the experts behind the scenes are "self-systems," viewed as contextual data structures that both shape and receive information from the bright spot; they include parts of prefrontal cortex, but may range posteriorly as far as parietal cortex for visual orientation.
The primary functional role of consciousness is to allow a "blackboard" architecture to operate in the brain, in order to integrate, provide access, and coordinate the functioning of very large numbers of special- ized networks that otherwise operate autonomously (Mountcastle, 1978). All the elements of GW theory have reasonable brain interpretations, allowing us to generate a set of specific, testable brain hypotheses about consciousness and its many roles in the brain. This approach is compatible with a number of other proposals (Crick, 1984; Crick & Koch, 1990; Damasio, 1989; LaBerge, 1997; Gazzaniga, 1996; Ramachandran, 1995; Edelman, 1989; Llinas & Ribary, 1992; Newman & Baars, 1993; Shallice, 1976; Posner, 1992).
Bernard J. Baars and Katherine McGovern
The Wright Institute
See Baars, Bernard J. (2003). The global brainweb: An update on global workspace theory.
Guest editorial, Science and Consciousness Review, October 2003. Full text.
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Critiques of Global Workspace Theory
Francis F. Steen, Communication Studies, University of California, Los Angeles