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, and selective attention. Neural examples include coma and blindsight. Like other cognitive architectures, 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. The rest of the theater is dark and unconscious. 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, probably using corticocortical and corticothalamic fibers. This is the primary functional role of consciousness: 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 specialized 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; Edelman, 1989; Llinas & Ribary, 1992; Newman, this issue; Newman & Baars, 1993; Shallice, 1976; Posner, 1992).
Despite the whirl of controversy surrounding consciousness studies, there is real progress being made in cognitive science towards establishing an empirically-rigorous theory of mind, in both its conscious and non-conscious manifestations. Beginning with a broad overview of clinical and experimental findings bearing on the neural correlates of conscious processes, the author traces the development of several related models that appear to converge upon a central “conscious system”. This extended reticular-thalamic activating system (ERTAS) has been increasingly implicated in a variety of functions associated with consciousness, including: orienting to salient events in the outer world; dream (REM) sleep; the polymodal integration of sensory processes in the cortex (binding); selective attention, and volition. It is argued that the increasing convergence of models from clinical and experimental neuroscience is leading towards a general theory of consciousness which is both non-dualist and non-reductionist.
The temporal characteristics of the neural signalling believed to underlie consciousness are considered in the light of the master-module theory (Cotterill, 1995, 1996, 1997). It is suggested that consciousness is mediated by the flow of signals around what is referred to as the vital triangle, which comprises the sensory-processing areas of the cortex, the master module itself, and the thalamic intralaminar nuclei, these three regions forming a closed loop. The interactions between the apices of this triangle and other brain components are conjectured to provide consciousness with access to memory, and to produce the feelings known as qualia, to which the body's muscles contribute through what could be called internal reafference. It is also argued that consciousness is critically dependent on the carrier wave provided by oscillations in the gamma band, the amplitude modulation of which travels around the vital triangle. These new ideas are illustrated by reference to the cortical machinery involved in speech. The confinement of language processing to a single cerebral hemisphere is considered, and it is suggested that this unilateralization is a consequence of the fact that the muscles involved in articulation serve structures which cross the body's medial plane, and that these muscles therefore cannot be independently activated. An experiment is proposed which would test this explanation, though rather indirectly.
Broad spectrum philosophical resistance to physicalist accounts of conscious awareness has condensed around a single and clearly identified line of argument. Philosophical analysis and criticism of that line of argument has also begun to crystallize. The nature of that criticism coheres with certain theoretical ideas from cognitive neuroscience that attempt to address both the existence and the contents of consciousness. As well, experimental evidence has recently begun to emerge that will serve both to constrain and to inspire such theorizing. The present paper attempts to summarize the situation.
What must be admitted is that the definite images of traditional psychology form but the very smallest part of our minds as they actually live. The traditional psychology talks like one who should say a river consists of nothing but pailsful, spoonsful, quartpotsful, barrelsful, and other moulded forms of water. Even were the pails and the pots all actually standing in the stream, still between them the free water would continue to flow. It is just this free water of consciousness that psychologists resolutely overlook. Every definite image in the mind is steeped and dyed in the free water that flows round it. With it goes the sense of its relations, near and remote, the dying echo of whence it came to us, the dawning sense of whither it is to lead. The significance, the value, of the image is all in this halo or penumbra that surrounds and escorts it, —or rather that is fused into one with it and has become bone of its bone and flesh of its flesh; leaving it, it is true, an image of the same thing it was before, but making it an image of that thing newly taken and freshly understood.
Understanding consciousness as neural-level computation faces three problems: First, this approach generally overlooks certain brain features: a) “probabilistic” neurotransmitter release, b) dendritic microprocessing, c) electrotonic gap junctions, d) variability in reaction times/inherent apparent randomness, e) glia, and f) the role of intraneuronal cytoskeletal microtubules. The second problem is computation itself. Present-day computers may be evolving toward quantum computing, in which elements compute in quantum superposition of different possible states (“qubits”), and reduce (collapse) computably to a solution. If the brain/mind is anything like a computer, it is most likely some kind of self-organizing quantum computer. The third problem is the inability of conventional neural approaches to deal with the problem of conscious experience, or qualia (as well as unitary binding, free will, non-computability, and the transition from pre-conscious to conscious processes). New approaches are needed. The Penrose-Hameroff model suggests that quantum superpositions and Penrose's objective reductions occur in microtubules in groups of brain neurons and glia interconnected by gap junctions. The proposed microtubule quantum states and cycles of self-collapses are isolated by actin gelation, orchestrated by microtubule-associated proteins, and coupled to neural-level activity (e.g. coherent 40 Hz). The model predicts that the orchestrated objective reduction (“Orch OR”) events access and select “funda-mental” experience embedded in Planck scale spacetime geometry, and choose (non-computably) microtubule states which regulate neural activity. Consciousness may involve neurobiological processes extending downward within neurons to the level of the cytoskeleton, and accessing fundamental experience at the most basic level of reality.
Neural correlates of consciousness (NCC) with a special reference to visual awareness elicited by motion after effect (MAE) was investigated using neuroimaging method (SQUID). MAE is a negative after effect caused by prolonged viewing of real visual motion: After gazing at a moving pattern for a while, a stationary image will appear to move in the opposite direction. Evoked magnetic field (magnetoencephalogram; MEG) was measured when a subject observing MAE in which concentric circles appear to continuously contracting after viewing the rings moving in a single local direction (continuously expanding motion). Magnetic evoked field at latency of 182 ms was averaged from 37 cortical points over occipital, temporal and parietal areas during observing MAE after adaptation period of 5 s with low spatial frequency. MRI (Magnetic Resonance Imaging) brain image and measured dipole locus was fitted for each subject. The results clearly indicated the main unitary locus subserving visual awareness due to MAE and real motion, i.e., both illusory and real visual awareness, appear to be surrounding region over lateral occipito-temporal area in the human brain which is close to MT area.
Pictures that spontaneously change in appearance, such as depth or figure-ground reversals, have always been thought of as powerful tools for understaning the nature of the perceptual system. The cause of the perceptual multistability that is experienced when viewing such figures most likely lies in the brain's physical organization; an organization that imposes several constraints on the processing of visual information. Why is it that our visual system fails to lock onto one aspect of an ambiguous figure? What accounts for the spontaneous changes of interpretation? What are the neural events that underlie such changes? Are there neurons in the visual pathways the activity of which reflects the visual awareness of the stimulus? In my paper I describe some combined psychophysical and physiological experiments that were motivated by these questions. In specific, we report on experiments in which neural activity in early visual cortex and in the inferior temporal cortex of monkeys was studied, while the animals experienced binocular rivalry. Our results provide us with new evidence not only on the neural mechanisms of binocular rivalry (one example of multistable perception), but also on the neural processes underlying image segmentation and perceptual grouping.
Diverse types of chaos have been confirmed at several hierarchical levels in the real neural systems. The role of chaos in actual perceptual processes should be investigated energetically. In this paper, we present a perception model of ambiguous patterns based on the chaotic neural networks with the refractoriness and the time-hysteresis, from the viewpoint of bottom-up approach. Computer simulations reproduce the Gamma distributions obtained in psychophysical experiments. This is difficult for the stochastic activity to attain to. In addition, we refer to a dynamic picture regarding the chaotic trembling mode as the small involuntary perceptual movement.
Despite roboticists' endeavours to endow their robots with cognition, robots do not exhibit as complex interactive behaviours as those of their animal counterparts. Our belief is that this failure partially originates from a lack of self-awareness of those robots. Indeed, it is difficult for a robot which cannot discriminate between his own body and its environment or understand his physical configuration to map the behaviours of other agents living in its environment onto his body and therefore exhibit social communication such as imitation (unless such a mapping is explicitely encoded in its behavior). We address here a particular aspect of self-awareness, namely self-recognition, because self-recognition reveals an awareness of stable categorical features of self. The understanding of self-recognition in nonhumans primates has been recently extensively studied and some well-defined experimental tests have been proposed. However, no model has been proposed, partly because, from a psychological point of view, it is difficult to estimate the bias of hidden factors inherent to the experimental setup in the inference of a mechanism. Robotics instead provides an alternative mean for testing theories of behavior, by implementing tentative mechanisms and analyzing the obtained behaviours along lines similar to those used for analyzing animal behaviours. In this paper, we review some work done in self-recognition in nonhuman primates and we propose a framework for exploring this process on a robot.