van der Velde & de Kamps make a case for neural blackboard architectures to address four questions raised by human language. Unfortunately, they neglect a sizable literature relating blackboard architectures to other fundamental cognitive questions, specifically consciousness and voluntary control. Called “global workspace theory,” this literature integrates a large body of brain and behavioral evidence to come to converging conclusions.
Neural Darwinism (ND) is a large scale selectionist theory of brain development and function that has been hypothesized to relate to consciousness. According to ND, consciousness is entailed by reentrant interactions among neuronal populations in the thalamocortical system (the ‘dynamic core’). These interactions, which permit high-order discriminations among possible core states, confer selective advantages on organisms possessing them by linking current perceptual events to a past history of value-dependent learning. Here, we assess the consistency of ND with 16 widely recognized (...) properties of consciousness, both physiological (for example, consciousness is associated with widespread, relatively fast, low amplitude interactions in the thalamocortical system), and phenomenal (for example, consciousness involves the existence of a private flow of events available only to the experiencing subject). While no theory accounts fully for all of these properties at present, we find that ND and its recent extensions fare well. (shrink)
The standard behavioral index for human consciousness is the ability to report events with accuracy. While this method is routinely used for scientific and medical applications in humans, it is not easy to generalize to other species. Brain evidence may lend itself more easily to comparative testing. Human consciousness involves widespread, relatively fast low-amplitude interactions in the thalamocortical core of the brain, driven by current tasks and conditions. These features have also been found in other mammals, which suggests that consciousness (...) is a major biological adaptation in mammals. We suggest more than a dozen additional properties of human consciousness that may be used to test comparative predictions. Such homologies are necessarily more remote in non-mammals, which do not share the thalamocortical complex. However, as we learn more we may be able to make “deeper” predictions that apply to some birds, reptiles, large-brained invertebrates, and perhaps other species. (shrink)
The metacognitive stance of Smith et al. (2003) risks ignoring sensory consciousness. Although Smith et al. rightly caution against the tendency to preserve the uniqueness of the human mind at all costs, their reasoned stance is undermined by a selective association of consciousness with high-level cognitive operations. Neurobiological evidence may offer a more general, and hence more inclusive, basis for the systematic study of animal consciousness.
Conscious perception, like the sight of a coffee cup, seems to involve the brain identifying a stimulus. But conscious input activates more brain regions than are needed to identify coffee cups and faces. It spreads beyond sensory cortex to frontoparietal association areas, which do not serve stimulus identification as such. What is the role of those regions? Parietal cortex support the ‘first person perspective’ on the visual world, unconsciously framing the visual object stream. Some prefrontal areas select and interpret conscious (...) events for executive control. Such functions can be viewed as properties of the subject, rather than the object, of experience – the ‘observing self’ that appears to be needed to maintain the conscious state. (shrink)
The limited capacity of immediate memory “rides” on the even more limited capacity of consciousness, which reflects the dynamic activity of the thalamocortical core of the brain. Recent views of the conscious narrow-capacity component of the brain are explored with reference to global workspace theory (Baars 1988; 1993; 1998). The radical limits of immediate memory must be explained in terms of biocognitive brain architecture.
Surgical patients under anesthesia can wake up unpredictably and be exposed to intense, traumatic pain. Current medical techniques cannot maintain depth of anesthesia at a perfectly stable and safe level; the depth of unconsciousness may change from moment to moment. Without an effective consciousness monitor anesthesiologists may not be able to adjust dosages in time to protect patients from pain. An estimated 40,000 to 200,000 midoperative awakenings may occur in the United States annually. E. R. John and coauthors present the (...) scientific basis of a practical ''consciousness monitor'' in two articles. One article is empirical and shows widespread and consistent electrical field changes across subjects and anesthetic agents as soon as consciousness is lost; these changes reverse when consciousness is regained afterward. These findings form the basis of a surgical consciousness monitor that recently received approval from the U.S. Food and Drug Administration. This may be the first practical application of research on the brain basis of consciousness. The other John article suggests theoretical explanations at three levels, a neurophysiological account of anesthesia, a neural dynamic account of conscious and unconscious states, and an integrative field theory. Of these, the neurophysiology is the best understood. Neural dynamics is evolving rapidly, with several alternative points of view. The field theory sketched here is the most novel and controversial. (shrink)
?In everday language, the word ?attention? implies control of access to consciousness, and we adopt this usage here. Attention itself can be either voluntary or automatic. This can be readily modeled in the theory. Further, a contrastive analysis of spontaneously self?attributed vs. self?alien experiences suggests that ?self? can be interpreted as the more enduring, higher levels of the dominant context hierarchy, which create continuity over the changing flow of events. Since context is by definition unconscious in GW theory, self in (...) this sense is thought to be inherently unconscious as well. This proposal is consistent with a great deal of objective evidence. However, aspects of self may become known through ?conscious self-monitoring,? a process that ??is useful for self-evaluation and self?control. The results of conscious self-monitoring are combined with self?evaluation criteria, presumably of social origin, to produce a stable ?self?concept?, which functions as a supervisory system within the larger self organization. (shrink)
This paper explores a remarkable convergence of ideas and evidence, previously presented in separate places by its authors. That convergence has now become so persuasive that we believe we are working within substantially the same broad framework. Taylor's mathematical papers on neuronal systems involved in consciousness dovetail well with work by Newman and Baars on the thalamocortical system, suggesting a brain mechanism much like the global workspace architecture developed by Baars (see references below). This architecture is relational, in the sense (...) that it continuously mediates the interaction of input with memory. While our approaches overlap in a number of ways, each of us tends to focus on different areas of detail. What is most striking, and we believe significant, is the extent of consensus, which we believe to be consistent with other contemporary approaches by Weiskrantz, Gray, Crick and Koch, Edelman, Gazzaniga, Newell and colleagues, Posner, Baddeley, and a number of others. We suggest that cognitive neuroscience is moving toward a shared understanding of consciousness in the brain. (shrink)
The study of conscious experience has seen remarkable strides in the last ten years, reflecting important technological breakthroughs and the enormous efforts of researchers in disciplines as varied as neuroscience, cognitive science, and philosophy. Although still embroiled in debate, scientists are now beginning to find common ground in their understanding of consciousness, which may pave the way for a unified explanation of how and why we experience and understand the world around us. Written by eminent psychologist Bernard J. Baars, Inside (...) the Theater of Consciousness: The Workspace of the Mind brings us to the frontlines of this exciting discipline, offering the general reader a fascinating overview of how top scientists currently understand the processes underlying conscious experience. Combining psychology with brain science, Baars brilliantly brings his subject to life with a metaphor that has been used to understand consciousness since the time of Aristotle--the mind as theater. Here consciousness is seen as a "stage" on which our sensations, perceptions, thoughts, and feelings play to a vast, silent audience (the immensely complicated inner-workings of the brain's unconscious processes). Behind the scenes, silent context operators shape conscious experience; they include implicit expectations, self systems, and scene setters. Using this framework, Baars presents compelling evidence that human consciousness rides on top of biologically ancient mechanisms. In humans it manifests itself in inner speech, imagery, perception, and voluntary control of thought and action. Topics like hypnosis, absorbed states of mind, adaptation to trauma, and the human propensity to project expectations on uncertainty, all fit into the expanded theater metaphor. As Baars explores our present understanding of the mind, he takes us to the top laboratories around the world, where we witness some of the field's most exciting breakthroughs and discoveries. (For instance, Baars recounts one extraordinary sequence of experiments, in which state-of-the-art PET scans--reproduced here in full color--capture in fascinating, graphic detail how brain activity changes as people learn how to play the computer game Tetris.) And throughout the book, Baars has sprinkled numerous and often highly amusing on-the-spot demonstrations that illuminate the ideas under discussion. Understanding consciousness is perhaps the most difficult puzzle facing the sciences today. In the Theater of Consciousness offers an invaluable introduction to the field, brilliantly weaving together the various theories that have emerged as scientists continue their quest to uncover the profound mysteries of the mind--and of human nature itself. (shrink)
1.1 Bilateral damage to the thalamus abolishes waking consciousness. The critical site of this damage is believed to be a relatively small cluster of neurons, about the size of a pencil eraser on either side of the brain's midline, called the Intra-Laminar Nuclei (ILN) because they are located inside the white layers (laminae) that divide the two thalami into their major groupings of nuclei. The fact that bilateral damage to the ILNs abolishes consciousness is very unusual. There is no other (...) site in the brain that has this property, except the reticular formation in the brain stem. In contrast, huge chunks of cortex can be damaged without abolishing the STATE of consciousness. (Cortical damage does change the CONTENTS of consciousness, of course). (shrink)
The world of our experience consists at all times of two parts, an objective and a subjective part . . . The objective part is the sum total of whatsoever at any given time we may be thinking of, the subjective part is the inner 'state' in which the thinking comes to pass.
Conscious experience is one of the most difficult and thorny problems in psychological science. Its study has been neglected for many years, either because it was thought to be too difficult, or because the relevant evidence was thought to be poor. Bernard Baars suggests a way to specify empirical constraints on a theory of consciousness by contrasting well-established conscious phenomena - such as stimulus representations known to be attended, perceptual, and informative - with closely comparable unconscious ones - such as (...) stimulus representations known to be preperceptual, unattended, or habituated. Adducing data to show that consciousness is associated with a kind of global workplace in the nervous system, and that several brain structures are known to behave in accordance with his theory, Baars helps to clarify many difficult problems. (shrink)
