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John, E. Roy

doi:10.1006/ccog.2001.0517

Cited by 2 publications

(2 citation statements)

References 23 publications

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“…Both sleep and waking are under precise homeostatic state control (John et al, 2001), controlled by thalamocortical circuits timed by basal brain nuclei. More than 200 types of epigenetic expression accompany sleep and waking in rats, suggesting many basic biological functions.…”

Section: States and Contentsmentioning

confidence: 99%

“…Neural computations can be remarkably flexible, and is, to some degree, independent of specific cells and populations. John et al (2001) has argued that active neuronal populations must have dynamic turnover to perform any single brain function, like active muscle cells. Edelman and Tononi (2000) and others have made the same point with the concept of a dynamic core.…”

Section: Introductionmentioning

confidence: 99%

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Global Workspace Dynamics: Cortical “Binding and Propagation” Enables Conscious Contents

Baars¹,

Franklin²,

Ramsøy³

2013

Front. Psychol.

214

204

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A global workspace (GW) is a functional hub of binding and propagation in a population of loosely coupled signaling elements. In computational applications, GW architectures recruit many distributed, specialized agents to cooperate in resolving focal ambiguities. In the brain, conscious experiences may reflect a GW function. For animals, the natural world is full of unpredictable dangers and opportunities, suggesting a general adaptive pressure for brains to resolve focal ambiguities quickly and accurately. GW theory aims to understand the differences between conscious and unconscious brain events. In humans and related species the cortico-thalamic (C-T) core is believed to underlie conscious aspects of perception, thinking, learning, feelings of knowing (FOK), felt emotions, visual imagery, working memory, and executive control. Alternative theoretical perspectives are also discussed. The C-T core has many anatomical hubs, but conscious percepts are unitary and internally consistent at any given moment. Over time, conscious contents constitute a very large, open set. This suggests that a brain-based GW capacity cannot be localized in a single anatomical hub. Rather, it should be sought in a functional hub -a dynamic capacity for binding and propagation of neural signals over multiple task-related networks, a kind of neuronal cloud computing. In this view, conscious contents can arise in any region of the C-T core when multiple input streams settle on a winner-take-all equilibrium. The resulting conscious gestalt may ignite an any-to-many broadcast, lasting ∼100-200 ms, and trigger widespread adaptation in previously established networks. To account for the great range of conscious contents over time, the theory suggests an open repertoire of binding 1 coalitions that can broadcast via theta/gamma or alpha/gamma phase coupling, like radio channels competing for a narrow frequency band. Conscious moments are thought to hold only 1-4 unrelated items; this small focal capacity may be the biological price to pay for global access. Visuotopic maps in cortex specialize in features like color, retinal size, motion, object identity, and egocentric/allocentric framing, so that a binding coalition for the sight of a rolling billiard ball in nearby space may resonate among activity maps of LGN, V1-V4, MT, IT, as well as the dorsal stream. Spatiotopic activity maps can bind into coherent gestalts using adaptive resonance (reentry). Single neurons can join a dominant coalition by phase tuning to regional oscillations in the 4-12 Hz range. Sensory percepts may bind and broadcast from posterior cortex, while non-sensory FOKs may involve prefrontal and frontotemporal areas. The anatomy and physiology of the hippocampal complex suggest a GW architecture as well. In the intact brain the hippocampal complex may support conscious event organization as well as episodic memory storage.

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Section: States and Contentsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Global Workspace Dynamics: Cortical “Binding and Propagation” Enables Conscious Contents

Baars¹,

Franklin²,

Ramsøy³

2013

Front. Psychol.

214

204

View full text Add to dashboard Cite

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Current concepts of consciousness with some implications for anesthesia

Baars

2003

Can J Anesth/J Can Anesth

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HERE is now extensive evidence that consciousness is associated with brainwide distribution and integration of information. Psychological evidence for the hypothesis was summarized by Baars (1988Baars ( , 1997Baars ( , 2002 in a framework called Global Workspace (GW) theory, derived from the cognitive architecture tradition. The global hypothesis has implications for perception, emotion, motivation, learning, working memory, voluntary control, and self systems in the brain. Recent brain imaging evidence appears to be broadly supportive, and the hypothesis is now favoured by philosophers like Daniel C. Dennett and Ned Block. The GW hypothesis is directly testable by brain scanning experiments that treat consciousness as a variable. Implications for unconscious states, including general anesthesia, are discussed.T Th he e r re ed di is sc co ov ve er ry y o of f c co on ns sc ci io ou us sn ne es ss s Shortly after 1,900 behaviourists attempted to purge science of mentalistic concepts like consciousness, attention, memory, imagery and voluntary control. "Consciousness," wrote John B. Watson, "is nothing but the soul of theology." But as the facts accumulated over the 20th century, all the traditional ideas were found to be necessary. They were reintroduced with more testable definitions. Memory came back in the 60's; imagery in the 70's; selective attention in the last half century; and consciousness in the last decade or so.It is roughly true that what we are conscious of is what we can report with accuracy. Conscious brain events are therefore assessed mainly by way of reportability. We now know of numerous brain events that are reportable, and comparable ones that are not. This fact invites experimental testing: why are we conscious of these words at this moment, while a few seconds later they have faded, but can still be called to mind? Why is activity in visual temporal lobe neurons reportable, while apparently similar activity in parietal regions is not? Why does the thalamocortical system support conscious experiences, while the comparably large cerebellum and basal ganglia do not? These are all testable questions.The empirical key is to treat consciousness as a controlled variable. We now know of cortical neurons that respond to conscious pictures presented to one eye, while competing unconscious pictures presented to the other eye evoke firing in closely related cells. Goodale and Milner have shown that visual control of manual reaching and grasping appears to be unconscious. Rees and colleagues have demonstrated that of two streams of visual information at the very centre of gaze, one can be conscious and the other not; the conscious one activates distinct brain areas, as assessed by fMRI. The competing unconscious visual stream, which surely reaches cortex, could not be detected. A rich literature has arisen comparing conscious and unconscious brain events in sleep and waking, anesthesia, epileptic states of absence, very specific damage to visual cortex, spared implicit function after brain damage, com...

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Replies to Commentaries

Cited by 2 publications

References 23 publications

Global Workspace Dynamics: Cortical “Binding and Propagation” Enables Conscious Contents

Global Workspace Dynamics: Cortical “Binding and Propagation” Enables Conscious Contents

Current concepts of consciousness with some implications for anesthesia

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