Neural correlates of consciousness: progress and problems

Neural correlates of consciousness: progress and problems Koch Massimini Boly Tononi

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Neural correlates of consciousness: progress and problems 2016 Nature Reviews Neuroscience 10.1038/nrn.2016.22 koch2016-neural-correlates-of-consciousness koch2016-neural-correlates-of-consciousness.txt, the project's staged copy 8ef45c3ca22c3aa3c29a337504789e69a4ffa809 open-access neuroscience

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0 spans located by searching the stored text for the quote's exact words, allowing any whitespace between them existence Quotation withheld because this record is not cleared for redistribution. neural correlates of consciousness Quotation withheld because this record is not cleared for redistribution. review review Quotation withheld because this record is not cleared for redistribution. mechanisms Diffusely projecting brainstem, hypothalamic and basal forebrain populations depolarize thalamic and cortical neurons, and this depolarization enables consciousness indirectly by making effective interactions between cortical areas possible. Quotation withheld because this record is not cleared for redistribution. mechanisms Fronto-parietal activity co-varies with reported perception because report-based tasks recruit attention, expectation, self-monitoring, planning and reporting, which precede or follow the experience rather than constituting it. Quotation withheld because this record is not cleared for redistribution. mechanisms Brainstem reticular formation, paramedian thalamus and postero-medial cortex act as activating influences and cortical hubs, thereby enabling the interactions among the cortical areas that supply conscious content. Quotation withheld because this record is not cleared for redistribution. The review restricts itself to visual and auditory studies and does not cover other modalities or metacognition. what this limits: the modality coverage of the review: THIS REVIEW FOCUSES ON VISUAL AND AUDITORY STUDIES; FOR ACCOUNTS OF THE NCC FOR METACOGNITION, BODY, TACTILE AND OLFACTORY EXPERIENCES, SEE REFS Quotation withheld because this record is not cleared for redistribution. The authors state that the empirical NCC research programme has inherent limits. what this limits: the empirical programme as a route to the question: WE OUTLINE THE INHERENT LIMITS OF SUCH AN EMPIRICAL RESEARCH PROGRAMME Quotation withheld because this record is not cleared for redistribution. NCC evidence cannot settle whether consciousness is present in brain-damaged patients, infants, animals or machines. what this limits: every clinical, developmental, comparative and machine application: THE NCC BY THEMSELVES CAN PROVIDE LITTLE INFORMATION ABOUT CONSCIOUSNESS IN PATIENTS WITH SEVERE BRAIN DAMAGE, INFANTS, FETUSES, NON-HUMAN SPECIES OR INTELLIGENT MACHINES Quotation withheld because this record is not cleared for redistribution. The conclusion that V1 is not part of the content-specific NCC may not generalise to untested visual attributes. what this limits: the conclusion that V1 is outside the content-specific NCC: IT IS NOT KNOWN WHETHER THIS CONCLUSION APPLIES TO OTHER VISUAL ATTRIBUTES, SUCH AS PRECISE SPATIAL TOPOGRAPHY, LUMINOSITY AND DETAILED CONTOURS Quotation withheld because this record is not cleared for redistribution. The field's central definition is stated by its own authors to admit two interpretations. what this limits: any use of the NCC as a single construct: the authors define it as the minimum neuronal mechanisms jointly sufficient for any one specific conscious percept, and state that there are two possible interpretations of that definition Quotation withheld because this record is not cleared for redistribution. Two popular candidate markers are reported to have no predictive power. what this limits: any use of gamma activity or the P3b wave as a marker of consciousness: the authors state these two popular candidates have not shown any predictive power Quotation withheld because this record is not cleared for redistribution. Consciousness is stated to be possible without reliable behavioural responses, with the misclassification named. what this limits: any inference from absent behaviour to absent consciousness: the authors state consciousness can be present even without reliable behavioural responses, and that minimally conscious patients can be misclassified as vegetative Quotation withheld because this record is not cleared for redistribution. full NCC full NCC Quotation withheld because this record is not cleared for redistribution. contentspecific NCC contentspecific NCC Quotation withheld because this record is not cleared for redistribution. gamma activity gamma activity Quotation withheld because this record is not cleared for redistribution. P3b wave P3b wave Quotation withheld because this record is not cleared for redistribution. behavioural responses behavioural responses Quotation withheld because this record is not cleared for redistribution. consciousness consciousness Quotation withheld because this record is not cleared for redistribution. the NCC - ONE DEFINITION, TWO READINGS, FLAGGED BY ITS AUTHORS: the minimum neuronal mechanisms jointly sufficient for any one specific conscious percept, with the review stating there are two possible interpretations depending on whether the specific content or the state is meant; the definition does not determine its own referent Quotation withheld because this record is not cleared for redistribution. the full NCC - A UNION OVER A SET STILL BEING ENUMERATED: it is constituted by the union of all content-specific NCC, so the whole is complete exactly when the enumeration is, and the enumeration is the research programme itself Quotation withheld because this record is not cleared for redistribution. gamma activity and the P3b wave - CANDIDATE MARKERS WITHDRAWN: both were popular and neither has shown predictive power, so two named quantities that circulated as indices of consciousness are reported as failing the role Quotation withheld because this record is not cleared for redistribution. contradicts → the proposal that the P3b/global ignition of fronto-parietal cortex is a signature of consciousness (REF. 142) Quotation withheld because this record is not cleared for redistribution. contradicts → earlier proposals that gamma activity or synchrony, and the P3b event-related potential, are signatures of consciousness Quotation withheld because this record is not cleared for redistribution. contentspecific NCC —part-of→ full NCC contentspecific NCC full NCC strength of the relation: 1 Quotation withheld because this record is not cleared for redistribution. gamma activity —causes→ consciousness gamma activity consciousness direction on the measure: no-change · strength of the relation: 1 Quotation withheld because this record is not cleared for redistribution. P3b wave —causes→ consciousness P3b wave consciousness direction on the measure: no-change · strength of the relation: 1 Quotation withheld because this record is not cleared for redistribution. Both the full and the content-specific NCC sit in a restricted temporo-parieto-occipital posterior hot zone rather than in the wide fronto-parietal network that earlier work emphasised. Quotation withheld because this record is not cleared for redistribution. Paradigms in which participants make no overt report yield a narrower content-specific NCC that contains posterior cortical areas but excludes prefrontal cortex. Quotation withheld because this record is not cleared for redistribution. Gamma synchrony survives or grows during early NREM sleep, anaesthesia and seizures and accompanies unconscious emotional stimuli, so it occurs without consciousness. Quotation withheld because this record is not cleared for redistribution. The P3b is missing in most clearly conscious brain-damaged patients and detects minimally conscious patients very poorly, so it fails as a signature of consciousness. Quotation withheld because this record is not cleared for redistribution. Primary visual cortex V1 is not part of the content-specific NCC for any visual attribute tested so far. Quotation withheld because this record is not cleared for redistribution. Consciousness survives removal of prefrontal cortex: complete bilateral frontal lobectomy and large bilateral prefrontal resections leave it intact. Quotation withheld because this record is not cleared for redistribution. Cerebellar lesions have little effect on consciousness and its contents. Quotation withheld because this record is not cleared for redistribution. Local rather than global EEG activation, especially over the posterior hot zone, may be what matters for consciousness. Quotation withheld because this record is not cleared for redistribution. The perturbational complexity index is the first measure that tracks the level of consciousness across sleep stages, anaesthetics and disorders of consciousness and does so for individual participants. Quotation withheld because this record is not cleared for redistribution. No single brain area turns out to be necessary for being conscious, though areas of the posterior cortical hot zone are the best candidates for both full and content-specific NCC. Quotation withheld because this record is not cleared for redistribution. neural correlates of consciousness (NCC) neural correlates of consciousness (NCC) Quotation withheld because this record is not cleared for redistribution. content-specific NCC content-specific NCC Quotation withheld because this record is not cleared for redistribution. full NCC full NCC Quotation withheld because this record is not cleared for redistribution. background conditions for consciousness background conditions for consciousness Quotation withheld because this record is not cleared for redistribution. posterior cortical hot zone posterior cortical hot zone Quotation withheld because this record is not cleared for redistribution. no-report paradigm no-report paradigm Quotation withheld because this record is not cleared for redistribution. perturbational complexity index (PCI) perturbational complexity index (PCI) Quotation withheld because this record is not cleared for redistribution. neuronal avalanches neuronal avalanches Quotation withheld because this record is not cleared for redistribution. P3b P3b Quotation withheld because this record is not cleared for redistribution. 0.14 — sensitivity of the P3b for identifying minimally conscious patients Quotation withheld because this record is not cleared for redistribution. 40% — proportion of unresponsive, sedated and hypothermic coma patients in whom multivariate decoding still finds a P3b-like component Quotation withheld because this record is not cleared for redistribution. 143 — number of severely brain-injured patients with disorders of consciousness in the structural imaging study of thalamic atrophy Quotation withheld because this record is not cleared for redistribution. more than one-third — share of awakenings from NREM sleep after which participants report having been conscious, despite reduced neuromodulatory activity Quotation withheld because this record is not cleared for redistribution. >75 μV — amplitude threshold for the repeated EEG slow waves used to assess loss of consciousness in humans Quotation withheld because this record is not cleared for redistribution. 120– 140 ms — latency of cortical responses to visual stimuli attributed to a feedforward sweep from V1 to extrastriate and inferior temporal cortex Quotation withheld because this record is not cleared for redistribution. close to 1 million — number of nerve cells in a bee brain, cited when asking whether insects can be conscious Quotation withheld because this record is not cleared for redistribution.

The full text of this article is not redistributable, so it is not included here. The evidence sentences are withheld with it; the tag layer and its grounding status remain. The article itself is at https://doi.org/10.1038/nrn.2016.22.