Measuring consciousness in severely damaged brains

Measuring consciousness in severely damaged brains Gosseries Di Laureys Boly

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Measuring consciousness in severely damaged brains 2014 Annual Review of Neuroscience 10.1146/annurev-neuro-062012-170339 gosseries2014-measuring-consciousness-in-severel gosseries2014-measuring-consciousness-in-severel.txt, the project's staged copy 091a7e8a062928286d16fa7545693694ed6085ed 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 method Quotation withheld because this record is not cleared for redistribution. disorders 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 Consciousness arises from a system's capacity to integrate information, so that networks supporting it must strike an optimal balance between functional integration and differentiation Quotation withheld because this record is not cleared for redistribution. mechanisms Loss of consciousness occurs through a breakdown of cortical effective connectivity, so that a local perturbation can no longer propagate as a widespread differentiated causal interaction Quotation withheld because this record is not cleared for redistribution. mechanisms Preserved cortical backward (top-down) connections generate the larger long-latency evoked components seen in MCS relative to VS/UWS Quotation withheld because this record is not cleared for redistribution. The assessment is gated by behaviour, so absence of response is not proof of absence of consciousness. what this limits: any bedside diagnosis of unawareness: the authors state the assessment is intrinsically gated by behavioral responsiveness and that absence of observed purposeful behaviors cannot be taken as definitive proof of the absence of consciousness Quotation withheld because this record is not cleared for redistribution. The misdiagnosis rate is given together with the assessment method that produces it. what this limits: any quoted misdiagnosis rate for unawareness: up to 40% applies Quotation withheld because this record is not cleared for redistribution. A named patient group is misdiagnosed despite preserved awareness. what this limits: any diagnosis of a disorder of consciousness: locked-in syndrome patients can be misdiagnosed as DOC despite preserved awareness, because of complete paralysis of voluntary muscles except vertical eye movements Quotation withheld because this record is not cleared for redistribution. The neuroimaging paradigm's validity rests on a control study the authors say is still needed. what this limits: any use of an active-task neuroimaging paradigm as evidence of willful response: the authors state validation studies should be performed to ensure passive listening cannot elicit a similar brain activity pattern Quotation withheld because this record is not cleared for redistribution. the normalized Lempel-Ziv complexity measure, originally defined for finite symbol sequences, is computed on TMS-evoked EEG spatiotemporal response maps to yield the perturbational complexity index Quotation withheld because this record is not cleared for redistribution. a separate experiment run on the same task eliminates: reflexive activation as the source of the response, and so establishes the task's specificity to conscious responses · outcome (stated by the tagger, no quotation): held Quotation withheld because this record is not cleared for redistribution. comparing active against passive conditions, and runs attending to the patient's own name against runs attending to another name eliminates: a nonreflexive response being mistaken for command-following, and a nonspecific response being mistaken for a targeted one · outcome (stated by the tagger, no quotation): held Quotation withheld because this record is not cleared for redistribution. instructing subjects NOT to perform the task and recording what happens eliminates: activation that would have occurred without any intention to comply - the response is absent when compliance is withheld · outcome (stated by the tagger, no quotation): held Quotation withheld because this record is not cleared for redistribution. behavioral responsiveness behavioral responsiveness Quotation withheld because this record is not cleared for redistribution. purposeful behaviors purposeful behaviors Quotation withheld because this record is not cleared for redistribution. Misdiagnosis of unawareness Misdiagnosis of unawareness Quotation withheld because this record is not cleared for redistribution. clinical consensus clinical consensus Quotation withheld because this record is not cleared for redistribution. locked-in syndrome locked-in syndrome Quotation withheld because this record is not cleared for redistribution. bedside consciousness - WHAT THE PATIENT CAN SHOW, NOT WHAT THEY HAVE: the assessment is intrinsically gated by behavioral responsiveness, and the same reading is returned by a patient who is unconscious and by one who is conscious and unable to demonstrate it, which the review states cannot be treated as proof either way Quotation withheld because this record is not cleared for redistribution. the 40% misdiagnosis rate - CONDITIONAL ON THE INSTRUMENT: it applies to diagnosis based solely on clinical consensus without appropriate behavioral scales, so the number measures a practice rather than a difficulty, and the practice is nameable and fixable Quotation withheld because this record is not cleared for redistribution. the active-task paradigm - VALID ONLY IF A CONTROL HOLDS THAT HAS NOT BEEN RUN: its status as evidence of willful response depends on passive listening not producing a similar pattern, and the authors say validation studies should be performed to establish that Quotation withheld because this record is not cleared for redistribution. qualifies → Ferreira (2007), Manning (2012) differs in: WHO IS APPLYING THE CATEGORY. The law is stated as turning on the label - 'the right of the medical team to withdraw artificial nutrition and hydration from patients in VS/UWS, but not those in MCS' - and then: 'Opinions on these end-of-life decisions vary, however, depending not only on the diagnosis of the patient, Quotation withheld'. So the same category, on the same patient, does not determine the same decision Quotation withheld because this record is not cleared for redistribution. contradicts → the assumption that locked-in patients have poor quality of life differs in: WHO IS ASKED. The quality-of-life question 'is difficult to address in the absence of communication with the patient' - and where communication IS possible the answer inverts: 'it is striking to note, however, that Quotation withheld'. The inference drawn from outside about a state is contradicted by the only group in that state who can answer Quotation withheld because this record is not cleared for redistribution. builds-on → Schnakers et al. (2009) differs in: WHICH INSTRUMENT PRODUCED THE DIAGNOSIS. The 40% figure is not a property of the patients: misdiagnosis is that frequent 'Quotation withheld', and the review names the scale that does better in the next sentence. Quoted without its condition, the number describes the population rather than the procedure Quotation withheld because this record is not cleared for redistribution. clinical consensus —causes→ Misdiagnosis of unawareness clinical consensus Misdiagnosis of unawareness holds when: when diagnosis rests on clinical consensus alone, without · direction on the measure: increases · strength of the relation: 1 Quotation withheld because this record is not cleared for redistribution. Unawareness is misdiagnosed in up to 40% of cases when clinicians rely on consensus impression instead of a standardised behavioural scale. Quotation withheld because this record is not cleared for redistribution. Only about one in five patients with disorders of consciousness produces a positive response on active command-following neuroimaging paradigms. Quotation withheld because this record is not cleared for redistribution. A negative result on an active paradigm can never exclude that the patient retains awareness. Quotation withheld because this record is not cleared for redistribution. The perturbational complexity index separates conscious from unconscious states across subjects and conditions, staying above 0.31 in wakefulness, MCS, EMCS, LIS and REM sleep and below 0.31 in NREM sleep, vegetative state and anaesthesia. Quotation withheld because this record is not cleared for redistribution. No conventional neuroimaging technique on its own is adequate to diagnose consciousness in a brain-damaged patient. Quotation withheld because this record is not cleared for redistribution. Preserved PET metabolism cannot serve as proof of consciousness, since metabolism can be normal or raised during epileptic seizures in which the subject is unconscious. Quotation withheld because this record is not cleared for redistribution. In NREM sleep, midazolam anaesthesia and vegetative state, TMS triggers a stereotypical local slow wave, indicating a breakdown of effective connectivity. Quotation withheld because this record is not cleared for redistribution. Neuroimaging and electrophysiology show consistent group differences between MCS and VS/UWS patients. Quotation withheld because this record is not cleared for redistribution. About 20% of VS/UWS patients show an atypical brain activity pattern. Quotation withheld because this record is not cleared for redistribution. The contents of consciousness in MCS remain inaccessible because these patients cannot give the reports on which content assessment normally depends. Quotation withheld because this record is not cleared for redistribution. unresponsive wakefulness syndrome unresponsive wakefulness syndrome Quotation withheld because this record is not cleared for redistribution. minimally conscious state (MCS) minimally conscious state (MCS) Quotation withheld because this record is not cleared for redistribution. disorders of consciousness (DOC) disorders of consciousness (DOC) Quotation withheld because this record is not cleared for redistribution. locked-in syndrome (LIS) locked-in syndrome (LIS) Quotation withheld because this record is not cleared for redistribution. active paradigm active paradigm Quotation withheld because this record is not cleared for redistribution. passive paradigm passive paradigm Quotation withheld because this record is not cleared for redistribution. Coma Recovery Scale-Revised (CRS-R) Coma Recovery Scale-Revised (CRS-R) Quotation withheld because this record is not cleared for redistribution. default mode network (DMN) default mode network (DMN) Quotation withheld because this record is not cleared for redistribution. coma coma 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. mismatch negativity (MMN) mismatch negativity (MMN) Quotation withheld because this record is not cleared for redistribution. transcranial magnetic stimulation (TMS) transcranial magnetic stimulation (TMS) Quotation withheld because this record is not cleared for redistribution. positron emission tomography (PET) positron emission tomography (PET) Quotation withheld because this record is not cleared for redistribution. up to 40% — rate of misdiagnosed unawareness when standardised behavioural scales are not used Quotation withheld because this record is not cleared for redistribution. about 20% — share of DOC patients who respond positively to active command-following paradigms Quotation withheld because this record is not cleared for redistribution. 0.31 — PCI threshold separating conscious from unconscious states Quotation withheld because this record is not cleared for redistribution. 0.44 and 0.67 / 0.12 and 0.31 — observed PCI ranges in wakefulness versus in NREM sleep and anaesthesia Quotation withheld because this record is not cleared for redistribution. about 20% — share of behaviourally vegetative patients showing an atypical brain activity pattern Quotation withheld because this record is not cleared for redistribution. 30 s — duration of each imagery block alternated with rest in the tennis imagery fMRI paradigm Quotation withheld because this record is not cleared for redistribution. 7 / 3 of 10 — authors' experience of how many bedside-diagnosed VS/UWS patients show the classical hypometabolic PET pattern versus preserved metabolism Quotation withheld because this record is not cleared for redistribution. >6 — CRS-R total score on admission that acts as a favourable prognostic factor Quotation withheld because this record is not cleared for redistribution. minimum 5 times — number of repeated CRS-R assessments the authors recommend before a final diagnosis Quotation withheld because this record is not cleared for redistribution.

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