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| The internal network of patients with brain death, coma, vegetative state (VS), minimally conscious state (MCS), and Locked-in syndrome (LIS). The network was extracted with ICA. The black and white contour represents a template of the internal network extracted from 11
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Recent studies in patients with disorders of consciousness (DOC) tend to support the view that awareness is not related to activity in a single brain region but to thalamo-cortical connectivity in the frontoparietal network. Functional neuroimaging studies have shown preserved albeit disconnected low-level cortical activation in response to externa...
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... psychophysiological interaction analyses of noxious processing revealed preserved modulation between primary somatosensory cortex and a large set of associative areas, again including fron- toparietal associative areas, in patients in minimally conscious state unresponsive state ( Laureys et al., 1999). More recently, fMRI stud- ies on the default/internal network confirmed a decreased cortico- cortical connectivity in patients with DOC (Boly et al., 2009;Cauda et al., 2009;Vanhaudenhuyse et al., 2010b) and an absence of con- nectivity in brain death (Boly et al., 2009) (Figure 2). Paralleling clinical experience, a non-linear correlation was found between this default/"internal" network connectivity and the level of con- sciousness ranging from healthy volunteers and pseudocoma/ locked-in syndrome, to minimally conscious, vegetative/unre- sponsive, and comatose patients ( Vanhaudenhuyse et al., 2010b). ...
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Background
Treatments aimed at hastening recovery from disorders of consciousness (DOC; e.g., coma, the vegetative state) have lagged behind a rapidly advancing science of these conditions. In part, this is due to the difficulty in selectively targeting the many deep regions of the brain known to be key for recovery from DOC. The (re)emergence of l...
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Citations
... On the other hand, patients can suffer from chronic disorders of consciousness following brain injury; our limited understanding of this phenomenon is an obstacle to the identification of better treatment options, and prognosis remains poor. Converging evidence suggests that consciousness is supported by a dynamic repertoire of brain activity [2][3][4][5][6][7][8][9][10][11][12][13] . These discoveries raise the question of how the rich dynamics that support consciousness can arise from a fixed network of anatomical connections-the brain's structural connectome [14][15][16][17][18][19][20][21] . ...
A central question in neuroscience is how consciousness arises from the dynamic interplay of brain structure and function. Here we decompose functional MRI signals from pathological and pharmacologically-induced perturbations of consciousness into distributed patterns of structure-function dependence across scales: the harmonic modes of the human structural connectome. We show that structure-function coupling is a generalisable indicator of consciousness that is under bi-directional neuromodulatory control. We find increased structure-function coupling across scales during loss of consciousness, whether due to anaesthesia or brain injury, capable of discriminating between behaviourally indistinguishable sub-categories of brain-injured patients, tracking the presence of covert consciousness. The opposite harmonic signature characterises the altered state induced by LSD or ketamine, reflecting psychedelic-induced decoupling of brain function from structure and correlating with physiological and subjective scores. Overall, connectome harmonic decomposition reveals how neuromodulation and the network architecture of the human connectome jointly shape consciousness and distributed functional activation across scales. Connectome harmonic decomposition analysis reveals how neuromodulation and the network architecture of the human connectome jointly shape consciousness and distributed functional activation across scales.
... Both SPECT and fMRI detected a reduction in subcortical cerebral blood oxygen level-dependent signals in the frontoparietal region in patients with generalized epilepsy (Gotman et al., 2005;Bai et al., 2010). Similarly, individuals with other unconscious states, such as coma, anesthesia, and brain death, showed impaired functional integration of the resembled cortex (Noirhomme et al., 2010;Crone et al., 2013;Gruenbaum, Frontiers in Neuroinformatics frontiersin.org . /fninf. . ...
Temporal lobe epilepsy (TLE) is a chronic neurological disorder that is divided into two subtypes, complex partial seizures (CPS) and simple partial seizures (SPS), based on clinical phenotypes. Revealing differences among the functional networks of different types of TLE can lead to a better understanding of the symbology of epilepsy. Whereas Although most studies had focused on differences between epileptic patients and healthy controls, the neural mechanisms behind the differences in clinical representations of CPS and SPS were unclear. In the context of the era of precision, medicine makes precise classification of CPS and SPS, which is crucial. To address the above issues, we aimed to investigate the functional network differences between CPS and SPS by constructing support vector machine (SVM) models. They mainly include magnetoencephalography (MEG) data acquisition and processing, construction of functional connectivity matrix of the brain network, and the use of SVM to identify differences in the resting state functional connectivity (RSFC). The obtained results showed that classification was effective and accuracy could be up to 82.69% (training) and 81.37% (test). The differences in functional connectivity between CPS and SPS were smaller in temporal and insula. The differences between the two groups were concentrated in the parietal, occipital, frontal, and limbic systems. Loss of consciousness and behavioral disturbances in patients with CPS might be caused by abnormal functional connectivity in extratemporal regions produced by post-epileptic discharges. This study not only contributed to the understanding of the cognitive-behavioral comorbidity of epilepsy but also improved the accuracy of epilepsy classification.
... This study is driven by the following question: given a self-regulating system poised at criticality, how would changes in its network topology affect its dynamics? Topological changes have been observed in functional brain networks of individuals in diverse states of consciousness, such as induced by psychedelics or anesthetics, in sleep or in coma [27][28][29][30][31][32][33][34]. The critical properties of a network are strongly determined by its topology are drawn from a power-law degree distribution with exponent γ = 2.7 and connected via a regular intermodular network with (a) k inter = 3, (b) k inter = 10, and (c) k inter = 32 intermodular links per module. ...
... Previous work has demonstrated that structural heterogeneity and modularity-both features of human brain networks [53][54][55][56]-are sufficient conditions to enable a Griffiths phase [26]. Functional brain networks have been shown to change significantly in different states of awareness, such as sleep, coma, anesthesia, or under the influence of psychedelics [28,[32][33][34]48]. Studies indicate a neural correlate between brain network integration and consciousness states [29,30,[57][58][59], which can be quantified using topological network metrics such as the clustering coefficient, local and global efficiency and entropy [27,31,48]. ...
Criticality has been conjectured as an integral part of neuronal network dynamics. Operating at a critical threshold requires precise parameter tuning and a corresponding mechanism remains an open question. Recent studies have suggested that topological features observed in brain networks give rise to a Griffiths phase, leading to power-law scaling in brain activity dynamics and the operational benefits of criticality in an extended parameter region. Motivated by growing evidence of neural correlates of different states of consciousness, we investigate how topological changes affect the expression of a Griffiths phase.We analyze the activity decay in modular networks using a susceptible-infected-susceptible propagation model and find that we can control the extension of the Griffiths phase by altering intra- and intermodular connectivity. We find that by adjusting system parameters, we can counteract changes in critical behavior and maintain a stable critical region despite changes in network topology. Our results give insight into how structural network properties affect the emergence of a Griffiths phase and how its features are linked to established topological network metrics. We discuss how those findings could contribute to an understanding of the changes in functional brain networks.
... This hypothesis is supported by studies that show variations in statistical features of RSN in altered states of consciousness [41][42][43] and mental disorders such as autism [44] or schizophrenia [45]. On the other hand, RSN have also been detected in people subjected to deep sedation [46], sleep [47], coma [48], or even vegetative states [49]. This fact could, in principle, challenges the hypothesis of RSN as a signature of consciousness. ...
Understanding the relationship between structural and functional organization represents one of the most important challenges in neuroscience. An increasing amount of studies show that this organization can be better understood by considering the brain as an interactive complex network. This approach has inspired a large number of computational models that combine experimental data with numerical simulations of brain interactions. In this paper, we present a summary of a data-driven computational model of synchronization between distant cortical areas that share a large number of overlapping neighboring (anatomical) connections. Such connections are derived from in vivo measures of brain connectivity using diffusion-weighted magnetic resonance imaging and are additionally informed by the presence of significant resting-state functionally correlated links between the areas involved. The dynamical processes of brain regions are simulated by a combination of coupled oscillator systems and a hemodynamic response model. The coupled oscillatory systems are represented by the Kuramoto phase oscillators, thus modeling phase synchrony between regional activities. The focus of this modeling approach is to characterize topological properties of functional brain correlation related to synchronization of the regional neural activity. The proposed model is able to reproduce remote synchronization between brain regions reaching reasonable agreement with the experimental functional connectivities. We show that the best agreement between model and experimental data is reached for dynamical states that exhibit a balance of synchrony and variations in synchrony providing the integration of activity between distant brain regions.
... This suggests that patients who subsequently recover from comas have better preserved cortico-cortical connectivity, similar to the higher cortico-cortical connectivity in higher states of consciousness observed in patients with chronic disorders of consciousness 18,36 and healthy volunteers under sedation. 37,38 In our study, we could not identify significant connections between the cortex and subcortical regions despite the known role of thalamocortical and other cortical-subcortical connections in consciousness. We reason that this issue is because those connections tend to be weak in states of reduced consciousness, and the patients in our studies were indeed unconscious. ...
BACKGROUND AND PURPOSE: Early outcome prediction of postanoxic patients in a coma after cardiac arrest proves challenging. Current prognostication relies on multimodal testing, using clinical examination, electrophysiologic testing, biomarkers, and structural MR imaging. While this multimodal prognostication is accurate for predicting poor outcome (ie, death), it is not sensitive enough to identify good outcome (ie, consciousness recovery), thus leaving many patients with indeterminate prognosis. We specifically assessed whether resting-state fMRI provides prognostic information, notably in postanoxic patients in a coma with indeterminate prognosis early after cardiac arrest, specifically for good outcome.
MATERIALS AND METHODS: We used resting-state fMRI in a prospective study to compare whole-brain functional connectivity between patients with good and poor outcomes, implementing support vector machine learning. Then, we automatically predicted coma outcome using resting-state fMRI and also compared the prediction based on resting-state fMRI with the outcome prediction based on DWI.
RESULTS: Of 17 eligible patients who completed the study procedure (among 351 patients screened), 9 regained consciousness and 8 remained comatose. We found higher functional connectivity in patients recovering consciousness, with greater changes occurring within and between the occipitoparietal and temporofrontal regions. Coma outcome prognostication based on resting-state fMRI machine learning was very accurate, notably for identifying patients with good outcome (accuracy, 94.4%; area under the receiver operating curve, 0.94). Outcome predictors using resting-state fMRI performed significantly better (P < .05) than DWI (accuracy, 60.0%; area under the receiver operating curve, 0.63).
CONCLUSIONS: Indeterminate prognosis might lead to major clinical uncertainty and significant variations in life-sustaining treatments. Resting-state fMRI might bridge the gap left in early prognostication of postanoxic patients in a coma by identifying those with both good and poor outcomes.
... We found only a few published RS fMRI studies of trauma patients who experienced MCS with brain damage [23,24]. In those studies, no DMN activation was observed in the damaged parts of the brain. ...
Purpose:
The management of patients with disorders of consciousness (DOC) constitutes a challenge for clinicians.
Case report:
We present the case of a 66-year-old man who developed coma with subsequent DOC after a severe traumatic brain injury. Behavioural assessment constitutes the gold standard in the evaluation of patients with DOC. In the case presented herein the neuropsychological findings were ambiguous, and the patient underwent functional magnetic resonance imaging (fMRI) to determine whether he was in a vegetative state or minimally conscious state. Three paradigms: passive, active, and resting state fMRI were used to study the brain activity in our patient.
Conclusions:
fMRI provided reliable evidence of preserved minimal consciousness. The neuroimaging techniques used in our patient were vital for his further treatment.
... During wakefulness, thalamo-cortical activity is weakly synchronized (Gent, Bandarabadi, Herrera, & Adamantidis, 2018), which is a necessary but not sufficient condition to enable consciousness. For example, as aforementioned, wakefulness is present in UWS patients but cortico-cortical communication is severely impaired ( Noirhomme et al., 2010), interfering with the reportable "awareness" component of consciousness. Another required condition for consciousness is an efficient large-scale cortico-cortical communication that can support awareness through the activation of attentional fronto-parietal networks (Luckmann, Jacobs, & Sack, 2014;Ptak, Schnider, & Fellrath, 2017). ...
Identifying the physiological processes underlying the emergence and maintenance of consciousness is one of the most fundamental problems of neuroscience, with implications ranging from fundamental neuroscience to the treatment of patients with disorders of consciousness (DOCs). One major challenge is to understand how cortical circuits at drastically different spatial scales, from local networks to brain-scale networks, operate in concert to enable consciousness, and how those processes are impaired in DOC patients. In this review, we attempt to relate available neurophysiological and clinical data with existing theoretical models of consciousness, while linking the micro- and macrocircuit levels. First, we address the relationships between awareness and wakefulness on the one hand, and cortico-cortical and thalamo-cortical connectivity on the other hand. Second, we discuss the role of three main types of GABAergic interneurons in specific circuits
responsible for the dynamical reorganization of functional networks. Third, we explore advances in the functional role of nested oscillations for neural synchronization and communication, emphasizing the importance of the balance between local (high-frequency) and distant (low-frequency) activity for efficient information processing. The clinical implications of these theoretical considerations are presented. We propose that such cellular-scale mechanisms could extend current theories of consciousness.
... Of special interest for clinical studies, it has been widely shown that different RSNs become altered in different pathological conditions such as deficit of consciousness [26,27,28,29,30], schizophrenia [31,32], epilepsy [33], Alzheimer's Disease [34,35,36,37,38,39] and healthy aging [40]. As far as we know, what RSN is altered after MODS has not been yet addressed. ...
... Of special interest for clinical studies, it has been widely shown that different RSNs become altered in different pathological conditions such as deficit of consciousness [26,27,28,29,30], schizophrenia [31,32], epilepsy [33], Alzheimer's Disease [34,35,36,37,38,39] and healthy aging [40]. As far as we know, what RSN is altered after MODS has not been yet addressed. ...
... During wakefulness, thalamo-cortical activity is weakly synchronized (Gent et al., 2018), which is a necessary, but not sufficient condition to enable consciousness. For example, as aforementioned, wakefulness is present in UWS patients but cortico-cortical communication is severely impaired ( Noirhomme et al., 2010), interfering with the "awareness" component of consciousness. Another required condition for consciousness is an efficient large-scale cortico-cortical communication that can support awareness through the activation of attentional fronto-parietal networks ( Luckmann et al., 2014;Ptak et al., 2017). ...
Identifying the physiological processes underlying the emergence and maintenance of consciousness is one of the most fundamental problems of neuroscience, with implications ranging from fundamental neuroscience to the treatment of patients with disorders of consciousness (DOC). One major challenge is to understand how cortical circuits at drastically different spatial scales, from local networks to brain-scale networks, operate in concert to enable consciousness, and how those processes are impaired in DOC patients. In this review, we attempt to relate available neurophysiological and clinical data with existing theoretical models of consciousness, while linking the micro- and macro-circuit levels. First, we address the relationships between awareness and wakefulness on the one hand, and cortico-cortical, and thalamo-cortical connectivity on the other hand. Second, we discuss the role of three main types of GABAergic interneurons in specific circuits responsible for the dynamical re-organization of functional networks. Third, we explore advances in the functional role of nested oscillations for neural synchronization and communication, emphasizing the importance of the balance between local (high-frequency) and distant (low-frequency) activity for efficient information processing. The clinical implications of these theoretical considerations are presented. We propose that such cellular-scale mechanisms could extend current theories of consciousness.
