scholarly journals Perturbations in dynamical models of whole-brain activity dissociate between the level and stability of consciousness

2021 ◽  
Vol 17 (7) ◽  
pp. e1009139
Author(s):  
Yonatan Sanz Perl ◽  
Carla Pallavicini ◽  
Ignacio Pérez Ipiña ◽  
Athena Demertzi ◽  
Vincent Bonhomme ◽  
...  
Keyword(s):  
Computational Models ◽  
Brain Activity ◽  
Relevant Information ◽  
Complete Characterization ◽  
Brain State ◽  
Whole Brain ◽  
Brain Injured ◽  
Level Of Consciousness ◽  
The Stability ◽  
Injured Patients

Consciousness transiently fades away during deep sleep, more stably under anesthesia, and sometimes permanently due to brain injury. The development of an index to quantify the level of consciousness across these different states is regarded as a key problem both in basic and clinical neuroscience. We argue that this problem is ill-defined since such an index would not exhaust all the relevant information about a given state of consciousness. While the level of consciousness can be taken to describe the actual brain state, a complete characterization should also include its potential behavior against external perturbations. We developed and analyzed whole-brain computational models to show that the stability of conscious states provides information complementary to their similarity to conscious wakefulness. Our work leads to a novel methodological framework to sort out different brain states by their stability and reversibility, and illustrates its usefulness to dissociate between physiological (sleep), pathological (brain-injured patients), and pharmacologically-induced (anesthesia) loss of consciousness.

scholarly journals Perturbations in dynamical models of whole-brain activity dissociate between the level and stability of consciousness

2020 ◽  
Author(s):  
Yonatan Sanz Perl ◽  
Carla Pallavicini ◽  
Ignacio Pérez Ipiña ◽  
Athena Demertzi ◽  
Vincent Bonhomme ◽  
...  
Keyword(s):  
Computational Models ◽  
Brain Activity ◽  
Relevant Information ◽  
Complete Characterization ◽  
Brain State ◽  
Whole Brain ◽  
Brain Injured ◽  
Level Of Consciousness ◽  
The Stability ◽  
Injured Patients

AbstractConsciousness transiently fades away during deep sleep, more stably under anesthesia, and sometimes permanently due to brain injury. The development of an index to quantify the level of consciousness across these different states is regarded as a key problem both in basic and clinical neuroscience. We argue that this problem is ill-defined since such an index would not exhaust all the relevant information about a given state of consciousness. While the level of consciousness can be taken to describe the actual brain state, a complete characterization should also include its potential behavior against external perturbations. We developed and analyzed whole-brain computational models to show that the stability of conscious states provides information complementary to their similarity to conscious wakefulness. Our work leads to a novel methodological framework to sort out different brain states by their stability and reversibility, and illustrates its usefulness to dissociate between physiological (sleep), pathological (brain-injured patients), and pharmacologically-induced (anesthesia) loss of consciousness.

scholarly journals Neurologic Assessment of the Neurocritical Care Patient

2021 ◽  
Vol 12 ◽  
Author(s):  
Shane Musick ◽  
Anthony Alberico
Keyword(s):  
Gold Standard ◽  
Acute Stress ◽  
Cerebral Metabolism ◽  
Relevant Information ◽  
Hemodynamic Instability ◽  
Rapid Onset ◽  
Cerebral Microdialysis ◽  
Propofol Infusion Syndrome ◽  
Brain Injured ◽  
Injured Patients

Sedation is a ubiquitous practice in ICUs and NCCUs. It has the benefit of reducing cerebral energy demands, but also precludes an accurate neurologic assessment. Because of this, sedation is intermittently stopped for the purposes of a neurologic assessment, which is termed a neurologic wake-up test (NWT). NWTs are considered to be the gold-standard in continued assessment of brain-injured patients under sedation. NWTs also produce an acute stress response that is accompanied by elevations in blood pressure, respiratory rate, heart rate, and ICP. Utilization of cerebral microdialysis and brain tissue oxygen monitoring in small cohorts of brain-injured patients suggests that this is not mirrored by alterations in cerebral metabolism, and seldom affects oxygenation. The hard contraindications for the NWT are preexisting intracranial hypertension, barbiturate treatment, status epilepticus, and hyperthermia. However, hemodynamic instability, sedative use for primary ICP control, and sedative use for severe agitation or respiratory distress are considered significant safety concerns. Despite ubiquitous recommendation, it is not clear if additional clinically relevant information is gleaned through its use, especially with the contemporaneous utilization of multimodality monitoring. Various monitoring modalities provide unique and pertinent information about neurologic function, however, their role in improving patient outcomes and guiding treatment plans has not been fully elucidated. There is a paucity of information pertaining to the optimal frequency of NWTs, and if it differs based on type of injury. Only one concrete recommendation was found in the literature, exemplifying the uncertainty surrounding its utility. The most common sedative used and recommended is propofol because of its rapid onset, short duration, and reduction of cerebral energy requirements. Dexmedetomidine may be employed to facilitate serial NWTs, and should always be used in the non-intubated patient or if propofol infusion syndrome (PRIS) develops. Midazolam is not recommended due to tissue accumulation and residual sedation confounding a reliable NWT. Thus, NWTs are well-tolerated in selected patients and remain recommended as the gold-standard for continued neuromonitoring. Predicated upon one expert panel, they should be performed at least one time per day. Propofol or dexmedetomidine are the main sedative choices, both enabling a rapid awakening and consistent NWT.

scholarly journals Cholinergic neuromodulation of inhibitory interneurons facilitates functional integration in whole-brain models

2020 ◽  
Author(s):  
Carlos Coronel-Oliveros ◽  
Rodrigo Cofré ◽  
Patricio Orio
Keyword(s):  
Computational Models ◽  
Functional Organization ◽  
Brain Activity ◽  
Functional Integration ◽  
Whole Brain ◽  
Inhibitory Circuits ◽  
Proposed Model ◽  
Inhibitory Feedback ◽  
Noradrenergic Modulation ◽  
The Brain

AbstractSegregation and integration are two fundamental principles of brain structural and functional organization. Neuroimaging studies have shown that the brain transits between different functionally segregated and integrated states, and neuromodulatory systems have been proposed as key to facilitate these transitions. Although computational models have reproduced the effect of neuromodulation at the whole-brain level, the role of local inhibitory circuits and their cholinergic modulation has not been studied. In this article, we consider a Jansen & Rit whole-brain model in a network interconnected using a human connectome, and study the influence of the cholinergic and noradrenergic neuromodulatory systems on the segregation/integration balance. In our model, a newly introduced local inhibitory feedback enables the integration of whole-brain activity, and its modulation interacts with the other neuromodulatory influences to facilitate the transit between different functional states. Moreover, the new proposed model is able to reproduce an inverted-U relationship between noradrenergic modulation and network integration. Our work proposes a new possible mechanism behind segregation and integration in the brain.

When thoughts become action: An fMRI paradigm to study volitional brain activity in non-communicative brain injured patients

NeuroImage ◽  
2007 ◽  
Vol 36 (3) ◽  
pp. 979-992 ◽  
Author(s):  
M. Boly ◽  
M.R. Coleman ◽  
M.H. Davis ◽  
A. Hampshire ◽  
D. Bor ◽  
...  
Keyword(s):  
Brain Activity ◽  
Brain Injured ◽  
Injured Patients

scholarly journals Characterizing pupil dynamics coupling to brain state fluctuation based on lateral hypothalamic activity

2021 ◽  
Author(s):  
Kengo Takahashi ◽  
Filip Sobczak ◽  
Patricia Pais-Roldán ◽  
Xin Yu
Keyword(s):  
Brain Activity ◽  
Field Potential ◽  
Neuronal Cell ◽  
Cell Types ◽  
State Regulation ◽  
Anterior Cingulate ◽  
Brain State ◽  
Dependent Manner ◽  
Whole Brain ◽  
Brain Fmri

AbstractPupil dynamics presents varied correlation features with brain activity under different vigilant levels. The modulation of brain state changes can arise from the lateral hypothalamus (LH), where diverse neuronal cell types contribute to arousal regulation in opposite directions via the anterior cingulate cortex (ACC). However, the relationship of the LH and pupil dynamics has seldom been investigated. Here, we performed local field potential (LFP) recordings at the LH and ACC, and the whole brain fMRI with simultaneous fiber photometry Ca2+ recording in the ACC, to evaluate their correlation with brain state-dependent pupil dynamics. Both LFP and functional MRI (fMRI) data showed opposite correlation features to pupil dynamics, demonstrating an LH activity-dependent manner. Our results demonstrate that the correlation of pupil dynamics with ACC LFP and whole-brain fMRI signals depends on LH activity, indicating a role of the latter in brain state regulation.

scholarly journals Data augmentation based on dynamical systems for the classification of brain states

2020 ◽  
Author(s):  
Yonatan Sanz Perl ◽  
Carla Pallavicini ◽  
Ignacio Perez Ipiña ◽  
Morten Kringelbach ◽  
Gustavo Deco ◽  
...  
Keyword(s):  
Computational Models ◽  
Data Augmentation ◽  
Machine Learning Algorithms ◽  
Sleep Cycle ◽  
Great Promise ◽  
Brain State ◽  
Computer Assisted ◽  
Whole Brain ◽  
Brain States

AbstractThe application of machine learning algorithms to neuroimaging data shows great promise for the classification of physiological and pathological brain states. However, classifiers trained on high dimensional data are prone to overfitting, especially for a low number of training samples. We describe the use of whole-brain computational models for data augmentation in brain state classification. Our low dimensional model is based on nonlinear oscillators coupled by the empirical SC of the brain. We use this model to enhance a dataset consisting of functional magnetic resonance imaging recordings acquired during all stages of the human wake-sleep cycle. After fitting the model to the average FC of each state, we show that the synthetic data generated by the model yields classification accuracies comparable to those obtained from the empirical data. We also show that models fitted to individual subjects generate surrogates with enough information to train classifiers that present significant transfer learning accuracy to the whole sample. Whole-brain computational modeling represents a useful tool to produce large synthetic datasets for data augmentation in the classification of certain brain states, with potential applications to computer-assisted diagnosis and prognosis of neuropsychiatric disorders.

Ethical and Clinical Considerations at the Intersection of Functional Neuroimaging and Disorders of Consciousness

2016 ◽  
Vol 25 (4) ◽  
pp. 613-622 ◽  
Author(s):  
ADRIAN C. BYRAM ◽  
GRACE LEE ◽  
ADRIAN M. OWEN ◽  
URS RIBARY ◽  
A. JON STOESSL ◽  
...  
Keyword(s):  
Functional Neuroimaging ◽  
Brain Activity ◽  
Basic Research ◽  
Legal Issues ◽  
Disorders Of Consciousness ◽  
Strategic Development ◽  
Brain Injured ◽  
Ethical And Legal Issues ◽  
Clinical Considerations ◽  
Injured Patients

Abstract:Recent neuroimaging research on disorders of consciousness provides direct evidence of covert consciousness otherwise not detected clinically in a subset of severely brain-injured patients. These findings have motivated strategic development of binary communication paradigms, from which researchers interpret voluntary modulations in brain activity to glean information about patients’ residual cognitive functions and emotions. The discovery of such responsiveness raises ethical and legal issues concerning the exercise of autonomy and capacity for decisionmaking on matters such as healthcare, involvement in research, and end of life. These advances have generated demands for access to the technology against a complex background of continued scientific advancement, questions about just allocation of healthcare resources, and unresolved legal issues. Interviews with professionals whose work is relevant to patients with disorders of consciousness reveal priorities concerning further basic research, legal and policy issues, and clinical considerations.

Sign in / Sign up

Export Citation Format

Share Document