The emergence of integrated information, complexity, and \u27consciousness\u27 at criticality

© 2020 by the authors. Integrated Information Theory (IIT) posits that integrated information (F) represents the quantity of a conscious experience. Here, the generalized Ising model was used to calculate F as a function of temperature in toy models of fully connected neural networks. A Monte-Carlo simulation was run on 159 normalized, random, positively weighted networks analogous to small five-node excitatory neural network motifs. Integrated information generated by this sample of small Ising models was measured across model parameter spaces. It was observed that integrated information, as an order parameter, underwent a phase transition at the critical point in the model. This critical point was demarcated by the peak of the generalized susceptibility (or variance in configuration due to temperature) of integrated information. At this critical point, integrated information was maximally receptive and responsive to perturbations of its own states. The results of this study provide evidence that F can capture integrated information in an empirical dataset, and display critical behavior acting as an order parameter from the generalized Ising model

Heart Rate Variability as an indicator of nociceptive pain in disorders of consciousness?

Background: Heart rate variability (HRV) has been proposed as an indicator of nociceptive pain processing1 although its reliability as pain indicator remains under debate. The objective was to study the interest of an HRV complexity analysis2 method as an indicator of nociceptive pain processing in severely brain-injured patients with disorders of consciousness. Methods: Twenty-two patients (11 in minimally conscious state [MCS], 11 in a vegetative state/unresponsive wakefulness syndrome [VS/UWS]) and 14 healthy subjects [HS] were included in this study. We administered a non-noxious and a noxious stimulation while recording the electrocardiographic response was recorded before, during, and following non-noxious and noxious stimulation. The short-term Complexity Index (CIs) was calculated. Mann-Whitney and Wilcoxon’s test were used to investigate differences in CIs according to the level of consciousness (i.e., HS vs patients and VS/UWS vs MCS) and the three conditions (i.e., baseline, non-noxious, noxious). The correlation between the three conditions and the Coma Recovery Scale-Revised3 were investigated by Spearman’s correlations. Results :We observed higher CIs values in HS as compared with patients during baseline and following the noxious stimulation. We also found higher CIs values in MCS vs VS/UWS patients following the noxious condition and lower values in the noxious vs non-noxious condition solely for the VS/UWS group. A correlation was found between CIs in noxious condition and Coma Recovery Scale-Revised scores. Conclusion: our data suggest a less complex autonomic response to noxious stimuli in VS/UWS patients4. Such analysis may help to better understand sympathovagal response to potentially painful environmental stimulation in brain-injured patients

Diagnostic Developments in Differentiating Unresponsive Wakefulness Syndrome and the Minimally Conscious State

When treating patients with a disorder of consciousness (DOC), it is essential to obtain an accurate diagnosis as soon as possible to generate individualized treatment programs. However, accurately diagnosing patients with DOCs is challenging and prone to errors when differentiating patients in a Vegetative State/Unresponsive Wakefulness Syndrome (VS/UWS) from those in a Minimally Conscious State (MCS). Upwards of ~40% of patients with a DOC can be misdiagnosed when specifically designed behavioral scales are not employed or improperly administered. To improve diagnostic accuracy for these patients, several important neuroimaging and electrophysiological technologies have been proposed. These include Positron Emission Tomography (PET), functional Magnetic Resonance Imaging (fMRI), Electroencephalography (EEG), and Transcranial Magnetic Stimulation (TMS). Here, we review the different ways in which these techniques can improve diagnostic differentiation between VS/UWS and MCS patients. We do so by referring to studies that were conducted within the last 10 years, which were extracted from the PubMed database. In total, 55 studies met our criteria (clinical diagnoses of VS/UWS from MCS as made by PET, fMRI, EEG and TMS- EEG tools) and were included in this review. By summarizing the promising results achieved in understanding and diagnosing these conditions, we aim to emphasize the need for more such tools to be incorporated in standard clinical practice, as well as the importance of data sharing to incentivize the community to meet these goals

Circadian Rhythms and Measures of CNS/Autonomic Interaction

The physiological role and relevance of the mechanisms sustaining circadian rhythms have been acknowledged. Abnormalities of the circadian and/or sleep-wakefulness cycles can result in major metabolic disorders or behavioral/professional inadequacies and stand as independent risk factors for metabolic, psychiatric, and cerebrovascular disorders and early markers of disease. Neuroimaging and clinical evidence have documented functional interactions between autonomic (ANS) and CNS structures that are described by a concept model (Central Autonomic Network) based on the brain-heart two-way interplay. The circadian rhythms of autonomic function, ANS-mediated processes, and ANS/CNS interaction appear to be sources of variability adding to a variety of environmental factors, and may become crucial when considering the ANS major role in internal environment constancy and adaptation that are fundamental to homeostasis. The CNS/ANS interaction has not yet obtained full attention and systematic investigation remains overdue. © 2019 by the authors. Licensee MDPI, Basel, Switzerland.Peer reviewe

Advances in the neurorehabilitation of severe disorder of consciousness

Introduction. The paper describes the evolution of knowledge concerning severe brain  injury which determines the Vegetative State/Unresponsive Wakefulness Syndrome. Background. The term Vegetative State was proposed by Jennet and Plum in 1972. Later  on, the Intensive Care Units progresses increased the survival of these patients and, contemporary, decreased their characteristic conditions of cachexia and severe dystonia. In  1994, the disease was conceived as a disconnection syndrome of the hemispheres from the  brainstem, mainly due to a temporary or permanent deficit of the functions of the white  matter. From 2005 on, the psychophysiological parameters relative to an emotional consciousness, albeit submerged, were described. Since then, it has been recognized that the  brain of these patients was not only to be considered living but also working.Conclusion. The latest studies that have greatly improved the knowledge of the physi-opathology of this particular state of consciousness. These new insights have led to the  formation of a European Union Task Force, which has proposed in 2009 to change the  name  from  a  Vegetative  State  to  Unresponsive  Wakefulness  Syndrome,  outlining  the  character of syndrome and not that of state, as forms of even late recovery in consciousness levels have been observed and described. 

Care and Neurorehabilitation in the Disorder of Consciousness: A Model in Progress

The operational model and strategies developed at the Institute S. Anna-RAN to be applied in the care and neurorehabilitation of subjects with disorders of consciousness (DOC) are described. The institute units are sequentially organized to guarantee appropriate care and provide rehabilitation programs adapted to the patients’ clinical condition and individual’s needs at each phase of evolution during treatment in a fast turnover rate. Patients eligible of home care are monitored remotely. Transferring advanced technology to a stage of regular operation is the main mission. Responsiveness and the time windows characterized by better residual responsiveness are identified and the spontaneous/induced changes in the autonomic system functional state and biological parameters are monitored both in dedicated sessions and by means of an ambient intelligence platform acquiring large databases from traditional and innovative sensors and interfaced with knowledge management and knowledge discovery systems. Diagnosis of vegetative state/unresponsive wakefulness syndrome or minimal conscious state and early prognosis are in accordance with the current criteria. Over one thousand patients with DOC have been admitted and treated in the years 1998–2013. The model application has progressively shortened the time of hospitalization and reduced costs at unchanged quality of services

Measures of CNS-Autonomic Interaction and Responsiveness in Disorder of Consciousness

Neuroimaging studies have demonstrated functional interactions between autonomic (ANS) and brain (CNS) structures involved in higher brain functions, including attention and conscious processes. These interactions have been described by the Central Autonomic Network (CAN), a concept model based on the brain-heart two-way integrated interaction. Heart rate variability (HRV) measures proved reliable as non-invasive descriptors of the ANS-CNS function setup and are thought to reflect higher brain functions. Autonomic function, ANS-mediated responsiveness and the ANS-CNS interaction qualify as possible independent indicators for clinical functional assessment and prognosis in Disorders of Consciousness (DoC). HRV has proved helpful to investigate residual responsiveness in DoC and predict clinical recovery. Variability due to internal (e.g. homeostatic and circadian processes) and environmental factors remains a key independent variable and systematic research with this regard is warranted. The interest in bidirectional ANS-CNS interactions in a variety of physiopathological conditions is growing, however these interactions have not been extensively investigated in DoC. In this brief review we illustrate the potentiality of brain-heart investigation by means of HRV analysis in assessing patients with DoC. The authors’ opinion is that this easy, inexpensive and non-invasive approach may provide useful information in the clinical assessment of this challenging patient population

HRV and Rehabilitation in the Severe Disorders of Consciousness

The Heart Rate Variability (HRV) analysis represents a non-invasive and robust method to analyse the ANS sympatho-vagal balance. It was also correlated to behavioural response in MCS and UWS/VS patients and its decreasing variability was associated to the increasing of critical conditions in these patients. Extensive monitoring of the autonomic nervous system is advisable in the disorders of consciousness, and HRV techniques appear suitable of application in this field. HRV methodologies benefit from being non-invasive and with positive benefit/cost ratios, and measures are obtained at limited costs, labour, and accuracy of recording. Also if indirect, information on the ANS functional state or responsiveness can be obtained also in absence of the subject’s collaboration and when sophisticated experimental designs and data recording procedures are impracticable or difficult as is the case with the severe disorders of consciousness. The Central Autonomic Network, and the two way brain-Heart interaction model provides neuroscientists and clinicians with an independent approach to be used both in the understanding of the HRV descriptors of the autonomic–CNS interaction and supplementing clinical or neuroimaging observations. The current clinical criteria for diagnosis and prognosis of the disorders of consciousness based on neurological signs of responsiveness should be reconsidered. The criteria should include the variability of responsiveness over time, and multiple testing should be mandatory to reduce the risks of misclassification. The correlation with the functional state of the ANS should be regarded as an independent indicator for diagnosis and prognosis and taken into proper account; monitoring should be extensive and focus also on non-neuronal factors. Reclassification of some patients or classes of patients may prove appropriate if based on systematic investigation

Music, Disorders of Consciousness and heart/brain two-way interaction in severe brain injured patient

Activations to pleasant and unpleasant musical stimuli were observed within an extensive neuronal network and different brain structures, as well as in the processing of the syntactic and semantic aspects of the music. The complexity of musical sample was described by Formal Complexity and General Dynamics parameters defined by Imberty’s semiology studies. Studies evidenced a correlation between autonomic activity and emotion evoked by music listening in patients with Disorders of Consciousness (DoC). The measures of heart rate variability (HRV) are thought to indirectly reflect these activities and interaction. Integrative models equate HRV to autonomic nervous system outputs, with HRV reflecting affective, physiological, “cognitive,” and behavioural elements and homeostatic responses. HRV provides tools for the evaluation of responsiveness in DoC and it has proved reliable in physiological research in the absence of conscious behaviour. Studies results put in evidence how the internal structure of the music can change the autonomic response in patients with DoC. Further investigations are required to better comprehend how musical stimulation can modify the autonomic response in DoC patients, in order to administer the stimuli in a more effective way