Assessment of Event-Related EEG Power After Single-Pulse TMS in Unresponsive Wakefulness Syndrome and Minimally Conscious State Patients

In patients without a behavioral response, non-invasive techniques and new methods of data analysis can complement existing diagnostic tools by providing a method for detecting covert signs of residual cognitive function and awareness. The aim of this study was to investigate the brain oscillatory activities synchronized by single-pulse transcranial magnetic stimulation (TMS) delivered over the primary motor area in the time\u2013frequency domain in patients with the unresponsive wakefulness syndrome or in a minimally conscious state as compared to healthy controls. A time\u2013frequency analysis based on the wavelet transform was used to characterize rapid modifications of oscillatory EEG rhythms induced by TMS in patients as compared to healthy controls. The pattern of EEG changes in the patients differed from that of healthy controls. In the controls there was an early synchronization of slow waves immediately followed by a desynchronization of alpha and beta frequency bands over the frontal and centro-parietal electrodes, whereas an opposite early synchronization, particularly over motor areas for alpha and beta and over the frontal and parietal electrodes for beta power, was seen in the patients. In addition, no relevant modification in slow rhythms (delta and theta) after TMS was noted in patients. The clinical impact of these findings could be relevant in neurorehabilitation settings for increasing the awareness of these patients and defining new treatment procedures

Methods and models for brain connectivity assessment across levels of consciousness

The human brain is one of the most complex and fascinating systems in nature. In the last decades, two events have boosted the investigation of its functional and structural properties. Firstly, the emergence of novel noninvasive neuroimaging modalities, which helped improving the spatial and temporal resolution of the data collected from in vivo human brains. Secondly, the development of advanced mathematical tools in network science and graph theory, which has recently translated into modeling the human brain as a network, giving rise to the area of research so called Brain Connectivity or Connectomics. In brain network models, nodes correspond to gray-matter regions (based on functional or structural, atlas-based parcellations that constitute a partition), while links or edges correspond either to structural connections as modeled based on white matter fiber-tracts or to the functional coupling between brain regions by computing statistical dependencies between measured brain activity from different nodes. Indeed, the network approach for studying the brain has several advantages: 1) it eases the study of collective behaviors and interactions between regions; 2) allows to map and study quantitative properties of its anatomical pathways; 3) gives measures to quantify integration and segregation of information processes in the brain, and the flow (i.e. the interacting dynamics) between different cortical and sub-cortical regions. The main contribution of my PhD work was indeed to develop and implement new models and methods for brain connectivity assessment in the human brain, having as primary application the analysis of neuroimaging data coming from subjects at different levels of consciousness. I have here applied these methods to investigate changes in levels of consciousness, from normal wakefulness (healthy human brains) or drug-induced unconsciousness (i.e. anesthesia) to pathological (i.e. patients with disorders of consciousness)

Functional Magnetic Resonance Imaging

"Functional Magnetic Resonance Imaging - Advanced Neuroimaging Applications" is a concise book on applied methods of fMRI used in assessment of cognitive functions in brain and neuropsychological evaluation using motor-sensory activities, language, orthographic disabilities in children. The book will serve the purpose of applied neuropsychological evaluation methods in neuropsychological research projects, as well as relatively experienced psychologists and neuroscientists. Chapters are arranged in the order of basic concepts of fMRI and physiological basis of fMRI after event-related stimulus in first two chapters followed by new concepts of fMRI applied in constraint-induced movement therapy; reliability analysis; refractory SMA epilepsy; consciousness states; rule-guided behavioral analysis; orthographic frequency neighbor analysis for phonological activation; and quantitative multimodal spectroscopic fMRI to evaluate different neuropsychological states

Neuronal and behavioural pain processing

In our study “Neuronal and Behavioural Pain Processing: A Comparison Between a Strong Brand and a Generic Medication Placebo using the Example of Aspirin vs. 1A Pharma”, we investigated the expectation effects associated with brands by labelling two different placebo interventions. We tested the hypothesis, whether a strong brand can influence the impact of an inert substance. We studied the potential differences between the two placebos on a behavioural and neural level inducing the stimulus with noxious heat pain using Medoc. The research objective was to unveil, whether recipients can be influenced through expectations, verbal suggestions and the brand itself. We applied a two by two design with two identical placebo interventions that differed in their labelling. One group was told that they will receive 500 mg of “Aspirin” (original brand), while the other group was told that they will receive a popular ASA generic (“1A Pharma”). At the beginning, we established the individual pain levels of each subject with the numeric rating scale. Then we measured pain intensities before and after the intervention. The intervention was the administration of the placebo. We investigated behavioural as well as neural differences and looked for corresponding activated brain regions using functional magnetic resonance imaging (fMRI). Those participants, who were administered the original brand in the placebo intervention, showed a decrease in pain intensity. The generic group did not show any significant pain decrease. At the neuronal level, during the native condition, we observed activations of the anterior insula in both groups. After the intervention, the participants showed activations of the dorsomedial prefrontal cortex. The direct comparison of the two placebo conditions – the branded placebo vs. the generic – showed higher activations for the bilateral dorsolateral and dorsomedial prefrontal cortex. During the anticipation phase we observed activations of hippocampal, parahippocampal and adjacent brain areas for the generic group, only. These results suggest that only the original brand appears to evoke a behavioural response measured in terms of pain reduction. On a neuronal level, the activations were significant for the original brand only. Comparing the two placebo interventions, expectations seem to be significantly enhanced by the trusted brand, which appears to boost the placebo effect. Our results suggest that the underlying neural mechanisms of this placebo response are based on fronto-cortical neural networks

Vestibular System: Anatomy, Physiology, and Clinical Evaluation

Аbstract Studies on vestibular system have brought new experimental studies, clinical examinations, and the development of effective treatment for a number of diseases of this system. In particular, vestibular paroxysmal positional disorders of peripheral and central origin have been studied. The main criteria for differential diagnosis of these disorders have been determined. Vestibular dysfunction in canalolithiasis and cupololithiasis has been investigated clinically and histologically. Effective therapeutic and prophylactic positional maneuvers of three types have been introduced into clinical practice. They were developed taking into account the anatomical and physiological features of the vestibular system. Currently only 20% of vestibular reactions, in particular, using electronystagmography test (ENG), are estimated in the horizontal plane. Videonystagmography (VNG) gives the possibility of video recording of nystagmus in the directions of semicircular channels (vertical, diagonal, horizontal). The vestibular evoked myogenic potential test (VEMP) is being widely used in clinical practice. Magnetic coils and scanning laser ophthalmoscopes are gaining increasing significance in examining patients. A brief information on vestibular disorders after the Chornobyl nuclear power plant accident is also given

Investigation of the neuro-electrostimulation mechanisms by means of the functional MRI: Case study

The article overviewed contemporary neuromodulation approaches and challenges. The importance of the neurostimulation techniques was justified. The SYMPATHOCOR-01 neuro-electrostimulation device characterization was presented. The case study of the neuro-electrostimulation mechanisms by means of the neuroimaging was described. Case study consisted of 3 phases: imaging prior to the neuro-electrostimulation procedure, imaging right after the neuro-electrostimulation procedure and imaging after a 5-day stimulation course. Results of the functional magnetic resonance imaging revealed improvement of the functional connectivity strength in several brain regions as well as normalization of default mode network activity. Copyright © 2018 by SCITEPRESS – Science and Technology Publications, Lda. All rights reserved.The work was supported by Act 211 Government of the Russian Federation, contract № 02.A03.21.0006. The authors thank Ivan Brak, Elena Filimonova and Eugenia Kobeleva for participation in the data processing

The prognostic value of magnetic resonance imaging in moderate and severe traumatic brain injury : a Systematic Review and Meta-Analysis

Les traumatismes craniocérébraux constituent une cause importante de mortalité et de morbidité à travers le monde, et représentent un fardeau socioéconomique important dans les pays développés en raison de l'incapacité résiduelle post-traumatique dont souffrent les patients après leur traumatisme. Malgré la fréquence élevée d'issues cliniques défavorables à long terme, il existe actuellement peu d'indicateurs pronostiques permettant de guider le clinicien dans la prise en charge aiguë de ces patients et de conseiller leurs familles et proches. Plus de quatre décennies d'études observationnelles ont examiné l'utilisation de l'imagerie par résonance magnétique effectuée en phase aiguë dans son rôle potentiel à distinguer rapidement l'issue clinique post-traumatisme à long terme chez ces patients. Le présent travail vise donc à déterminer la valeur pronostique de l'imagerie par résonance magnétique effectuée en phase aiguë de traitement suite à un traumatisme craniocérébral modéré ou grave chez l'adulte, en utilisant une méthodologie de revue systématique et méta-analyse pronostique, afin d'identifier toutes les études évaluant la relation entre les modèles de lésions identifiés par résonance magnétique et l'issue clinique à long terme. Nos travaux ont identifié 58 études individuelles. Après méta-analyse, les lésions localisées dans le tronc cérébral se sont révélées être associées à une mortalité augmentée (toutes causes confondues) et une issue neurologique défavorable alors que les lésions compatibles avec une lésion axonale diffuse ont été associées à une augmentation du risque d'issue neurologique défavorable. Deux échelles de classement basées sur la gravité de la lésion ont été associées à des issues neurologiques de plus en plus défavorables au fur et à mesure de l'augmentation du nombre de structures cérébrales caudales touchées, confirmant ainsi l'importance des lésions profondes. Ces résultats démontrent l'utilité pronostique de l'imagerie par résonance magnétique effectuée rapidement après un traumatisme craniocérébral et indiquent la nécessité d'entreprendre des études pronostiques de cohorte de haute qualité et bien contrôlées, en raison du risque élevé de biais dans la littérature actuelle.Traumatic brain injury is a major cause of mortality and morbidity worldwide and represents a significant socioeconomic burden in developed nations due to residual post-trauma disability among survivors. Despite high rates of long-term unfavourable outcome, few prognostic indicators currently exist to guide early clinical management and counsel family and friends of patients. Over four decades of observational studies have examined the potential role of early magnetic resonance imaging of the brain to distinguish long-term clinical outcome by examining lesion patterns identifiable soon after trauma. This present work thus aims to determine the prognostic value of early magnetic resonance imaging following moderate or severe traumatic brain injury in adults by employing prognostic systematic review and meta-analysis methodology to identify all published studies assessing the relationship between magnetic resonance lesion patterns and long-term clinical outcome. Our search identified 58 individual studies; following meta-analysis, lesions located in the brainstem were associated with all-cause mortality and unfavourable neurological outcome while shear injury patterns compatible with diffuse axonal injury anywhere in the brain were associated with increased risk of unfavourable neurological outcome. Two scoring systems based on lesion depth were associated with progressively worse neurological outcomes as more caudal cerebral structures were affected, confirming the importance of deep lesions. These findings demonstrate the prognostic utility of magnetic resonance imaging early following traumatic brain injury and indicate the need for high quality, well-controlled, prognostic cohort studies given the elevated risk of bias in the current body of literature