Electroencephalography Analysis And Neuromodulation Assessment In Disorders Of Consciousness

Patients after severe brain injuries would be disorders of consciousness(DOC).The patients with DOC cause great damage to their family and burden the society.Meanwhile,they pose serious challenge to the modern clinical diagnosis and treatment.Consciousness assessment and neural rehabilitation are always critical issue in the neuroscience and clinical medicine domain.High misdiagnoses ratio and lack of assessment for neural modulation severely prevent the DOC patients from clinical rehabilitation.Therefore,from the neural informatics perspective,the present paper applies electroencephalography(EEG)and transcranial magnetic stimulation-electroencephalography(TMS-EEG)to assess consciousness levels of DOC and to evaluate modulation effects of the brain interventions.This work explores characteristics from EEG and TMS-EEG to describe consciousness levels of patients.It measures brain responses to the invasive brain stimulation of spinal cord stimulation and the non-invasive brain stimulation of transcranial direct current stimulation and repetitive transcranial magnetic stimulation.We evaluate their effects,provide approach for parameters selection and explore the potential mechanism of these modulation on neural rehabilitation.This work mainly includes the following results:Closely relationships of coherence and bicoherence characteristics with consciousness levels of patients with DOC are found based on a bigger samples of resting-state EEG.Results show that bicoherence markedly correlates with the consciousness levels of patients and the correlations are consistent in all ethology subclasses.In addition,characteristic from bicoherence can predict follow-up recovery of the DOC patients.Therefore,bicoherence characteristics may be potential consciousness related indices and helpful in consciousness diagnosis for DOC patients.To develop an measurement for individual consciousness assessing,we develop the TMS-EEG technology.We propose a novel de-noising method and extract characteristics of brain responses to evaluate cortical responses and connectivity features of patients with DOC.Results show that TMS-EEG could detect cortical difference in patients of vegetative state who have similar clinical presentation.And the results are consistent with functional connectivity and functional network assessment.Therefore,the results show that the developed TMS-EEG technology may has great value for diagnosis of patients with DOC.Comparisons of EEG analysis between before and after stimulation indicate that spinal cord stimulation of 70 Hz has better effects to induce electrophysiological changes in brain with DOC than stimulations with other frequency.In addition,TMS-EEG results prove that the stimulation with 70 Hz could alter excitability and connectivity features in the brain of the DOC patients.It provides approach to select parameters of the stimulation in clinical application.Meanwhile,functional connectivity and complex network parameters are analysed to explore modulation pathway and the underlying mechanism of spinal cord stimulation.It provides theoretical foundation for clinical application of the stimulation in the rehabilitation of patients with DOC.Different reactivity of brain in transcranial direct current stimulation is found between patients of minimally conscious state and vegetative state.The stimulation could markedly change the functional connectivity in patients of minimally conscious state but induce less changes in brain of vegetative state.And the modulation induced changes of connectivity correlates with the clinical behavioural scores of the patients.Both patients of minimally conscious state and vegetative state have notable changes of TMS-EEG characteristics after brain modulation.However,the stimulation induces more widely cortical changes in patients of minimally conscious state and the changes in patients of vegetative state are mainly located in the targeted area.The results indicate that EEG and TMS-EEG might be appropriate measurement for improving clinical application of the neural modulation.Moreover,these results provide potential physiological evidence for the different clinical effects observed between the patients of minimally conscious state and vegetative state.We propose a neural modulation technology based on the repetitive transcranial magnetic stimulation.EEG and TMS-EEG are used to evaluate the effects of the stimulation on the brains with DOC.Comparison between before and after stimulation indicates that the stimulation could cause significant changes of functional connectivity,complex network features,cortical reactivity and effective connectivity in patients of minimally conscious state.Furthermore,a long lasting modulation of consecutive 20 days is proven effective for improving clinical behavioural scores of the patients especially of minimally conscious state.Results of TMS-EEG of the patient with distinct consciousness improvement show evidence that characteristics derived from TMS-EEG could reliably evaluate the effects of brain modulations.Therefore,the study provides an effective protocol of neural modulation and the corresponding evaluation methods.It promotes the theoretical and technological development of neural rehabilitation for DOC patients.