Characteristics And Mechanism Analysis Of Multimodal Neuro-vascular Coupling For Rehabilitation Assessment In Stroke Patients

Stroke is a neurological disorder that results in damage to brain tissue due to the rupture or blockage of blood vessels,leading to impaired blood flow to the brain.Limb motor dysfunction after stroke is a serious threat to the living quality of patients and brings a heavy burden on individuals,families,and society.The development and implementation of effective rehabilitation strategies are crucial for patient recovery,relying on objective and comprehensive assessment techniques.The multimodal neuro-vascular coupling(MNVC)is a physiological phenomenon to reflect the multilayered characteristics of the information interaction among brain electrical activity,oxygen metabolism and the synergistic interaction between them.The research of the MNVC can contribute to reveal the brain functional status and the synergistic interactions and mechanisms between the nervous system and the blood circulation system,and provide a fresh perspective for quantitative assessment of the functional status of stroke patients.The content in this thesis mainly focused on the MNVC research in the neuro-vascular system.On basis of the theories of the dynamic signal processing such as information entropy and causal analysis methods were proposed to investigate the coupling characteristic of electroencephalography(EEG),functional near-infrared spectroscopy(f NIRS)signal and the synchronization characteristics between EEG and f NIRS signals from the linearity,nonlinearity,local frequency band,multiscale,and phase synchronization perspectives.During the multi-joint coordinated upper limb movement tasks involving shoulder,elbow,and wrist joints,multi-channel EEG and multi-channel f NIRS signals(including oxyhemoglobin(Hb O)and deoxyhemoglobin(Hb R)concentration signals)were simultaneously recorded from stroke patients and healthy subjects.Furthermore,the multi-level interaction characteristics,such as cortical functional coupling,cerebral hemodynamics and neurovascular coupling were analyzed from EEG and f NIRS signals.After that,the thesis delved into exploring the correlation and complementarity between the multi-level MNVC characteristics,and an analysis of the correlation between the multi-level characteristics of MNVC and clinical assessment scales was conducted to identify characteristics with noteworthy correlations.On this basis,a stroke rehabilitation status assessment model was constructed,integrating qualitative scales and quantitative indicators.This model can realize the visual presentation of the MNVC characteristics and provide a theoretical basis for the application of MNVC in the rehabilitation assessment of stroke patients.Above all,the innovative achievements in this study mainly contained the following aspects.(1)To investigate the nonlinear,local frequency band and multiscale characteristics of coupled oscillations in the cortical regions after stroke,novel causality methods,named wavelet packet decomposition-partial directed coherence(WPDPDC)and wavelet packet decomposition-multiscale transfer entropy(WPDMSTE),were proposed.From nonlinear and multi-scale perspectives,the WPDPDC and WPDMSTE methods were performed to analyze the local frequency band and frequency-scale characteristics of cortical functional coupling in both stroke patients and healthy subjects during the specific upper limb movement tasks.These studies provided a theoretical foundation for exploring changes in brain function and pathological mechanisms after stroke.(2)To analyze the changes of space-time characteristics of cerebral hemodynamics in the cerebral vessels after stroke,the multi-level characteristics,such as the coupling and the phase difference characteristics between Hb O and Hb R concentrations,and the linear synchronization and the phase synchronization characteristics of multi-channel Hb O/Hb R concentrations were expanded.From the perspective of linear synchronization and phase synchronization,the characteristics and mechanisms of cerebral hemodynamics were explored in stroke patients and healthy subjects under the specific upper limb movements.The above hemodynamic studies provided the feasibility of in-depth understanding of the mechanisms of oxygen metabolism and the remodeling mechanism of brain after stroke.(3)To explore the complex characteristics of neurovascular coupling after stroke,methods were employed to analyze the neurovascular coupling characteristics through the linear correlation between EEG and f NIRS signals and the brain activation patterns resulting from the modulation of f NIRS by EEG rhythm features.After that,these two methods were applied to investigate the synergistic interaction between the nervous system and the blood circulation system in stroke patients and healthy subjects under the specific upper limb movements.These studies provided a new perspective for the abnormal mechanism of neurovascular coupling and the reconstruction mechanism of motor function after stroke.(4)Based on the correlation analysis method,the correlation between the MNVC characteristics and the FMA-UE assessment scale for stroke patients,and the association relationships among the characteristics of cortical functional coupling,cerebral hemodynamics and neurovascular coupling were analyzed to construct a stroke rehabilitation status assessment model.This model,constructed by combining qualitative scale indicators with the quantitative MNVC characteristics,can realized the visual expression of multi-level MNVC characteristics.This research preliminarily verified the effectiveness of the MNVC in stroke rehabilitation assessment,and provided a feasible basis for the quantitative assessment of stroke patients.