Browsing by Author "Ray, Andreas M."
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Item Brain oscillatory activity as a biomarker of motor recovery in chronic stroke(2020-04-01) Ray, Andreas M.; Figueiredo, Thiago D. C.; López‐Larraz, Eduardo; Birbaumer, Niels; Ramos‐Murguialday, Ander; López-Larraz, Eduardo; Ramos-Murguialday, Ander; Medical TechnologiesIn the present work, we investigated the relationship of oscillatory sensorimotor brain activity to motor recovery. The neurophysiological data of 30 chronic stroke patients with severe upper‐limb paralysis are the basis of the observational study presented here. These patients underwent an intervention including movement training based on combined brain–machine interfaces and physiotherapy of several weeks recorded in a double‐blinded randomized clinical trial. We analyzed the alpha oscillations over the motor cortex of 22 of these patients employing multilevel linear predictive modeling. We identified a significant correlation between the evolution of the alpha desynchronization during rehabilitative intervention and clinical improvement. Moreover, we observed that the initial alpha desynchronization conditions its modulation during intervention: Patients showing a strong alpha desynchronization at the beginning of the training improved if they increased their alpha desynchronization. Patients showing a small alpha desynchronization at initial training stages improved if they decreased it further on both hemispheres. In all patients, a progressive shift of desynchronization toward the ipsilesional hemisphere correlates significantly with clinical improvement regardless of lesion location. The results indicate that initial alpha desynchronization might be key for stratification of patients undergoing BMI interventions and that its interhemispheric balance plays an important role in motor recovery.Item Electromyographic indices of muscle fatigue of a severely paralyzed chronic stroke patient undergoing upper limb motor rehabilitation(IEEE Computer Society, 2019-05-16) Ray, Andreas M.; Maillot, Aurélien; Helmhold, Florian; Mahmoud, Wala Jaser; López-Larraz, Eduardo; Ramos-Murguialday, Ander; Medical TechnologiesModern approaches to motor rehabilitation of severe upper limb paralysis in chronic stroke decode movements from electromyography for controlling rehabilitation orthoses. Muscle fatigue is a phenomenon that influences these neurophysiological signals and may diminish the decoding quality. Characterization of these potential signal changes during movement patterns of rehabilitation training could therefore help improve the decoding accuracy. In the present work we investigated how electromyographic indices of muscle fatigue in the Deltoid Anterior muscle evolve during typical forward reaching movements of a rehabilitation training in healthy subjects and a stroke patient. We found that muscle fatigue in healthy subjects changed the neurophysiological signal. In the patient, however, no consistent change was observed over several sessions.Item Movement-related brain oscillations vary with lesion location in severely paralyzed chronic stroke patients(Institute of Electrical and Electronics Engineers Inc., 2017-09-13) Ray, Andreas M.; Lopez-Larraz, Eduardo; Figueiredo, Thiago C.; Birbaumer, Niels; Ramos-Murguialday, Ander; Medical TechnologiesIn the past few years, innovative upper-limb rehabilitation methods have been proposed for chronic stroke patients. These methods aim at functional motor rehabilitation using Brain-machine interfaces to constitute an alternate pathway from the brain to the muscles. Even in patients with absence of residual finger movements, recovery could be achieved. The extent to which these interventions are affected by individual lesion topology is yet to be understood. In this study EEG was measured in 30 chronic stroke patients during movement attempts of the paretic arm. We show that the magnitude of the event-related desynchronization was smaller in patients presenting lesions with involvement of the motor cortex. This could have important implications on the design of new rehabilitation schemes for these patients, which might benefit from carefully tailored interventions.Item Sensorimotor rhythm modulation depends on resting-state oscillations and cortex integrity in severely paralyzed stroke patients(IEEE Computer Society, 2019-05-16) López-Larraz, Eduardo; Ray, Andreas M.; Birbaumer, Niels; Ramos-Murguialday, Ander; Medical TechnologiesAlpha oscillatory activity and its dynamics have a key role in motor and sensory functions. Stroke affects different brain structures, which can result in pathological changes in alpha oscillations. We studied the relationship between the amplitude of alpha oscillations in resting state and their modulation during the attempt of movement in 37 patients with severe paralysis after stroke. As previously observed in healthy subjects, resting-state alpha activity significantly correlated with the alpha event-related desynchronization (ERD) during the attempt of movement of the paralyzed hand. Further, alpha ERD correlated with the presence or absence of damage in cortical structures, but resting-state alpha power did not. This result provides new insights on the understanding of the brain changes after stroke, which may help in future therapies to help the patients to recover their lost motor function.Item Stroke lesion location influences the decoding of movement intention from EEG(Institute of Electrical and Electronics Engineers Inc., 2017-09-13) Lopez-Larraz, Eduardo; Ray, Andreas M.; Figueiredo, Thiago C.; Bibian, Carlos; Birbaumer, Niels; Ramos-Murguialday, Ander; Medical TechnologiesRecent studies have demonstrated the efficacy of brain-machine interfaces (BMI) for motor rehabilitation after stroke, especially for those patients with severe paralysis. However, a cerebro-vascular accident can affect the brain in many different manners, and lesions in diverse areas, even from significantly different volumes, can lead to similar or equal motor deficits. The location of the insult influences the way the brain activates when moving or attempting to move a paralyzed limb. Since the essence of a rehabilitative BMI is to precisely decode motor commands from the brain, it is crucial to characterize how lesion location affects the measured signals and if and how it influences BMI performance. This paper compares the performances of an electroencephalography (EEG)-based movement intention decoder in two groups of severely paralyzed chronic stroke patients: 14 with subcortical lesions and 14 with mixed (i.e., cortical and subcortical) lesions. We show that the lesion location influences the performance of the BMI when decoding the movement attempts of the paretic arm. The obtained results underline the need for further developments for a better individualization of BMI-based rehabilitative therapies for stroke patients.