Abstract
BackgroundBiomarkers derived from neural activity of the brain present a vital tool for the prediction and evaluation of post-stroke motor recovery, as well as for real-time biofeedback opportunities.MethodsIn order to encapsulate recovery-related reorganization of brain networks into such biomarkers, we have utilized the generalized measure of association (GMA) and graph analyses, which include global and local efficiency, as well as hemispheric interdensity and intradensity. These methods were applied to electroencephalogram (EEG) data recorded during a study of 30 stroke survivors (21 male, mean age 57.9 years, mean stroke duration 22.4 months) undergoing 12 weeks of intensive therapeutic intervention.ResultsWe observed that decreases of the intradensity of the unaffected hemisphere are correlated (rs=−0.46;p<0.05) with functional recovery, as measured by the upper-extremity portion of the Fugl-Meyer Assessment (FMUE). In addition, high initial values of local efficiency predict greater improvement in FMUE (R2=0.16;p<0.05). In a subset of 17 subjects possessing lesions of the cerebral cortex, reductions of global and local efficiency, as well as the intradensity of the unaffected hemisphere are found to be associated with functional improvement (rs=−0.60,−0.66,−0.75;p<0.05). Within the same subgroup, high initial values of global and local efficiency, are predictive of improved recovery (R2=0.24,0.25;p<0.05). All significant findings were specific to the 12.5–25 Hz band.ConclusionsThese topological measures show promise for prognosis and evaluation of therapeutic outcomes, as well as potential application to BCI-enabled biofeedback.
Highlights
Biomarkers derived from neural activity of the brain present a vital tool for the prediction and evaluation of post-stroke motor recovery, as well as for real-time biofeedback opportunities
While the desire to condense intricate whole-brain graphs into scalar biomarkers naturally leads to the selection of large-scale metrics, we have examined intermediate and small-scale metrics, due to their specific applicability to the topic of stroke rehabilitation
Correlation between global/hemispheric measures and functional improvement In order to determine the utility of the global/hemispheric biomarkers for purposes of online biofeedback or evaluation of recovery, we calculated the correlation between their change over time and the change over time of the Fugl-Meyer upper extremity assessment (FMUE) functional measure
Summary
Biomarkers derived from neural activity of the brain present a vital tool for the prediction and evaluation of post-stroke motor recovery, as well as for real-time biofeedback opportunities. Plasticity of the human central nervous system (CNS) enables us to learn new information and acquire new cognitive or motor skills through structural and functional reorganization These changes can occur throughout life, and can be engaged after CNS trauma or disease in order to enhance or accelerate recovery [1, 2]. New therapeutic strategies employ brain-computer interfaces (BCI) to present biofeedback from the brain to the patient during training [8] This biofeedback informs the user whether a specific thought or action has produced the desired physiological response, rewarding specific patterns of brain activity and increasing the effectiveness of training. In this manner, perception-action coupling is expanded to include direct perception of neural activity. BCI-based therapies that utilize visual displays, functional electrical stimulation (FES), and robotic and orthotic devices to provide feedback to the user have been shown to be feasible and somewhat effective [7, 9,10,11,12,13,14,15,16,17,18,19,20,21,22]
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