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Abstract Stroke is a leading cause of adult disability worldwide, with approximately 101 million survivors globally. Over 60% of these individuals live with from long-term, often lifelong, movement impairments that significantly hinder their ability to perform essential daily activities and maintain independence. Post-stroke movement disabilities are highly associated with structural and functional changes in motor descending pathways, particularly the corticospinal tract (CST) and other indirect motor pathways via the brainstem. For decades, neuroengineers have been working to quantitively evaluate the post-stroke changes of motor descending pathways, aiming to establish a precision prognosis and tailoring treatments to post-stroke motor impairment. However, a clear and practicable technique has not yet been established as a breakthrough to change the standard of care for current clinical practice. In this review, we outline recent progress in neuroimaging, neuromodulation, and electrophysiological approaches for assessing structural and functional changes of motor descending pathways in stroke. We also discuss their limitations and challenges, arguing the need of artificial intelligence and large multi-modal data registry for a groundbreaking advance to this important topic. 

High-definition transcranial direct current stimulation (HD-tDCS) is a promising approach for stroke rehabilitation, which may induce functional changes in the cortical sensorimotor areas to facilitate movement recovery. However, it lacks an objective measure that can indicate the effect of HD-tDCS on alteration of brain activity. Quantitative electroencephalography (qEEG) has shown promising results as an indicator of post-stroke functional recovery. Therefore, this study aims to determine whether qEEG metrics could serve as quantitative measures to assess alteration in brain activity induced by HD-tDCS. Resting state EEG was collected from stroke participants before and after (1) anodal HD-tDCS of the lesioned hemisphere, (2) cathodal stimulation of the non-lesioned hemisphere, and (3) sham. The average power spectrum was calculated using the Fast Fourier Transform for frequency bands alpha, beta, delta, and theta. In addition, delta-alpha ratio (DAR), Delta-alpha-beta-theta ratio (DTABR), and directional brain symmetry index (BSI) were also evaluated. We found that both anodal and cathodal stimulation significantly decreased the DAR and BSI over various frequency bands, which are associated with reduced motor impairments and improved nerve conduction velocity from the brain to muscles. This result indicates that qEEG metrics DAR and BSI could be quantitative indicators to assess alteration of brain activity induced by HD-tDCS in stroke rehabilitation. This would allow future development of EEG-based neurofeedback system to guide and evaluate the effect of HD-tDCS on improving movement-related brain function in stroke.