1,422 research outputs found
Rehabilitation Induced Neural Plasticity after Acquired Brain Injury
No full textNeural Plasticity is an interdisciplinary journal dedicated to the publication of articles related to all aspects of neural plasticity, with special emphasis on its functional significance as reflected in behavior and in psychopathology
Decomposing time series data by a non-negative matrix factorization algorithm with temporally constrained coefficients
No full textThe non-negative matrix factorization algorithm (NMF) decomposes a data matrix into a set of non-negative basis vectors, each scaled by a coefficient. In its original formulation, the NMF assumes the data samples and dimensions to be independently distributed, making it a lessthan-ideal algorithm for the analysis of time series data with temporal correlations. Here, we seek to derive an NMF that accounts for temporal dependencies in the data by explicitly incorporating a very simple temporal constraint for the coefficients into the NMF update rules. We applied the modified algorithm to 2 multi-dimensional electromyographic data sets collected from the human upper-limb to identify muscle synergies. We found that because it reduced the number of free parameters in the model, our modified NMF made it possible to use the Akaike Information Criterion to objectively identify a model order (i.e., the number of muscle synergies composing the data) that is more functionally interpretable, and closer to the numbers previously determined using ad hoc measures
Stability of muscle synergies for voluntary actions after cortical stroke in humans
No full textProduction of voluntary movements relies critically on the functional integration of several motor cortical areas, such as the primary motor cortex, and the spinal circuitries. Surprisingly, after almost 40 years of research, how the motor cortices specify descending neural signals destined for the downstream interneurons and motoneurons has remained elusive. In light of the many recent experimental demonstrations that the motor system may coordinate muscle activations through a linear combination of muscle synergies, we hypothesize that the motor cortices may function to select and activate fixed muscle synergies specified by the spinal or brainstem networks. To test this hypothesis, we recorded electromyograms (EMGs) from 12–16 upper arm and shoulder muscles from both the unaffected and the stroke-affected arms of stroke patients having moderate-to-severe unilateral ischemic lesions in the frontal motor cortical areas. Analyses of EMGs using a nonnegative matrix factorization algorithm revealed that in seven of eight patients the muscular compositions of the synergies for both the unaffected and the affected arms were strikingly similar to each other despite differences in motor performance between the arms, and differences in cerebral lesion sizes and locations between patients. This robustness of muscle synergies that we observed supports the notion that descending cortical signals represent neuronal drives that select, activate, and flexibly combine muscle synergies specified by networks in the spinal cord and/or brainstem. Our conclusion also suggests an approach to stroke rehabilitation by focusing on those synergies with altered activations after stroke
Muscle synergy patterns as physiological markers of motor cortical damage
No full textThe experimental findings herein reported are aimed at gaining a perspective on the complex neural events that follow lesions of the motor cortical areas. Cortical damage, whether by trauma or stroke, interferes with the flow of descending signals to the modular interneuronal structures of the spinal cord. These spinal modules subserve normal motor behaviors by activating groups of muscles as individual units (muscle synergies). Damage to the motor cortical areas disrupts the orchestration of the modules, resulting in abnormal movements. To gain insights into this complex process, we recorded myoelectric signals from multiple upper-limb muscles in subjects with cortical lesions. We used a factorization algorithm to identify the muscle synergies. Our factorization analysis revealed, in a quantitative way, three distinct patterns of muscle coordination—including preservation, merging, and fractionation of muscle synergies—that reflect the multiple neural responses that occur after cortical damage. These patterns varied as a function of both the severity of functional impairment and the temporal distance from stroke onset. We think these muscle-synergy patterns can be used as physiological markers of the status of any patient with stroke or trauma, thereby guiding the development of different rehabilitation approaches, as well as future physiological experiments for a further understanding of postinjury mechanisms of motor control and recovery
Some Weighted Hardy-type Inequalities of Vector-Valued Functions
No full textBy adopting the C-technique of Cheung and Pečrić, we establish some interesting weighted Hardy-type inequalities of vector-valued functions. These generalize and improve some existing results of Cheung, Cheung-Hanjš-Pēcarić, Hanjš-Love-Pečarić, Levinson, and Pachpatte. [ABSTRACT FROM AUTHOR
Effect of Gravity Compensation on Upper Limb Muscle Synergies during Reaching: Preliminary Results from Healthy Subjects
No full text汉英同传中删减与增译现象的案例分析
No full textAuthor name used in this publication: 张其帆, Cheung Kay-fan AndrewTitle in Traditional Chinese: 漢英同傳中刪減與增譯現象的案例分析Journal title in Traditional Chinese: 中國翻譯2011-2012 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishedVoR allowe
Xin li ji jiu yu wei ji shi jian he zai nan zhong zuo wei gong gong wei sheng zai nan ying dui zhun bei de ce lüe
No full textCheung, Yee Lai.Thesis Ph.D. Chinese University of Hong Kong 2014.Includes bibliographical references (leaves 193-207).Abstracts and some appendixes also in Chinese.Title from PDF title page (viewed on 02, December, 2016).Cheung, Yee Lai
Characterization of Human Papillomavirus Type 58 E7 Protein Variant T20I/G63S
No full textCheung, Pui Yiu Grace.Thesis M.Phil. Chinese University of Hong Kong 2016.Includes bibliographical references (leaves ).Abstracts also in Chinese.Title from PDF title page (viewed on …)
Minority Media Production Practices and Cultural Citizenship in Hong Kong
No full textChong, Cheung Kwan Cindy.Thesis Ph.D. Chinese University of Hong Kong 2016.Includes bibliographical references (leaves ).Abstracts also in Chinese.Title from PDF title page (viewed on …)
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