15 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
Effect of Gravity Compensation on Upper Limb Muscle Synergies during Reaching: Preliminary Results from Healthy Subjects
No full textInterview with Gowthama Sannah, Propaganda Secretary of the VCK, Chennai, 26th September 2012
No full textThe compromised and ‘failing’ position of the Bahujan Samaj Party (BSP) and Republican Party of India, led one eminent commentator to urge Dalit activists and scholars to “look south because Tamil Nadu may offer some important lessons” for Dalit politics (Omvedt 2003: xvii-xviii). Tamil Nadu is indeed an interesting case study because it is one of the more developed states within India and has a long history of anti-caste politics and legislation. Despite this, it remains one of the more caste-divided regions as well. Autonomous mobilisation by Dalit groups coincided with an increase in casteist violence designed to keep the Dalits in a subordinate position (Gorringe 2006). It is only in the past decade, therefore, that Dalit parties have achieved sufficient credibility to forge alliances with established parties (Wyatt 2009). No Dalit party has been able to emulate the success of the BSP in electoral terms, but the political context here is very different (Omvedt 2003). The primary aim of Dalit parties in Tamil Nadu, rather, has been to strip ‘Dalit voters away from Dravidian parties’ (Roberts 2010: 18). Omvedt’s opinion comes in a book of speeches by the Tamil Dalit leader Thirumavalavan and she argues that the passion and vibrancy that characterised initial BSP mobilisation are captured in the fiery speeches and grass-roots mobilisation of Thirumavalavan and the Viduthalai Ciruthaigal Katchi (VCK – Liberation Panther Party) – the largest Dalit movement in Tamil Nadu. Roberts (2010) concurs with Omvedt’s assessment and argues that the Tamil Dalit movement has a wider social and political significance that extends beyond the state. In the past few years the VCK have cemented their alliance with the Dravida Munnetra Kazhagham (Dravidian Progressive Federation – DMK), one of the two main political parties in the state, and have gained entry to the political mainstream. On one hand, commentators suggest that the VCK offer a different, Dalit, way of doing politics rather than mimicking the established parties and point to welfare concessions that they have secured since allying with the DMK. Conversely, there is a widespread sense that the VCK are in danger of emulating other institutionalised movements by losing their radicalism and alienating their supporters. There are widespread allegations of corruption and profiteering, including numerous stories of VCK activists acting as brokers or middlemen in caste disputes for monetary gain. This interview was conducted as part of a research project, focused primarily on Dalit voters and activists in and around Madurai in order to understand how political subjectivities, ideas of citizenship, and perceptions of social exclusion have been reshaped by the entry of autonomous Dalit parties into the political mainstream. It is trying to understand whether and/or how the demands and critiques of Dalit movements have been integrated into the political behaviour of Dalit citizens and also the extent to which such ideas have informed the wider political sphere. Whilst interviews with Thirumavalavan frequently feature in Tamil magazines, it is much less common for those in secondary leadership positions to be able to articulate their positions. This interview with one of the leading Dalit intellectuals in the party offers a frank and reflexive account of the trials and tribulations of Dalit politics in Tamil Nadu.We invite feedback relating to this special interview, which may be communicated through the comment features of this online journal (registered users), or by directly contacting the author/contributors: Dr. Hugo Gorringe [email protected]. Gowthama Sanna [email protected] or http://gsannah.wordpress.co
Gene Expression Changes in the Motor Cortex Mediating Motor Skill Learning
No full textThe primary motor cortex (M1) supports motor skill learning, yet little is known about the genes that contribute to motor cortical plasticity. Such knowledge could identify candidate molecules whose targeting might enable a new understanding of motor cortical functions, and provide new drug targets for the treatment of diseases which impair motor function, such as ischemic stroke. Here, we assess changes in the motor-cortical transcriptome across different stages of motor skill acquisition. Adult rats were trained on a gradually acquired appetitive reach and grasp task that required different strategies for successful pellet retrieval, or a sham version of the task in which the rats received pellet reward without needing to develop the reach and grasp skill. Tissue was harvested from the forelimb motor-cortical area either before training commenced, prior to the initial rise in task performance, or at peak performance. Differential classes of gene expression were observed at the time point immediately preceding motor task improvement. Functional clustering revealed that gene expression changes were related to the synapse, development, intracellular signaling, and the fibroblast growth factor (FGF) family, with many modulated genes known to regulate synaptic plasticity, synaptogenesis, and cytoskeletal dynamics. The modulated expression of synaptic genes likely reflects ongoing network reorganization from commencement of training till the point of task improvement, suggesting that motor performance improves only after sufficient modifications in the cortical circuitry have accumulated. The regulated FGF-related genes may together contribute to M1 remodeling through their roles in synaptic growth and maturation.McGovern Institute for Brain Research at MITNational Institutes of Health (U.S.) ((NIH grant 1-RC1-NS068103-01)National Institutes of Health (U.S.) (NIH grant R01-MH084966)Roberto Rocca Education Program (Fellowship)Massachusetts Institute of Technology. Undergraduate Research Opportunities Program (Fellowship)Italy. Ministero dell'istruzione, dell'università e della ricerca (MIUR grant RBIN04H5AS)Italy. Ministero dell'istruzione, dell'università e della ricerca (MIUR grant RBLA03FLJC)Italy. Ministero dell'istruzione, dell'università e della ricerca (FIRB n. RBAP10L8TY
Acupuncture and related interventions for carpal tunnel syndrome: systematic review
No full text© The Author(s) 2019. Objective: To synthesize evidence on the effectiveness of acupuncture and related therapies for primary carpal tunnel syndrome (CTS) by conducting a systematic review of randomized controlled trials (RCTs). Data Sources: Nine databases were searched for potential RCTs from their inception till July 2019. Review Methods: RCTs which reported at least one of the three outcomes were included: symptom severity, functional status and pain. Included RCTs were appraised using the Cochrane Risk of Bias Tool. Results: A total of 10 RCTs (728 participants) were included. Majority were at high risk of bias for blinding of participants, personnel and outcome assessors. When compared to conventional medications, manual acupuncture showed significant superior effect in reducing symptom than ibuprofen (mean difference (MD) on Symptom Severity Scale (SSS)) = –5.80, 95% confidence interval (CI): −7.95 to −3.65) and prednisolone (MD = −6.50, 95% CI: −10.1, −2.86). Electroacupuncture plus splinting was more effective in reducing symptom severity than splinting alone (SSS score: MD = −0.20, 95% CI: −0.36 to −0.03). Manual acupuncture showed significantly superior effect than ibuprofen in improving functional status (Functional Status Scale (FSS): MD = −1.84, 95% CI: −2.66 to −1.02). The combination of electroacupuncture and splinting showed more improvement in functional status compared to splinting alone (FSS: MD = −6.22, 95%CI: −10.7 to −1.71). Triple treatment of acupuncture, magnetic spectrum heat lamp and splinting showed stronger pain relief than splinting alone. Conclusion: For both symptom relief and function improvement, manual acupuncture is superior to ibuprofen while electroacupuncture plus splinting outperforms splinting alone. Limited evidence showed electroacupuncture’s potential role in pain reduction
Modulating the structure of motor variability for skill learning through specific muscle synergies in elderlies and young adults
No full textObjective: Motor variability – performance variations across task repetitions – has been assumed to be undesirable. But recent studies argue that variability facilitates early motor learning by allowing exploratory search of reward-generating motion, and that variability’s structure may be modulated by neural circuits for furthering learning. What are the neural sources of learning-relevant motor variability and its modulation in humans of different ages? Methods: Elderlies and young adults played a 3-session virtual bowling while multi-muscle electromyographic signals were collected. We quantified trial-to-trial variability of muscle synergies – neuromotor control modules – and of their activations. Results: In elderlies, bowling-score gain correlated with change of activation timing variability of specific synergies, but in young adults, with variability changes of synergy-activation magnitude, and of the synergies themselves. Conclusions: Variability modulation of specific muscle synergies and their activations contribute to early motor learning. Elderly and young individuals may rely on different aspects of motor variability to drive learning
Adapting to the mechanical properties and active force of an exoskeleton by altering muscle synergies in chronic stroke survivors
No full textTitle on author’s file: Normalization of lower-limb muscle synergies during gait training with a
powered ankle exoskeleton in chronic stroke survivors202103 bcvcAccepted ManuscriptSelf-fundedPublishedGreen (AAM
