The Experts below are selected from a list of 17334 Experts worldwide ranked by ideXlab platform
Dylan J Edwards - One of the best experts on this subject based on the ideXlab platform.
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reversal of tms induced motor Twitch by training is associated with a reduction in excitability of the antagonist Muscle
Journal of Neuroengineering and Rehabilitation, 2011Co-Authors: Viola Giacobbe, Bruce T Volpe, Gary W Thickbroom, Felipe Fregni, Alvaro Pascualleone, Hermano Igo Krebs, Dylan J EdwardsAbstract:Background A single session of isolated repetitive movements of the thumb can alter the response to transcranial magnetic stimulation (TMS), such that the related Muscle Twitch measured post-training occurs in the trained direction. This response is attributed to transient excitability changes in primary motor cortex (M1) that form the early part of learning. We investigated; (1) whether this phenomenon might occur for movements at the wrist, and (2) how specific TMS activation patterns of opposing Muscles underlie the practice-induced change in direction.
Paul M L Janssen - One of the best experts on this subject based on the ideXlab platform.
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Muscle Twitch kinetics are dependent on Muscle group disease state and age in duchenne muscular dystrophy mouse models
Frontiers in Physiology, 2020Co-Authors: Kyra K Peczkowski, Neha Rastogi, Jeovanna Lowe, Kyle T Floyd, Eric J Schultz, Tallib Karaze, Jonathan P Davis, Jill A Rafaelfortney, Paul M L JanssenAbstract:Duchenne muscular dystrophy (DMD) is an X-linked disorder caused by the lack of functional dystrophin protein. In muscular dystrophy preclinical research, it is pertinent to analyze the force of the Muscles affected by the disease to assess pathology and potential effectiveness of therapeutic interventions. Although Muscles function at sub-maximal levels in vivo, maximal tetanic contractions are most commonly used to assess and report Muscle function in muscular dystrophy studies. At submaximal activation, the kinetics of contraction and relaxation are heavily impacted by the kinetics of the single Twitch. However, maximal tetanic force is often the main, if not sole, outcome measured in most studies, while contractile kinetics are rarely reported. To investigate the effect of Muscle disease on Twitch contraction kinetics, isolated diaphragm and extensor digitorum longus (EDL) Muscles of 10-, 20-week, "het" (dystrophin deficient and utrophin haplo-insufficient), and 52-week mdx (dystrophin deficient) mice were analyzed and compared to wild-type controls. We observed that Twitch contractile kinetics are dependent on Muscle type, age, and disease state. Specific findings include that diaphragm from wildtype mice has a greater time to 50% relaxation (RT50) than time to peak tension (TTP) compared to the het and mdx dystrophic models, where there is a similar TTP compared to RT50. Diaphragm Twitch kinetics remain virtually unchanged with age, while the EDL from het and mdx mice initially has a greater RT50 than TTP, but the TTP increases with age. The difference between EDL contractile kinetics of dystrophic and wildtype mice is more prominent at young age. Differences in kinetics yielded greater statistical significance compared to previously published force measurements, thus, using kinetics as an outcome parameter could potentially allow for use of smaller experimental groups in future study designs. Although this study focused on DMD models, our findings may be applicable to other skeletal Muscle conditions and diseases.
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decrease in sarcoplasmic reticulum calcium content not myofilament function contributes to Muscle Twitch force decline in isolated cardiac trabeculae
Journal of Muscle Research and Cell Motility, 2014Co-Authors: Nima Milaninejad, Lucia Brunello, Sandor Gyorke, Paul M L JanssenAbstract:We set out to determine the factors responsible for Twitch force decline in isolated intact rat cardiac trabeculae. The contractile force of trabeculae declined over extended periods of isometric Twitch contractions. The force-frequency relationship within the frequency range of 4–8 Hz, at 37 °C, became more positive and the frequency optimum shifted to higher rates with this decline in baseline Twitch tensions. The post-rest potentiation (37 °C), a phenomenon highly dependent on calcium handling mechanisms, became more pronounced with decrease in Twitch tensions. We show that the main abnormality during Muscle run-down was not due to a deficit in the myofilaments; maximal tension achieved using a K+ contracture protocol was either unaffected or only slightly decreased. Conversely, the sarcoplasmic reticulum (SR) calcium content, as assessed by rapid cooling contractures (from 27 to 0 °C), decreased, and had a close association with the declining Twitch tensions (R2 ~ 0.76). SR Ca2+-ATPase, relative to Na+/Ca2+ exchanger activity, was not altered as there was no significant change in paired rapid cooling contracture ratios. Furthermore, confocal microscopy detected no abnormalities in the overall structure of the cardiomyocytes and t-tubules in the cardiac trabeculae (~23 °C). Overall, the data indicates that the primary mechanism responsible for force run-down in multi-cellular cardiac preparations is a decline in the SR calcium content and not the maximal tension generation capability of the myofilaments.
Christian Grefkes - One of the best experts on this subject based on the ideXlab platform.
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What Makes the Muscle Twitch: Motor System Connectivity and TMS-Induced Activity
Cerebral Cortex, 2015Co-Authors: Lukas J. Volz, John C Rothwell, Masashi Hamada, Christian GrefkesAbstract:Transcranial magnetic stimulation (TMS) of the primary motor cortex (M1) evokes several volleys of corticospinal activity. While the earliest wave (D-wave) originates from axonal activation of cortico-spinal neurons (CSN), later waves (I-waves) result from activation of mono- and polysynaptic inputs to CSNs. Different coil orientations preferentially stimulate cortical elements evoking different outputs: latero-medial-induced current (LM) elicits D-waves and short-latency electromyographic responses (MEPs); posterior-anterior current (PA) evokes early I-waves. Anterior-posterior current (AP) is more variable and tends to recruit later I-waves, featuring longer onset latencies compared with PA-TMS. We tested whether the variability in response to AP-TMS was related to functional connectivity of the stimulated M1 in 20 right-handed healthy subjects who underwent functional magnetic resonance imaging while performing an isometric contraction task. The MEP-latency after AP-TMS (relative to LM-TMS) was strongly correlated with functional connectivity between the stimulated M1 and a network involving cortical premotor areas. This indicates that stronger premotor-M1 connectivity increases the probability that AP-TMS recruits shorter latency input to CSNs. In conclusion, our data strongly support the hypothesis that TMS of M1 activates distinct neuronal pathways depending on the orientation of the stimulation coil. Particularly, AP currents seem to recruit short latency cortico-cortical projections from premotor areas.
Felipe Fregni - One of the best experts on this subject based on the ideXlab platform.
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reversal of tms induced motor Twitch by training is associated with a reduction in excitability of the antagonist Muscle
Journal of Neuroengineering and Rehabilitation, 2011Co-Authors: Viola Giacobbe, Bruce T Volpe, Gary W Thickbroom, Felipe Fregni, Alvaro Pascualleone, Hermano Igo Krebs, Dylan J EdwardsAbstract:Background A single session of isolated repetitive movements of the thumb can alter the response to transcranial magnetic stimulation (TMS), such that the related Muscle Twitch measured post-training occurs in the trained direction. This response is attributed to transient excitability changes in primary motor cortex (M1) that form the early part of learning. We investigated; (1) whether this phenomenon might occur for movements at the wrist, and (2) how specific TMS activation patterns of opposing Muscles underlie the practice-induced change in direction.
Alvaro Pascualleone - One of the best experts on this subject based on the ideXlab platform.
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reversal of tms induced motor Twitch by training is associated with a reduction in excitability of the antagonist Muscle
Journal of Neuroengineering and Rehabilitation, 2011Co-Authors: Viola Giacobbe, Bruce T Volpe, Gary W Thickbroom, Felipe Fregni, Alvaro Pascualleone, Hermano Igo Krebs, Dylan J EdwardsAbstract:Background A single session of isolated repetitive movements of the thumb can alter the response to transcranial magnetic stimulation (TMS), such that the related Muscle Twitch measured post-training occurs in the trained direction. This response is attributed to transient excitability changes in primary motor cortex (M1) that form the early part of learning. We investigated; (1) whether this phenomenon might occur for movements at the wrist, and (2) how specific TMS activation patterns of opposing Muscles underlie the practice-induced change in direction.
