799 resultados para MOVEMENT COORDINATION


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Social interaction is a core aspect of human life that affects individuals’ physical and mental health. Social interaction usually leads to mutual engagement in diverse areas of mental, emotional, physiological and physical activity involving both interacting persons and subsequently impacting the outcome of interactions. A common approach to the analysis of social interaction is the study of the verbal content transmitted between sender and receiver. However, additional important processes and dynamics are occurring in other domains too, for example in the area of nonverbal behaviour: In a series of studies, we have looked at nonverbal synchrony – the coordination of two persons’ movement patterns – and it‘s association with relationship quality and with the outcome of interactions. Using a computer-based algorithm (Motion Energy Analysis, MEA: Ramseyer & Tschacher, 2011), which automatically quantifies a person‘s body-movement, we were able to objectively calculate nonverbal synchrony in a large number of dyads interacting in various settings. In a first step, we showed that the phenomenon of nonverbal synchrony exists at a level that is significantly higher than expected by chance. In a second step, we ascertained that across different settings – including patient-therapist dyads and healthy dyads – more synchronized movement was associated with better relationship quality and better interactional outcomes. The quality of a relationship is thus embodied by the synchronized movement patterns emerging between partners. Our studies suggest that embodied cognition is a valuable approach to research in social interaction, providing important clues for an improved understanding of interaction dynamics.

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When individual amoebae of the cellular slime mold Dictyostelium discoideum are starving, they aggregate to form a multicellular migrating slug, which moves toward a region suitable for culmination. The culmination of the morphogenesis involves complex cell movements that transform a mound of cells into a globule of spores on a slender stalk. The movement has been likened to a “reverse fountain,” whereby prestalk cells in the upper part form a stalk that moves downwards and anchors to the substratum, while prespore cells in the lower part move upwards to form the spore head. So far, however, no satisfactory explanation has been produced for this process. Using a computer simulation that we developed, we now demonstrate that the processes that are essential during the earlier stages of the morphogenesis are in fact sufficient to produce the dynamics of the culmination stage. These processes are cAMP signaling, differential adhesion, cell differentiation, and production of extracellular matrix. Our model clarifies the processes that generate the observed cell movements. More specifically, we show that periodic upward movements, caused by chemotactic motion, are essential for successful culmination, because the pressure waves they induce squeeze the stalk downwards through the cell mass. The mechanisms revealed by our model have a number of self-organizing and self-correcting properties and can account for many previously unconnected and unexplained experimental observations.

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It has often been supposed that patterns of rhythmic bimanual coordination in which homologous muscles are engaged simultaneously, are performed in a more stable manner than those in which the same muscles are activated in an alternating fashion. In order to assess the efficacy of this constraint, the present study investigated the effect of forearm posture (prone or supine) on bimanual abduction-adduction movements of the wrist in isodirectional and non-isodirectional modes of coordination. Irrespective of forearm posture, non-isodirectional coordination was observed to be more stable than isodirectional coordination. In the latter condition, there was a more severe deterioration of coordination accuracy/stability as a function of cycling frequency than in the former condition. With elevations in cycling frequency, the performers recruited extra mechanical degrees of freedom, principally via flexion-extension of the wrist, which gave rise to increasing motion in the vertical plane. The increases in movement amplitude in the vertical plane were accompanied by decreasing amplitude in the horizontal plane. In agreement with previous studies, the present findings confirm that the relative timing of homologous muscle activation acts as a principal constraint upon the stability of interlimb coordination. Furthermore, it is argued that the use of manipulations of limb posture to investigate the role of other classes of constraint (e.g. perceptual) should be approached with caution because such manipulations affect the mapping between muscle activation patterns, movement dynamics and kinematics.

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To examine the role of the effector dynamics of the wrist in the production of rhythmic motor activity, we estimated the phase shifts between the EMG and the task-related output for a rhythmic isometric torque production task and an oscillatory movement, and found a substantial difference (45-52degrees) between the two. For both tasks, the relation between EMG and task-related output (torque or displacement) was adequately reproduced with a physiologically motivated musculoskeletal model. The model simulations demonstrated the importance of the contribution of passive structures to the overall dynamics and provided an account for the observed phase shifts in the dynamic task. Additional simulations of the musculoskeletal model with added load suggested that particular changes in the phase relation between EMG and movement may follow largely from the intrinsic muscle dynamics, rather than being the result of adaptations in the neural control of joint stiffness. The implications of these results are discussed in relation to (models of) interlimb coordination in rhythmic tasks. (C) 2004 Elsevier B.V. All rights reserved.

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This study explored the use of advance information in the control of reach-to-grasp movements. The paradigm required participants to reach and grasp illuminated blocks with their right hand. Four target blocks were positioned on a table surface, two each side of the mid-saggital plane. In the complete precue condition, advance information precisely specified target location. In the partial precue condition, advance information indicated target location relative to the midsaggital plane (left or right). In the null condition, the advance information was entirely ambiguous. Participants produced fastest responses in the complete precue condition, intermediate response times in the partial condition, and the slowest responses in the null condition. This result was observed in adults and four groups of children including a group aged 4-6 years. In contrast, children with Developmental Coordination Disorder (DCD, n = 11, aged 7-13 years) showed no advantage of partial precueing. Movement duration was determined by target location but was unaffected by precue condition. Movement duration was a clear function of age apart from children in the DCD group who showed equivalent movement times to those of the youngest children. These findings provide important insights into the control of reach-to-grasp movements and highlight that partial cues are exploited by children as young as 4 years but are not used in situations of abnormal development.

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In this experiment, we examined the extent to which the spatiotemporal reorganization of muscle synergies mediates skill acquisition on a two degree-of-freedom (df) target-acquisition task. Eight participants completed five practice sessions on consecutive days. During each session they practiced movements to eight target positions presented by a visual display. The movements required combinations of flexion/extension and pronation/supination of the elbow joint complex. During practice sessions, eight targets displaced 5.4 cm from the start position ( representing joint excursions of 54) were presented 16 times. During pre- and posttests, participants acquired the targets at two distances (3.6 cm [36 degrees] and 7.2 cm [72 degrees]). EMG data were recorded from eight muscles contributing to the movements during the pre- and posttests. Most targets were acquired more rapidly after the practice period. Performance improvements were, in most target directions, accompanied by increases in the smoothness of the movement trajectories. When target acquisition required movement in both dfs, there were also practice-related decreases in the extent to which the trajectories deviated from a direct path to the target. The contribution of monofunctional muscles ( those producing torque in a single df) increased with practice during movements in which they acted as agonists. The activity in bifunctional muscles ( those contributing torque in both dfs) remained at pretest levels in most movements. The results suggest that performance gains were mediated primarily by changes in the spatial organization of muscles synergies. These changes were expressed most prominently in terms of the magnitude of activation of the monofunctional muscles.

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Patellofemoral pain (PFP) may be related to unfavorable knee joint loading. Delayed and/or reduced activity of vastus medialis obliquus (VMO) and different movement patterns have been identified in individuals with PFP in some studies, whereas other studies have failed to show a difference compared to non-affected controls. The discrepancy between study results may depend on the different tasks that have been investigated. No previous study has investigated these variables in postural responses to unpredictable perturbations in PFP. Whole body three dimensional kinematics and surface EMG of quadriceps muscles activation was studied in postural responses to unpredictable support surface translations in 17 women with PFP who were pain free at the time of testing, and 17 matched healthy controls. The results of the present study showed earlier onset of VMO activity and associated changes in kinematics to anterior platform translation in the PFP subjects. We suggest that the relative timing between the portions quadriceps muscles may be task specific and part of an adapted response in attempt to reduce knee joint loading. This learned response appears to remain even when the pain is no longer present.

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Why and under what conditions have the Kurds become agents of change in the Middle East in terms of democratization? Why did the Kurds' role as democratic agents become particularly visible in the 1990s? How does the Kurdish movement's turn to democratic discourse affect the political systems of Turkey, Iran, Iraq and Syria? What are the implications of the Kurds' adoption of "democratic discourse" for the transnational aspect of the Kurdish movement? Since the early 1990s, Kurdish national movements in Turkey, Iran, Iraq and Syria have undergone important political and ideological transformations. As a result of the Kurds' growing role in shaping the debates on human rights and democratization in these four countries, the Kurdish national movement has acquired a dual character: an ethno-cultural struggle for the recognition of Kurdish identity, and a democratization movement that seeks to redefine the concepts of governance and citizenship in Turkey, Iran, Iraq and Syria. The process transformation has affected relations between the Kurdish movements and their respective central governments in significant ways. On the basis of face-to-face interviews and archival research conducted in Turkey, Iraq and parts of Europe, the present work challenges the current narrative of Kurdish nationalism, which is predominantly drawn from a statist interpretation of Kurdish nationalist goals, and argues instead that the Kurdish question is no longer a problem of statelessness but a problem of democracy in Turkey, Iran, Iraq and Syria. The main contributions of this work are three fold. First, the research unfolds the reasons behind the growing emphasis of the Kurdish movement on the concepts of democracy, human rights, and political participation, which started in the early 1990s. Second, the findings challenge the existing scholarship that explains Kurdish nationalism as a problem of statelessness and shifts the focus to the transformative potentials of the Kurdish national movement in Turkey, Iran, Iraq and Syria through a comparative lens. Third, this work explores the complex transnational coordination and negotiations between the Kurdish movements across borders and explains the regional repercussions of this process.

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Changes in olfactory-mediated behaviour caused by elevated CO2 levels in the ocean could affect recruitment to reef fish populations because larval fish become more vulnerable to predation. However, it is currently unclear how elevated CO2 will impact the other key part of the predator-prey interaction - the predators. We investigated the effects of elevated CO2 and reduced pH on olfactory preferences, activity levels and feeding behaviour of a common coral reef meso-predator, the brown dottyback (Pseudochromis fuscus). Predators were exposed to either current-day CO2 levels or one of two elevated CO2 levels (~600 µatm or ~950 µatm) that may occur by 2100 according to climate change predictions. Exposure to elevated CO2 and reduced pH caused a shift from preference to avoidance of the smell of injured prey, with CO2treated predators spending approximately 20% less time in a water stream containing prey odour compared with controls. Furthermore, activity levels of fish was higher in the high CO2 treatment and feeding activity was lower for fish in the mid CO2treatment; indicating that future conditions may potentially reduce the ability of the fish to respond rapidly to fluctuations in food availability. Elevated activity levels of predators in the high CO2 treatment, however, may compensate for reduced olfactory ability, as greater movement facilitated visual detection of food. Our findings show that, at least for the species tested to date, both parties in the predator-prey relationship may be affected by ocean acidification. Although impairment of olfactory-mediated behaviour of predators might reduce the risk of predation for larval fishes, the magnitude of the observed effects of elevated CO2 acidification appear to be more dramatic for prey compared to predators. Thus, it is unlikely that the altered behaviour of predators is sufficient to fully compensate for the effects of ocean acidification on prey mortality.

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The well-known degrees of freedom problem originally introduced by Nikolai Bernstein (1967) results from the high abundance of degrees of freedom in the musculoskeletal system. Such abundance in motor control have two sides: i) because it is unlikely that the Central Nervous System controls each degree of freedom independently, the complexity of the control needs to be reduced, and ii) because there are many options to perform a movement, a repetition of a given movement is never the same. It leads to two main topics in motor control and biomechanics: motor coordination and motor variability. The present thesis aimed to understand how motor systems behave and adapt under specific conditions. This thesis comprises three studies that focused on three topics of major interest in the field of sports sciences and medicine: expertise, injury risk and fatigue. The first study (expertise) has focused on the muscle coordination topic to further investigate the effect of expertise on the muscle synergistic organization, which ultimately may represent the underlying neural strategies. Studies 2 (excessive medial knee displacement) and 3 (fatigue) both aimed to better understand its impact on the dynamic local stability. The main findings of the present thesis suggest: 1) there is a great robustness in muscle synergistic organization between swimmers at different levels of expertise (study 1, chapter II), which ultimately indicate that differences in muscle coordination is mainly explained by peripheral adaptations; 2) injury risk factors such as excessive medial knee displacement (study 2, chapter III) and fatigue (study 3, chapter IV) alter the dynamic local stability of the neuromuscular system towards a more unstable state. This change in dynamic local stability represents a loss of adaptability in the neuromuscular system reducing the flexibility to adapt to a perturbation.

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The electrocardiogram (ECG) is the simplest and most effective non-invasive method to assess the electrical activity of the heart and to obtain information on the heart rate (HR) and rhythm. Because information on the HR of very small reptiles (body mass <10 g) is still scarce in the literature, in the present work we describe a procedure for recording the ECG in non-anesthetized geckos (Hemidactylus mabouia, Moreau de Jonnès, 1818) under different conditions, namely manual restraint (MR), spontaneous tonic immobility (TI), and in the non-restrained condition (NR). In the gecko ECG, the P, QRS and T waves were clearly distinguishable. The HR was 2.83 ± 0.02 Hz under MR, which was significantly greater (p < 0.001) than the HR under the TI (1.65 ± 0.09 Hz) and NR (1.60 ± 0.10 Hz) conditions. Spontaneously beating isolated gecko hearts contracted at 0.84 ± 0.03 Hz. The in vitro beating rate was affected in a concentration-dependent fashion by adrenoceptor stimulation with noradrenaline, as well as by the muscarinic cholinergic agonist carbachol, which produced significant positive and negative chronotropic effects, respectively (p < 0.001). To our knowledge, this is the first report on the ECG morphology and HR values in geckos, particularly under TI. The methodology and instrumentation developed here are useful for non-invasive in vivo physiological and pharmacological studies in small reptiles without the need of physical restraint or anesthesia.

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This article is part of a study considering the growing importance of the international transit of people, knowledge, and practices in the schooling and professional education processes of some social segments. Considering the public funds made available by the Coordination for the Improvement of Higher Education Personnel - Capes -, the National Council for Scientific and Technological Development - CNPq - and the State of São Paulo Research Foundation - Fapesp - to support researchers' fellowships abroad, aming to improve research and investments on Science and Technology on the context of international exchanges, we have dedicated this article to the preliminary description and analysis of the database of fellows funded abroad by these research agencies from 1970 to 2000. The movement of flows based on the quantitative methodology of the correlation of variables draws the trends of international academic exchange programs in the three research institutions and in the different areas of knowledge, and we intend to analyse them taking into account the scientific and technological development policies adopted by Brazilian State on the period.