Journal articles on the topic 'Movement variabiliity'
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1
van Beers, Robert J., Patrick Haggard, and Daniel M. Wolpert. "The Role of Execution Noise in Movement Variability." Journal of Neurophysiology 91, no. 2 (February 2004): 1050–63. http://dx.doi.org/10.1152/jn.00652.2003.
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The origin of variability in goal-directed movements is not well understood. Variability can originate from several neural processes such as target localization, movement planning, and movement execution. Here we examine variability resulting from noise in movement execution. In several experiments, subjects moved their unseen hand to visual targets, under conditions which were designed to minimize the variability expected from localization and planning processes. We tested short movements in 32 directions in a center-out reaching task. The variability in the movement endpoints and in the initial movement direction varied systematically with the movement direction, with some directions having up to twice the variability of others. In a second experiment we tested four movements in the same direction but with different extents. Here, the longer movements were systematically curved, and the endpoint ellipses were not aligned with the straight line between starting and end position, but they were roughly aligned with the last part of the trajectory. We show that the variability observed in these experiments cannot be explained by planning noise but is well explained by noise in movement execution. A combination of both signal-dependent and signal-independent noise in the amplitude of the motor commands and temporal noise in their duration can explain the observed variability. Our results suggest that, in general, execution noise accounts for at least a large proportion of movement variability.
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Oostwoud Wijdenes, Leonie, Richard B. Ivry, and Paul M. Bays. "Competition between movement plans increases motor variability: evidence of a shared resource for movement planning." Journal of Neurophysiology 116, no. 3 (September 1, 2016): 1295–303. http://dx.doi.org/10.1152/jn.00113.2016.
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Do movement plans, like representations in working memory, share a limited pool of resources? If so, the precision with which each individual movement plan is specified should decrease as the total number of movement plans increases. To explore this, human participants made speeded reaching movements toward visual targets. We examined if preparing one movement resulted in less variability than preparing two movements. The number of planned movements was manipulated in a delayed response cueing procedure that limited planning to a single target ( experiment 1) or hand ( experiment 2) or required planning of movements toward two targets (or with two hands). For both experiments, initial movement direction variability was higher in the two-plan condition than in the one-plan condition, demonstrating a cost associated with planning multiple movements, consistent with the limited resource hypothesis. In experiment 3, we showed that the advantage in initial variability of preparing a single movement was present only when the trajectory could be fully specified. This indicates that the difference in variability between one and two plans reflects the specification of full motor plans, not a general preparedness to move. The precision cost related to concurrent plans represents a novel constraint on motor preparation, indicating that multiple movements cannot be planned independently, even if they involve different limbs.
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Kawano, Yui, and Mayumi Kuno-Mizumura. "Intra- and Inter-individual Movement Variability of Upper Limb Movements of Ballet Dancers." Medical Problems of Performing Artists 34, no. 3 (September 1, 2019): 132–40. http://dx.doi.org/10.21091/mppa.2019.3023.
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OBJECTIVE: This study examined intra- and inter-individual variability in upper limb movements of ballet dancers when performing flapping swan-wing movements, and it assessed differences in joint angles of upper limbs between dancers of different skill levels. METHODS: 23 female ballet dancers (3 professional, 6 advanced, and 14 intermediate dancers) and 21 age-matched females without previous dance experience participated in this study. Thirty-three reflective markers were attached to each participant’s trunk and upper limbs, and the flapping upper limb motions from Swan Lake were subsequently captured with eight optical cameras. Peak values of upper limb joint angles (shoulder, elbow, and wrist joint) were obtained, and intra- and inter-individual movement variability of each joint angle were compared between groups. RESULTS: In joint angles of the shoulder, elbow, and wrist, there were few differences among professional, advanced, and intermediate groups. The intra-individual movement variability in upward arm movements was significantly larger for professional and control groups than for advanced and intermediate groups, while in downward arm movement, variability became significantly smaller as technical level increased. Moreover, inter-individual movement variability was larger in the upward arm movement as technical level increased, and smaller in the downward arm movement for the professional group. The results suggested that the upward arm movements reflect dancers’ individual expression, while the downward arm movements reflect their technical competence at this swan-like movement. CONCLUSION: The complicated swan-like movements performed by skilled dancers in this study indicate that they execute expressive and technical components in sequence.
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Jaric, Slobodan, Charli Tortoza, Ismael F. C. Fatarelli, and Gil L. Almeida. "Effects of Direction and Curvature on Variable Error Pattern of Reaching Movements." Motor Control 3, no. 4 (October 1999): 414–23. http://dx.doi.org/10.1123/mcj.3.4.414.
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A number of studies have analyzed various indices of the final position variability in order to provide insight into different levels of neuromotor processing during reaching movements. Yet the possible effects of movement kinematics on variability have often been neglected. The present study was designed to test the effects of movement direction and curvature on the pattern of movement variable errors. Subjects performed series of reaching movements over the same distance and into the same target. However, due either to changes in starting position or to applied obstacles, the movements were performed in different directions or along the trajectories of different curvatures. The pattern of movement variable errors was assessed by means of the principal component analysis applied on the 2-D scatter of movement final positions. The orientation of these ellipses demonstrated changes associated with changes in both movement direction and curvature. However, neither movement direction nor movement curvature affected movement variable errors assessed by area of the ellipses. Therefore it was concluded that the end-point variability depends partly, but not exclusively, on movement kinematics.
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Apker, Gregory A., Timothy K. Darling, and Christopher A. Buneo. "Interacting Noise Sources Shape Patterns of Arm Movement Variability in Three-Dimensional Space." Journal of Neurophysiology 104, no. 5 (November 2010): 2654–66. http://dx.doi.org/10.1152/jn.00590.2010.
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Reaching movements are subject to noise in both the planning and execution phases of movement production. The interaction of these noise sources during natural movements is not well understood, despite its importance for understanding movement variability in neurologically intact and impaired individuals. Here we examined the interaction of planning and execution related noise during the production of unconstrained reaching movements. Subjects performed sequences of two movements to targets arranged in three vertical planes separated in depth. The starting position for each sequence was also varied in depth with the target plane; thus required movement sequences were largely contained within the vertical plane of the targets. Each final target in a sequence was approached from two different directions, and these movements were made with or without visual feedback of the moving hand. These combined aspects of the design allowed us to probe the interaction of execution and planning related noise with respect to reach endpoint variability. In agreement with previous studies, we found that reach endpoint distributions were highly anisotropic. The principal axes of movement variability were largely aligned with the depth axis, i.e., the axis along which visual planning related noise would be expected to dominate, and were not generally well aligned with the direction of the movement vector. Our results suggest that visual planning–related noise plays a dominant role in determining anisotropic patterns of endpoint variability in three-dimensional space, with execution noise adding to this variability in a movement direction-dependent manner.
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Berret, Bastien, Adrien Conessa, Nicolas Schweighofer, and Etienne Burdet. "Stochastic optimal feedforward-feedback control determines timing and variability of arm movements with or without vision." PLOS Computational Biology 17, no. 6 (June 11, 2021): e1009047. http://dx.doi.org/10.1371/journal.pcbi.1009047.
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Human movements with or without vision exhibit timing (i.e. speed and duration) and variability characteristics which are not well captured by existing computational models. Here, we introduce a stochastic optimal feedforward-feedback control (SFFC) model that can predict the nominal timing and trial-by-trial variability of self-paced arm reaching movements carried out with or without online visual feedback of the hand. In SFFC, movement timing results from the minimization of the intrinsic factors of effort and variance due to constant and signal-dependent motor noise, and movement variability depends on the integration of visual feedback. Reaching arm movements data are used to examine the effect of online vision on movement timing and variability, and test the model. This modelling suggests that the central nervous system predicts the effects of sensorimotor noise to generate an optimal feedforward motor command, and triggers optimal feedback corrections to task-related errors based on the available limb state estimate.
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Stalder, D., FM van Beest, S. Sveegaard, R. Dietz, J. Teilmann, and J. Nabe-Nielsen. "Influence of environmental variability on harbour porpoise movement." Marine Ecology Progress Series 648 (August 27, 2020): 207–19. http://dx.doi.org/10.3354/meps13412.
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The harbour porpoise Phocoena phocoena is a small marine predator with a high conservation status in Europe and the USA. To protect the species effectively, it is crucial to understand its movement patterns and how the distribution of intensively used foraging areas can be predicted from environmental conditions. Here, we investigated the influence of both static and dynamic environmental conditions on large-scale harbour porpoise movements in the North Sea. We used long-term movement data from 57 individuals tracked during 1999-2017 in a state-space model to estimate the underlying behavioural states, i.e. whether animals used area-restricted or directed movements. Subsequently, we assessed whether the probability of using area-restricted movements was related to environmental conditions using a generalized linear mixed model. Harbour porpoises were more likely to use area-restricted movements in areas with low salinity levels, relatively high chlorophyll a concentrations and low current velocity, and in areas with steep bottom slopes, suggesting that such areas are important foraging grounds for porpoises. Our study identifies environmental parameters of relevance for predicting harbour porpoise foraging hot spots over space and time in a dynamic system. The study illustrates how movement patterns and data on environmental conditions can be combined, which is valuable to the conservation of marine mammals.
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Chu, Virginia Way Tong, Dagmar Sternad, and Terence David Sanger. "Healthy and dystonic children compensate for changes in motor variability." Journal of Neurophysiology 109, no. 8 (April 15, 2013): 2169–78. http://dx.doi.org/10.1152/jn.00908.2012.
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Successful reaching requires that we plan movements to compensate for variability in motor output. Previous studies have shown that healthy adults optimally incorporate estimates of motor variability when planning a pointing task. Children with dystonia have increased variability compared with healthy children. It is not known whether they are able to compensate appropriately for the increased variability and whether this compensation leads to changes in reaching behavior. We examined healthy children and those with increased motor variability due to secondary dystonia. Using a simple virtual display, children performed a motor task where the variability of their movements was manipulated. Results showed that both subject groups changed their movement strategies in response to changes in the level of perceived motor variability. Both groups changed their strategy in a way that improved performance relative to the perceived motor variability. Importantly, dystonic children faced with decreased motor variability adapted their movement strategy to perform better and more similarly to healthy children. These findings show that both healthy and dystonic children are able to respond to changes in motor variability and alter their movement strategies.
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Laboissière, Rafael, Daniel R. Lametti, and David J. Ostry. "Impedance Control and Its Relation to Precision in Orofacial Movement." Journal of Neurophysiology 102, no. 1 (July 2009): 523–31. http://dx.doi.org/10.1152/jn.90948.2008.
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Speech production involves some of the most precise and finely timed patterns of human movement. Here, in the context of jaw movement in speech, we show that spatial precision in speech production is systematically associated with the regulation of impedance and in particular, with jaw stiffness—a measure of resistance to displacement. We estimated stiffness and also variability during movement using a robotic device to apply brief force pulses to the jaw. Estimates of stiffness were obtained using the perturbed position and force trajectory and an estimate of what the trajectory would be in the absence of load. We estimated this “reference trajectory” using a new technique based on Fourier analysis. A moving-average (MA) procedure was used to estimate stiffness by modeling restoring force as the moving average of previous jaw displacements. The stiffness matrix was obtained from the steady state of the MA model. We applied this technique to data from 31 subjects whose jaw movements were perturbed during speech utterances and kinematically matched nonspeech movements. We observed systematic differences in stiffness over the course of jaw-lowering and jaw-raising movements that were correlated with measures of kinematic variability. Jaw stiffness was high and variability was low early and late in the movement when the jaw was elevated. Stiffness was low and variability was high in the middle of movement when the jaw was lowered. Similar patterns were observed for speech and nonspeech conditions. The systematic relationship between stiffness and variability points to the idea that stiffness regulation is integral to the control of orofacial movement variability.
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Abrams, Richard A., Jay Pratt, and Alison L. Chasteen. "Aging and movement: Variability of force pulses for saccadic eye movements." Psychology and Aging 13, no. 3 (1998): 387–95. http://dx.doi.org/10.1037/0882-7974.13.3.387.
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Apker, Gregory A., and Christopher A. Buneo. "Contribution of execution noise to arm movement variability in three-dimensional space." Journal of Neurophysiology 107, no. 1 (January 2012): 90–102. http://dx.doi.org/10.1152/jn.00495.2011.
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Reaching movements are subject to noise associated with planning and execution, but precisely how these noise sources interact to determine patterns of endpoint variability in three-dimensional space is not well understood. For frontal plane movements, variability is largest along the depth axis (the axis along which visual planning noise is greatest), with execution noise contributing to this variability along the movement direction. Here we tested whether these noise sources interact in a similar way for movements directed in depth. Subjects performed sequences of two movements from a single starting position to targets that were either both contained within a frontal plane (“frontal sequences”) or where the first was within the frontal plane and the second was directed in depth (“depth sequences”). For both sequence types, movements were performed with or without visual feedback of the hand. When visual feedback was available, endpoint distributions for frontal and depth sequences were generally anisotropic, with the principal axes of variability being strongly aligned with the depth axis. Without visual feedback, endpoint distributions for frontal sequences were relatively isotropic and movement direction dependent, while those for depth sequences were similar to those with visual feedback. Overall, the results suggest that in the presence of visual feedback, endpoint variability is dominated by uncertainty associated with planning and updating visually guided movements. In addition, the results suggest that without visual feedback, increased uncertainty in hand position estimation effectively unmasks the effect of execution-related noise, resulting in patterns of endpoint variability that are highly movement direction dependent.
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Sternad, Dagmar, and Karl M. Newell. "Modeling movement variability in space and time." Behavioral and Brain Sciences 20, no. 2 (June 1997): 322. http://dx.doi.org/10.1017/s0140525x97421441.
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Plamondon & Alimi propose a universal account of trajectory formation and speed/accuracy trade-off in rapid movements but fail, because: (1) the kinematic model ignores the more fundamental dynamics of movement generation, and (2) it does not capture the essential space-time constraints of movement accuracy. Hence, the modeling lacks a biologically and behaviorally principled foundation and is driven by pragmatic function fitting.
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Lametti, Daniel R., and David J. Ostry. "Postural Constraints on Movement Variability." Journal of Neurophysiology 104, no. 2 (August 2010): 1061–67. http://dx.doi.org/10.1152/jn.00306.2010.
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Movements are inherently variable. When we move to a particular point in space, a cloud of final limb positions is observed around the target. Previously we noted that patterns of variability at the end of movement to a circular target were not circular, but instead reflected patterns of limb stiffness—in directions where limb stiffness was high, variability in end position was low, and vice versa. Here we examine the determinants of variability at movement end in more detail. To do this, we have subjects move the handle of a robotic device from different starting positions into a circular target. We use position servocontrolled displacements of the robot's handle to measure limb stiffness at the end of movement and we also record patterns of end position variability. To examine the effect of change in posture on movement variability, we use a visual motor transformation in which we change the limb configuration and also the actual movement target, while holding constant the visual display. We find that, regardless of movement direction, patterns of variability at the end of movement vary systematically with limb configuration and are also related to patterns of limb stiffness, which are likewise configuration dependent. The result suggests that postural configuration determines the base level of movement variability, on top of which control mechanisms can act to further alter variability.
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Bartlett, Roger. "Movement coordination and movement variability." Sports Biomechanics 6, no. 2 (May 2007): 119–20. http://dx.doi.org/10.1080/14763140701400931.
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Summerside, Erik M., Reza Shadmehr, and Alaa A. Ahmed. "Vigor of reaching movements: reward discounts the cost of effort." Journal of Neurophysiology 119, no. 6 (June 1, 2018): 2347–57. http://dx.doi.org/10.1152/jn.00872.2017.
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Making a movement may be thought of as an economic decision in which one spends effort to acquire reward. Time discounts reward, which predicts that the magnitude of reward should affect movement vigor: we should move faster, spending greater effort, when there is greater reward at stake. Indeed, saccade peak velocities are greater and reaction-times shorter when a target is paired with reward. In this study, we focused on human reaching and asked whether movement kinematics were affected by expectation of reward. Participants made out-and-back reaching movements to one of four quadrants of a 14-cm circle. During various periods of the experiment only one of the four quadrants was paired with reward, and the transition from reward to nonreward status of a quadrant occurred randomly. Our experiment design minimized dependence of reward on accuracy, granting the subjects wide latitude in self-selecting their movement speed, amplitude, and variability. When a quadrant was paired with reward, reaching movements had a shorter reaction time, higher peak velocity, and greater amplitude. Despite this greater vigor, movements toward the rewarded quadrant suffered from less variability: both reaction times and reach kinematics were less variable when there was expectation of reward. Importantly, the effect of reward on vigor was specific to the movement component that preceded the time of reward (outward reach), not the movement component that followed it (return reach). Our results suggest that expectation of reward not only increases vigor of human reaching but also decreases its variability. NEW & NOTEWORTHY Movements may be thought of as an economic transaction where the vigor of the movement represents the effort that the brain is willing to expend to acquire a rewarding state. We show that in reaching, reward discounts the cost of effort, producing movements with shorter reaction time, higher velocity, greater amplitude, and reduced reaction-time variability. These results complement earlier observations in saccades, suggesting a common principle of economics across modalities of motor control.
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Yan, Jin H., George E. Stelmach, Katherine T. Thomas, and Jerry R. Thomas. "Developmental Differences in Children's Ballistic Aiming Movements of the Arm." Perceptual and Motor Skills 96, no. 2 (April 2003): 589–98. http://dx.doi.org/10.2466/pms.2003.96.2.589.
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An experiment was conducted to examine the change in the relation between programming and “on-line” correction as a developmental explanation of children's arm movement performance. Each of 54 children in three age groups (5. 8, and 10 yr.) completed two types of rapid aiming arm movements in the longitudinal plane on the surface of a digitizer. Percent primary submovements and timing variability were dependent variables. Analysis suggested that the 5-yr.-olds used “on-line” monitoring during the arm movement and did not perform the movement sequence as a functional unit. Compared with 8- and 10-yr.-olds, the 5-yr.-olds planned a smaller portion of movements, executed the arm movements with more variability in time to peak velocity. The 8- and 10-yr.-olds appeared to plan their movements and execute the sequence as a unit. The developmental implications were discussed.
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Abedi Khoozani, Parisa, Dimitris Voudouris, Gunnar Blohm, and Katja Fiehler. "Reaching around obstacles accounts for uncertainty in coordinate transformations." Journal of Neurophysiology 123, no. 5 (May 1, 2020): 1920–32. http://dx.doi.org/10.1152/jn.00049.2020.
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We show that changing body geometry such as head roll results in compensatory reaching behaviors around obstacles. Specifically, we observed head roll causes changed preferred movement direction and increased trajectory curvature. As has been shown before, head roll increases movement variability due to stochastic coordinate transformations. Thus these results provide evidence that the brain must consider the added movement variability caused by coordinate transformations for accurate reach movements.
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Bo, Jin, Hannah J. Block, Jane E. Clark, and Amy J. Bastian. "A Cerebellar Deficit in Sensorimotor Prediction Explains Movement Timing Variability." Journal of Neurophysiology 100, no. 5 (November 2008): 2825–32. http://dx.doi.org/10.1152/jn.90221.2008.
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A popular theory is that the cerebellum functions as a timer for clocking motor events (e.g., initiation, termination). Consistent with this idea, cerebellar patients have been reported to show greater deficits during hand movements that repeatedly start and stop (i.e., discontinuous movements) compared with continuous hand movements. Yet, this finding could potentially be explained by an alternate theory in which the cerebellum acts as an internal model of limb mechanics. We tested whether a timing or internal model hypothesis best explains results from a circle-drawing task, where individuals trace a circle with the hand at a desired tempo. We first attempted to replicate prior results showing greater impairment for discontinuous versus continuous circling movements, and then asked whether we could improve patient performance by reducing demands in each domain. First, we slowed the movement down to reduce the need to predict and compensate for limb dynamics. Second, we supplied external timing information to reduce the need for an internal event timer. Results showed that we did not replicate the previous findings—cerebellar patients were impaired in both discontinuous and continuous movements. Slowing the movement improved cerebellar performance to near control values. The addition of an external visual timing signal paradoxically worsened timing deficits rather than mitigating them. One interpretation of these combined results is that the cerebellum is indeed functioning as an internal model and is needed to make appropriate predictions for movement initiation and termination.
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Fortrat, Jacques-Olivier, Cédric Formet, Jean Frutoso, and Claude Gharib. "Even slight movements disturb analysis of cardiovascular dynamics." American Journal of Physiology-Heart and Circulatory Physiology 277, no. 1 (July 1, 1999): H261—H267. http://dx.doi.org/10.1152/ajpheart.1999.277.1.h261.
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We hypothesized that spontaneous movements (postural adjustments and ideomotion) disturb analysis of heart rate and blood pressure variability and could explain the discrepancy between studies. We measured R-R intervals and systolic blood pressure in nine healthy sitting subjects during three protocols: 1) no movement allowed, 2) movements allowed but not standing, 3) movements and standing allowed. Heart rate and blood pressure were not altered by movements. Movements with or without standing produced a twofold or greater increase of the overall variability of R-R intervals and of the low-frequency components of spectral analysis of heart rate variability. The spectral exponent β of heart rate variability (1.123 at rest) was changed by movements (1.364), and the percentage of fractal noise (79% at rest) was increased by standing (91%, coarse-graining spectral analysis). Spontaneous movements could induce a plateau in the correlation dimensions of heart rate variability, but they changed its nonlinear predictability. We suggest that future studies on short-term cardiovascular variability should control spontaneous movements.
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Wang, Chunji, Yupeng Xiao, Etienne Burdet, James Gordon, and Nicolas Schweighofer. "The duration of reaching movement is longer than predicted by minimum variance." Journal of Neurophysiology 116, no. 5 (November 1, 2016): 2342–45. http://dx.doi.org/10.1152/jn.00148.2016.
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Whether the central nervous system minimizes variability or effort in planning arm movements can be tested by measuring the preferred movement duration and end-point variability. Here we conducted an experiment in which subjects performed arm reaching movements without visual feedback in fast-, medium-, slow-, and preferred-duration conditions. Results show that 1) total end-point variance was smallest in the medium-duration condition and 2) subjects preferred to carry out movements that were slower than this medium-duration condition. A parsimonious explanation for the overall pattern of end-point errors across fast, medium, preferred, and slow movement durations is that movements are planned to minimize effort as well as end-point error due to both signal-dependent and constant noise.
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del Mar Delgado, Maria, Maria Miranda, Silvia J. Alvarez, Eliezer Gurarie, William F. Fagan, Vincenzo Penteriani, Agustina di Virgilio, and Juan Manuel Morales. "The importance of individual variation in the dynamics of animal collective movements." Philosophical Transactions of the Royal Society B: Biological Sciences 373, no. 1746 (March 26, 2018): 20170008. http://dx.doi.org/10.1098/rstb.2017.0008.
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Animal collective movements are a key example of a system that links two clearly defined levels of organization: the individual and the group. Most models investigating collective movements have generated coherent collective behaviours without the inclusion of individual variability. However, new individual-based models, together with emerging empirical information, emphasize that within-group heterogeneity may strongly influence collective movement behaviour. Here we (i) review the empirical evidence for individual variation in animal collective movements, (ii) explore how theoretical investigations have represented individual heterogeneity when modelling collective movements and (iii) present a model to show how within-group heterogeneity influences the collective properties of a group. Our review underscores the need to consider variability at the level of the individual to improve our understanding of how individual decision rules lead to emergent movement patterns, and also to yield better quantitative predictions of collective behaviour. This article is part of the theme issue ‘Collective movement ecology’.
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Sforza, Roche, and Pichot. "Determinants of Nocturnal Cardiovascular Variability and Heart Rate Arousal Response in Restless Legs Syndrome (RLS)/Periodic Limb Movements (PLMS)." Journal of Clinical Medicine 8, no. 10 (October 4, 2019): 1619. http://dx.doi.org/10.3390/jcm8101619.
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Recent studies have suggested that restless legs syndrome is associated with an increased prevalence of cardiovascular diseases mediated by sympathetic activation occurring during periodic limb movements. The aim of this study was to establish which factors affect the degree of sympathetic activation during the basal condition and during periodic limb movements that may contribute to increased vascular risk. Fifty untreated restless legs syndrome patients aged 62.6 ± 11.1 y, free of cardiovascular diseases, were examined. Heart rate variability was calculated during wakefulness and all sleep stages, during periods with and without periodic limb movements. Heart rate changes before and after periodic limb movement onset were analyzed to assess the arousal response to periodic limb movements. Both analyses took into account the effects of age, gender, periodic limb movement duration, periodic limb movement index, periodic limb movement interval and periodicity, and magnitude of muscular activity (electromyogram power). Compared to periods without periodic limb movements, a significant increase in sympathetic activity occurred in periods with periodic limb movements, independent of age, sex and periodic limb movement characteristics. Data obtained from the cardiac arousal response to periodic limb movements showed that electromyogram power is the factor affecting sympathetic tonus. These results suggest that other factors, such as electromyogram power and individual susceptibility, should be considered in the assessment of the vascular risk related to restless legs syndrome.
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Zhao, Kunkun, Zhisheng Zhang, Haiying Wen, and Alessandro Scano. "Intra-Subject and Inter-Subject Movement Variability Quantified with Muscle Synergies in Upper-Limb Reaching Movements." Biomimetics 6, no. 4 (October 20, 2021): 63. http://dx.doi.org/10.3390/biomimetics6040063.
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Quantifying movement variability is a crucial aspect for clinical and laboratory investigations in several contexts. However, very few studies have assessed, in detail, the intra-subject variability across movements and the inter-subject variability. Muscle synergies are a valuable method that can be used to assess such variability. In this study, we assess, in detail, intra-subject and inter-subject variability in a scenario based on a comprehensive dataset, including multiple repetitions of multi-directional reaching movements. The results show that muscle synergies are a valuable tool for quantifying variability at the muscle level and reveal that intra-subject variability is lower than inter-subject variability in synergy modules and related temporal coefficients, and both intra-subject and inter-subject similarity are higher than random synergy matching, confirming shared underlying control structures. The study deepens the available knowledge on muscle synergy-based motor function assessment and rehabilitation applications, discussing their applicability to real scenarios.
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Hammerbeck, Ulrike, Nada Yousif, Damon Hoad, Richard Greenwood, Jörn Diedrichsen, and John C. Rothwell. "Chronic Stroke Survivors Improve Reaching Accuracy by Reducing Movement Variability at the Trained Movement Speed." Neurorehabilitation and Neural Repair 31, no. 6 (February 1, 2017): 499–508. http://dx.doi.org/10.1177/1545968317693112.
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Background. Recovery from stroke is often said to have “plateaued” after 6 to 12 months. Yet training can still improve performance even in the chronic phase. Here we investigate the biomechanics of accuracy improvements during a reaching task and test whether they are affected by the speed at which movements are practiced. Method. We trained 36 chronic stroke survivors (57.5 years, SD ± 11.5; 10 females) over 4 consecutive days to improve endpoint accuracy in an arm-reaching task (420 repetitions/day). Half of the group trained using fast movements and the other half slow movements. The trunk was constrained allowing only shoulder and elbow movement for task performance. Results. Before training, movements were variable, tended to undershoot the target, and terminated in contralateral workspace (flexion bias). Both groups improved movement accuracy by reducing trial-to-trial variability; however, change in endpoint bias (systematic error) was not significant. Improvements were greatest at the trained movement speed and generalized to other speeds in the fast training group. Small but significant improvements were observed in clinical measures in the fast training group. Conclusions. The reduction in trial-to-trial variability without an alteration to endpoint bias suggests that improvements are achieved by better control over motor commands within the existing repertoire. Thus, 4 days’ training allows stroke survivors to improve movements that they can already make. Whether new movement patterns can be acquired in the chronic phase will need to be tested in longer term studies. We recommend that training needs to be performed at slow and fast movement speeds to enhance generalization.
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Cos, Ignasi, Benoît Girard, and Emmanuel Guigon. "Balancing out dwelling and moving: optimal sensorimotor synchronization." Journal of Neurophysiology 114, no. 1 (July 2015): 146–58. http://dx.doi.org/10.1152/jn.00175.2015.
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Sensorimotor synchronization is a fundamental skill involved in the performance of many artistic activities (e.g., music, dance). After a century of research, the manner in which the nervous system produces synchronized movements remains poorly understood. Typical rhythmic movements involve a motion and a motionless phase (dwell). The dwell phase represents a sizable fraction of the rhythm period, and scales with it. The rationale for this organization remains unexplained and is the object of this study. Twelve participants, four drummers (D) and eight nondrummers (ND), performed tapping movements paced at 0.5–2.5 Hz by a metronome. The participants organized their tapping behavior into dwell and movement phases according to two strategies: 1) Eight participants (1 D, 7 ND) maintained an almost constant ratio of movement time (MT) and dwell time (DT) irrespective of the metronome period. 2) Four participants increased the proportion of DT as the period increased. The temporal variabilities of both the dwell and movement phases were consistent with Weber's law, i.e., their variability increased with their durations, and the longest phase always exhibited the smallest variability. We developed an optimal statistical model that formalized the distribution of time into dwell and movement intervals as a function of their temporal variability. The model accurately predicted the participants' dwell and movement durations irrespective of their strategy and musical skill, strongly suggesting that the distribution of DT and MT results from an optimization process, dependent on each participant's skill to predict time during rest and movement.
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Stergiou, Nicholas, Regina T. Harbourne, and James T. Cavanaugh. "Optimal Movement Variability." Journal of Neurologic Physical Therapy 30, no. 3 (September 2006): 120–29. http://dx.doi.org/10.1097/01.npt.0000281949.48193.d9.
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Madansingh, Stefan, and Stacey L. Gorniak. "Using Nonlinear Tools to Evaluate Movement of Fragile Objects." Journal of Applied Biomechanics 31, no. 2 (April 2015): 95–101. http://dx.doi.org/10.1123/jab.2014-0056.
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We investigated the movement strategies of young, healthy participants (7 men/7 women) during the movement of a fragile object using nonlinear analysis. The kinematic variables of position, velocity, and acceleration were quantified using largest Lyapunov exponent (LyE) and approximate entropy (ApEn) analysis to identify the structure of their movement variability and movement predictability, respectively. Subjects performed a total of 15 discrete trials of an upper extremity movement task without crushing the object at each fragility condition, using each hand (left/right). We tested four fragility conditions hypothesizing that an increase in fragility would result in higher movement predictability and decreased temporal variability. Comparisons between the structure of movement variability and movement predictability were based on fragility condition, handedness, and kinematic measures. In this specific population, object fragility and participant handedness did not significantly impact the structure of movement variability (LyE) in the primary direction of movement (Z direction), although some effects were observed in the anterior/posterior directions. ApEn values were minimized across conditions, showing increased movement predictability, and is suggested for the analysis of discrete kinematic movements. In healthy populations, the results of this study suggest minimal effects on task performance and movement predictability as a result of object fragility.
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Levy-Tzedek, S., M. Ben Tov, and A. Karniel. "Rhythmic movements are larger and faster but with the same frequency on removal of visual feedback." Journal of Neurophysiology 106, no. 5 (November 2011): 2120–26. http://dx.doi.org/10.1152/jn.00266.2011.
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The brain controls rhythmic movement through neural circuits combining visual information with proprioceptive information from the limbs. Although rhythmic movements are fundamental to everyday activities the specific details of the responsible control mechanisms remain elusive. We tested 39 young adults who performed flexion/extension movements of the forearm. We provided them with explicit knowledge of the amplitude and the speed of their movements, whereas frequency information was only implicitly available. In a series of 3 experiments, we demonstrate a tighter control of frequency compared with amplitude or speed. We found that in the absence of visual feedback, movements had larger amplitude and higher peak speed while maintaining the same frequency as when visual feedback was available; this was the case even when participants were aware of performing overly large and fast movements. Finally, when participants were asked to modulate continuously movement frequency, but not amplitude, we found the local coefficient of variability of movement frequency to be lower than that of amplitude. We suggest that a misperception of the generated amplitude in the absence of visual feedback, coupled with a highly accurate perception of generated frequency, leads to the performance of larger and faster movements with the same frequency when visual feedback is not available. Relatively low local coefficient of variability of frequency in a task that calls for continuous change in movement frequency suggests that we tend to operate at a constant frequency at the expense of variation in amplitude and peak speed.
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Moiseev, Sergey A., Aleksandr M. Pukhov, Ekaterina A. Mikhaylova, Asiat T. Gafarova, and Ruslan M. Gorodnichev. "Variability of Technical Action Coordination Structure in Boxing at Fatigue." Journal of Medical and Biological Research, no. 1 (February 10, 2021): 35–44. http://dx.doi.org/10.37482/2687-1491-z041.
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One of the directions of research into movement variability studies it at changing external or internal conditions during motor task performance. The results of such investigations are ambivalent even when analysing movements with similar kinematic structure. The aim of the research was to study the variability of skeletal muscle bioelectric activity and space-time characteristics of various punches in boxing at fatigue. Six highly skilled boxers of different weight classes were involved. We analysed parameters of variation of muscle electromyographic activity, distance and speed of the anthropometric points of body segments, as well as joint movement amplitude under regular conditions and after an aerobic motor load. We found low amplitude variability in most of the skeletal muscles under study, both in regular conditions and after a motor load. At fatigue, amplitude variability of almost all muscles decreased. Under regular conditions, the movement amplitude of the shoulder, elbow and hip joints on the bodyʼs right side was more varied than that in the joints on the left. After a motor load, changes in the variability of joint movement amplitude during the performance of different punches were dissimilar. The most variable were changes in the angles of the right side of the body, especially the elbow and hip joints, when performing a direct punch. The least changes under the load were observed in the movement amplitude of the elbow and hip joints on the left side. Thus, variability changes in kinematic parameters caused by skeletal muscle activity are a mechanism for maintaining stability of motor task performance. Presumably, the central neural control of complex coordination movements in boxers when performing punches is carried out through the formation of kinematic and muscle synergies. More research is needed to clarify the mechanism of formation and functioning of kinematic synergies and their variability.
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Buchman-Pearle, Jessa M., David C. Kingston, and Stacey M. Acker. "Lower Limb Movement Pattern Differences Between Males and Females in Squatting and Kneeling." Journal of Applied Biomechanics 37, no. 3 (June 1, 2021): 204–14. http://dx.doi.org/10.1123/jab.2020-0185.
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Movement pattern differences may contribute to differential injury or disease prevalence between individuals. The purpose of this study was to identify lower limb movement patterns in high knee flexion, a risk factor for knee osteoarthritis, and to investigate kinematic differences between males and females, as females typically develop knee osteoarthritis more commonly and severely than males. Lower extremity kinematic data were recorded from 110 participants completing 4 variations of squatting and kneeling. Principal component analysis was used to identify principal movements associated with the largest variability in the sample. Across the tasks, similar principal movements emerged at maximal flexion and during transitions. At maximal flexion, females achieved greater knee flexion, facilitated by a wider base of support, which may alter posterior and lateral tibiofemoral stress. Principal movements also detected differences in movement temporality between males and females. When these temporal differences occur due to alterations in movement velocity and/or acceleration, they may elicit changes in muscle activation and knee joint stress. Movement variability identified in the current study provides a framework for potential modifiable factors in high knee flexion, such as foot position, and suggests that kinematic differences between the sexes may contribute to differences in knee osteoarthritis progression.
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Stejskal, Vladimír. "Geomorphological aspects of monitoring movements of rock blocks in pseudocarst localities Ostaš, Hejda and Kočičí skály." Geografie 110, no. 2 (2005): 82–90. http://dx.doi.org/10.37040/geografie2005110020082.
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Since 1989 slope movements and movements of tectonic origin have been monitored in three pseudocarst localities in Polická vrchovina. Monitoring has allowed to detect more or less distinct manifestations of slope movement activity in the majority of observing points. A detailed geomorphological analysis has shown time variability of the mechanism of slope movements. Presence of movements of tectonic origin hasn't been proved.
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Nóbrega, Lígia Reis, Ariana Moura Cabral, Fábio Henrique Monteiro Oliveira, Adriano de Oliveira Andrade, Sridhar Krishnan, and Adriano Alves Pereira. "Wrist Movement Variability Assessment in Individuals with Parkinson’s Disease." Healthcare 10, no. 9 (August 30, 2022): 1656. http://dx.doi.org/10.3390/healthcare10091656.
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(1) Background: Parkinson’s disease (PD) is a neurodegenerative disorder represented by the progressive loss of dopamine-producing neurons, it decreases the individual’s motor functions and affects the execution of movements. There is a real need to include quantitative techniques and reliable methods to assess the evolution of PD. (2) Methods: This cross-sectional study assessed the variability of wrist RUD (radial and ulnar deviation) and FE (flexion and extension) movements measured by two pairs of capacitive sensors (PS25454 EPIC). The hypothesis was that PD patients have less variability in wrist movement execution than healthy individuals. The data was collected from 29 participants (age: 62.13 ± 9.7) with PD and 29 healthy individuals (60.70 ± 8). Subjects performed the experimental tasks at normal and fast speeds. Six features that captured the amplitude of the hand movements around two axes were estimated from the collected signals. (3) Results: The movement variability was greater for healthy individuals than for PD patients (p < 0.05). (4) Conclusion: The low variability seen in the PD group may indicate they execute wrist RUD and FE in a more restricted way. The variability analysis proposed here could be used as an indicator of patient progress in therapeutic programs and required changes in medication dosage.
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Seidler-Dobrin, Rachael D., jiping He, and George E. Stelmach. "Coactivation to Reduce Variability in the Elderly." Motor Control 2, no. 4 (October 1998): 314–30. http://dx.doi.org/10.1123/mcj.2.4.314.
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The aim of this experiment was to determine whether elderly persons exhibit reciprocal phasing of muscle activity and scale EMG burst amplitude in the same manner as young people. Seven young and 7 elderly adults performed 30° elbow flexion movements at 800 ms duration to a visual target against varying inertial loads. The elderly were not able to achieve the required movement duration as frequently and spent a greater portion of the movement accelerating than the young. The young and the elderly subjects scaled EMG burst amplitude to the increasing loads in the same fashion, although the elderly subjects coactivated the agonisthtagonist muscles more than did the young subjects and thus did not accelerate the limb as rapidly. We hypothesized that the elderly used coactivation to reduce movement variability, and we developed a single-joint model with two muscles to examine this hypothesis. The model simulation correctly predicted the variability reduction due to coactivation. It appears, however, that this reduces the capability to accelerate rapidly.
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Wiltshire, Charlotte E. E., Mark Chiew, Jennifer Chesters, Máiréad P. Healy, and Kate E. Watkins. "Speech Movement Variability in People Who Stutter: A Vocal Tract Magnetic Resonance Imaging Study." Journal of Speech, Language, and Hearing Research 64, no. 7 (July 16, 2021): 2438–52. http://dx.doi.org/10.1044/2021_jslhr-20-00507.
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Purpose People who stutter (PWS) have more unstable speech motor systems than people who are typically fluent (PWTF). Here, we used real-time magnetic resonance imaging (MRI) of the vocal tract to assess variability and duration of movements of different articulators in PWS and PWTF during fluent speech production. Method The vocal tracts of 28 adults with moderate to severe stuttering and 20 PWTF were scanned using MRI while repeating simple and complex pseudowords. Midsagittal images of the vocal tract from lips to larynx were reconstructed at 33.3 frames per second. For each participant, we measured the variability and duration of movements across multiple repetitions of the pseudowords in three selected articulators: the lips, tongue body, and velum. Results PWS showed significantly greater speech movement variability than PWTF during fluent repetitions of pseudowords. The group difference was most evident for measurements of lip aperture using these stimuli, as reported previously, but here, we report that movements of the tongue body and velum were also affected during the same utterances. Variability was not affected by phonological complexity. Speech movement variability was unrelated to stuttering severity within the PWS group. PWS also showed longer speech movement durations relative to PWTF for fluent repetitions of multisyllabic pseudowords, and this group difference was even more evident as complexity increased. Conclusions Using real-time MRI of the vocal tract, we found that PWS produced more variable movements than PWTF even during fluent productions of simple pseudowords. PWS also took longer to produce multisyllabic words relative to PWTF, particularly when words were more complex. This indicates general, trait-level differences in the control of the articulators between PWS and PWTF. Supplemental Material https://doi.org/10.23641/asha.14782092
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Winiarski, Sławomir, Ivan Malagoli Lanzoni, and Ziemowit Bańkosz. "The Role of the Non-Playing Hand during Topspin Forehand in Table Tennis." Symmetry 13, no. 11 (November 1, 2021): 2054. http://dx.doi.org/10.3390/sym13112054.
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Theoretical tutorials and the scientific literature do not provide information on the proper use of the non-playing hand in table tennis. This study aimed to evaluate the course of the movement in the joints of the non-playing limb during a table tennis topspin forehand stroke (played after a backspin ball) and to determine the inter-individual movement variability. The study involved 12 male table tennis players (178.7 ± 5.5 cm, 70.0 ± 6.6 kg, 23 ± 3 y) at a competitive level. The participants performed one topspin forehand as a response to a backspin ball. Kinematics were measured using an Inertial Motion Unit–MR3 myoMuscle Master Edition system. Changes in the angles of the upper limb joints (with particular emphasis on the non-playing hand) during the forehand topspin were analyzed. A novel method of normalized function of variance was used to characterize areas of high/low variability of movement. Most of the movements in the joints of the non-playing limb were performed symmetrically to the playing one, especially in the hitting phase. A rapid change of direction characterizes these movements, just before or during the hitting phase, which may indicate a supportive, ‘driving’ character for these movements. High inter-individual variability for the duration of the entire movement cycle in both limbs was observed; higher in the non-playing limb. This perhaps indicates a greater degree of individualization on the non-playing side.
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Rider, Kevin A., and Bernard J. Martin. "Effects of Ride Motion on the Speed and Accuracy of In-Vehicle Pointing Tasks." Proceedings of the Human Factors and Ergonomics Society Annual Meeting 49, no. 12 (September 2005): 1119–23. http://dx.doi.org/10.1177/154193120504901204.
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Terrain-induced vibration of a moving vehicle adversely affects the ability to quickly and accurately perform in-vehicle pointing tasks by altering the planned fingertip trajectory. The relationship between movement speed and accuracy is a result of the combined use of visual and somatosensory feedbacks which are used to discern movement deviations and make necessary compensatory movements. Participants (N=20) performed three-dimensional rapid pointing tasks under stationary and ride motion conditions to three touchpanel displays. Ride motion contributed to increased reaction and movement times and increased endpoint variability. Trajectory deviations were correlated to the principal direction of vehicle acceleration. Reaches orthogonal to the dominant vehicle acceleration exhibited larger endpoint variability, and reaches to the elevated touchpanel resulted in the largest variability across all motion conditions. Principal axes of endpoint ellipses were along the on-axis and off-axis directions of fingertip movement.
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Clark, Logan D., and Sara L. Riggs. "Movement Strategies in Virtual Reality: Exploring the Influence of 3D Endpoint Variability." Proceedings of the Human Factors and Ergonomics Society Annual Meeting 65, no. 1 (September 2021): 91–95. http://dx.doi.org/10.1177/1071181321651101.
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Research using a kinematic approach has revealed that users often exhibit strategic biases in their movement behavior to minimize the effort required to reach a target. However, a recent exploration of these effects in a virtual reality (VR) environment yielded conflicting results, calling into question whether strategic patterns observed in movements to physical targets can be expected to generalize to VR environments. In the present study, we re-analyze the data from Clark and Riggs (2020) using principal component analysis (PCA) to empirically distinguish between alternative explanations for the unexpected results. Our findings clarify the source of these results for downward versus upward movements and provide a preliminary look at how adaptations to manage perception- and execution-related motor variability may impact users’ movement strategies in VR.
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Gibbons, Cameron T., Polemnia G. Amazeen, and Aaron D. Likens. "Distinguishing Two Types of Variability in a Sit-to-Stand Task." Motor Control 24, no. 1 (January 1, 2020): 168–88. http://dx.doi.org/10.1123/mc.2018-0022.
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Variability is commonly observed in complex behavior, such as the maintenance of upright posture. The current study examines the value added by using nonlinear measures of variability to identify dynamic stability instead of linear measures that reflect average fluctuations about a mean state. The largest Lyapunov exponent (λ1) and SD were calculated on mediolateral movement as participants performed a sit-to-stand task on a stable and unstable platform. Both measures identified changes in movement across postures, but results diverged when participants stood on the unstable platform. Large SD indicated an increase in movement variability, but small λ1 identified those movements as stable and controlled. The results suggest that a combination of linear and nonlinear analyses is useful in identifying the proportion of observed variability that may be attributed to structured, controlled sources. Nonlinear measures of variability, like λ1, can further be used to make predictions about transitions between stable postures and to identify a system’s resistance to disruption from external perturbations. Those features make nonlinear analyses highly applicable to both human movement research and clinical practice.
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Roy, Eric A., and Digby Elliott. "Manual Asymmetries in Aimed Movements." Quarterly Journal of Experimental Psychology Section A 41, no. 3 (August 1989): 501–16. http://dx.doi.org/10.1080/14640748908402379.
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Three hypotheses for the right-hand advantage in aiming movements were examined in these experiments: (1) the right-hand system is more efficient at processing visual information during the movement; (2) subjects make more use of visual information prior to movement initiation when using the right hand; (3) the right hand is less variable in generating force in initiating the pointing response as force demands increase. In the first experiment subjects pointed at a target located directly in front of them from two starting positions which defined short (25-cm) and long (35-cm) movements. The movements were made in three movement times, fast (150 to 249 msec), medium (250 to 349 msec) and slow (350 to 449 msec), under three vision conditions—full vision, and no vision (lights out) with immediate or delayed movement initiation. Performance was measured in movement time and accuracy in amplitude of movement. The results did not completely support any of the hypotheses regarding the right-hand advantage, although the left hand was generally more variable than the right. Also, variability increased with increases in movement length and decreases in movement time. The second experiment was designed to examine further the hypotheses regarding the right-hand advantage. In this experiment the same three visual conditions were used; however, subjects made only fast (<250-msec) movements. Also six rather than two starting positions were used. The increased variability of the left hand was observed again here. Further pointing accuracy with the left hand was more adversely affected in the no-vision delay condition. The implications of these results were discussed as they pertain to understanding the processes involved in visual aiming and the observed manual asymmetries.
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Crevecoeur, F., J. McIntyre, J. L. Thonnard, and P. Lefèvre. "Movement Stability Under Uncertain Internal Models of Dynamics." Journal of Neurophysiology 104, no. 3 (September 2010): 1301–13. http://dx.doi.org/10.1152/jn.00315.2010.
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Sensory noise and feedback delay are potential sources of instability and variability for the on-line control of movement. It is commonly assumed that predictions based on internal models allow the CNS to anticipate the consequences of motor actions and protect the movements from uncertainty and instability. However, during motor learning and exposure to unknown dynamics, these predictions can be inaccurate. Therefore a distinct strategy is necessary to preserve movement stability. This study tests the hypothesis that in such situations, subjects adapt the speed and accuracy constraints on the movement, yielding a control policy that is less prone to undesirable variability in the outcome. This hypothesis was tested by asking subjects to hold a manipulandum in precision grip and to perform single-joint, discrete arm rotations during short-term exposure to weightlessness (0 g), where the internal models of the limb dynamics must be updated. Measurements of grip force adjustments indicated that the internal predictions were altered during early exposure to the 0 g condition. Indeed, the grip force/load force coupling reflected that the grip force was less finely tuned to the load-force variations at the beginning of the exposure to the novel gravitational condition. During this learning period, movements were slower with asymmetric velocity profiles and target undershooting. This effect was compared with theoretical results obtained in the context of optimal feedback control, where changing the movement objective can be directly tested by adjusting the cost parameters. The effect on the simulated movements quantitatively supported the hypothesis of a change in cost function during early exposure to a novel environment. The modified optimization criterion reduces the trial-to-trial variability in spite of the fact that noise affects the internal prediction. These observations support the idea that the CNS adjusts the movement objective to stabilize the movement when internal models are uncertain.
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Bøe, Kristin, Michael Power, Martha J. Robertson, Corey J. Morris, J. Brian Dempson, Curtis J. Pennell, and Ian A. Fleming. "The influence of temperature and life stage in shaping migratory patterns during the early marine phase of two Newfoundland (Canada) Atlantic salmon (Salmo salar) populations." Canadian Journal of Fisheries and Aquatic Sciences 76, no. 12 (December 2019): 2364–76. http://dx.doi.org/10.1139/cjfas-2018-0320.
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Owing to the iteroparous nature of Atlantic salmon (Salmo salar), a seaward migrating cohort may consist of juveniles and adults that differ in size, maturity, experience, and in the motivation and consequences of migratory movements. Few studies have investigated the role of ontogeny in shaping intrapopulation variability in movement patterns among Atlantic salmon monitored under the same environmental conditions. This study contrasted the movements of smolts and kelts in two Canadian (Newfoundland) populations from marine entry through coastal embayments and quantified the influence of local water temperatures on movement patterns. Significant differences in migration routes, migration speed, and diel movements between smolts and kelts were present. Kelts generally displayed faster, more directed, and less nocturnal movements compared with smolts. Temperature influenced seaward movement positively, as well as the degree of diurnal movement. Prolonged nearshore residency by smolts and kelts in the two embayments was accompanied by a considerable improvement in ocean thermal conditions, hypothesized to promote open ocean entry during conditions favorable to migration performance.
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Lametti, Daniel R., Guillaume Houle, and David J. Ostry. "Control of Movement Variability and the Regulation of Limb Impedance." Journal of Neurophysiology 98, no. 6 (December 2007): 3516–24. http://dx.doi.org/10.1152/jn.00970.2007.
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Humans routinely make movements to targets that have different accuracy requirements in different directions. Examples extend from everyday occurrences such as grasping the handle of a coffee cup to the more refined instance of a surgeon positioning a scalpel. The attainment of accuracy in situations such as these might be related to the nervous system's capacity to regulate the limb's resistance to displacement, or impedance. To test this idea, subjects made movements from random starting locations to targets that had shape-dependent accuracy requirements. We used a robotic device to assess both limb impedance and patterns of movement variability just as the subject reached the target. We show that impedance increases in directions where required accuracy is high. Independent of target shape, patterns of limb stiffness are seen to predict spatial patterns of movement variability. The nervous system is thus seen to modulate limb impedance in entirely predictable environments to aid in the attainment of reaching accuracy.
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Titov, Vitaliy B., and Natalya I. Kuzevanova. "Atmospheric circulation and variability of meteorological elements in near-shore Black Sea region." Hydrosphere Еcology (Экология гидросферы), no. 1(6) (2021): 85–94. http://dx.doi.org/10.33624/2587-9367-2021-1(6)-85-94.
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Effect of solar radiation and atmospheric circulation on variability of air temperature, atmospheric pressure, and rainfall in near-shore Black Sea region was examined. The action of the latitudinal position of trajectory cyclonic and anticyclonic movements and their times of occurrence in seasonal variability of meteorological elements was established. Three factor action on cyclonican and anticyclonic movement latitudinal position was determined. This is air temperature (year cycle), North-Atlantic oscillation, and lunar weather tides. Seasonal times of occurrence of cyclon and anticyclone, movements of southerly and northerly trajectories, and variability of atmospheric pressure and rainfall in near-shore Black Sea region was estimated.
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Steele, Catriona M., and Pascal H. H. M. Van Lieshout. "Use of Electromagnetic Midsagittal Articulography in the Study of Swallowing." Journal of Speech, Language, and Hearing Research 47, no. 2 (April 2004): 342–52. http://dx.doi.org/10.1044/1092-4388(2004/027).
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The tongue functions as the primary articulator during the oropharyngeal stages of swallowing. However, detailed descriptions of the kinematics and spatiotemporal variability of tongue behaviors during swallowing are limited to a handful of analyses of data from the X-ray microbeam database. In this article, a new technique, electromagnetic midsagittal articulography (EMMA), is introduced for the high-resolution description of oral articulatory movements during swallowing. Data from 8 healthy, nondysphagic participants are used to illustrate the methods used for data collection and analysis. Movement data were collected for 3 fleshpoint positions on the tongue (blade, body, dorsum) during sequences of repeated discrete water swallows, and were characterized for variables of spatiotemporal variability and 4 discrete kinematic parameters (movement amplitude, peak velocity, duration, and kinematic stiffness). These data show that the movement trajectories measured using EMMA are consistent with descriptions from previous X-ray microbeam studies, indicating that EMMA is a feasible method for the detailed study of tongue movements during swallowing.
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Donnet, Sophie, Ramon Bartolo, José Maria Fernandes, João Paulo Silva Cunha, Luis Prado, and Hugo Merchant. "Monkeys time their pauses of movement and not their movement-kinematics during a synchronization-continuation rhythmic task." Journal of Neurophysiology 111, no. 10 (May 15, 2014): 2138–49. http://dx.doi.org/10.1152/jn.00802.2013.
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A critical question in tapping behavior is to understand whether the temporal control is exerted on the duration and trajectory of the downward-upward hand movement or on the pause between hand movements. In the present study, we determined the duration of both the movement execution and pauses of monkeys performing a synchronization-continuation task (SCT), using the speed profile of their tapping behavior. We found a linear increase in the variance of pause-duration as a function of interval, while the variance of the motor implementation was relatively constant across intervals. In fact, 96% of the variability of the duration of a complete tapping cycle (pause + movement) was due to the variability of the pause duration. In addition, we performed a Bayesian model selection to determine the effect of interval duration (450–1,000 ms), serial-order (1–6 produced intervals), task phase (sensory cued or internally driven), and marker modality (auditory or visual) on the duration of the movement-pause and tapping movement. The results showed that the most important parameter used to successfully perform the SCT was the control of the pause duration. We also found that the kinematics of the tapping movements was concordant with a stereotyped ballistic control of the hand pressing the push-button. The present findings support the idea that monkeys used an explicit timing strategy to perform the SCT, where a dedicated timing mechanism controlled the duration of the pauses of movement, while also triggered the execution of fixed movements across each interval of the rhythmic sequence.
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van Donkelaar, P., and R. G. Lee. "Interactions between the eye and hand motor systems: disruptions due to cerebellar dysfunction." Journal of Neurophysiology 72, no. 4 (October 1, 1994): 1674–85. http://dx.doi.org/10.1152/jn.1994.72.4.1674.
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1. We tested the hypothesis that interactions occur between eye and hand movements produced in conjunction. This was accomplished by having human subjects with cerebellar dysfunction and age-matched controls perform two tasks: 1) tracking a moving target with the hand and 2) performing a pointing movement to intercept the target. Our prediction was that the inaccuracies that are characteristic of eye and hand movements generated in isolation by cerebellar subjects would be accentuated in each system during combined eye-hand tasks. 2. The cerebellar subjects took longer to respond to the onset of target motion in both tasks. This was true for both the eyes and hand, regardless of whether the eye and hand movements were generated in isolation or in conjunction with each other. 3. The cerebellar subjects also displayed a larger degree of error and/or variability in their hand movements than the control subjects. A significant amount of this increased variability was due to systematic changes in the trajectory of the hand during the critical periods leading up to and after each ocular saccade. These systematic changes were consistent with an overestimation of target velocity in the perifoveal visual field. 4. The increased variability of the cerebellar subjects' hand movements was markedly reduced by restricting eye movements. A similar reduction in variability occurred when vision of the hand was restricted in the tracking task. This effect was accompanied by improved eye movements. 5. For both sets of subjects the eye movements were affected by the hand movements produced in the tracking task. In particular, eye movement accuracy was improved in the controls and degraded in the cerebellar subjects when compared with the eye movements generated in isolation. In contrast, no changes were observed in the interception task. 6. Taken together, these results imply that a reciprocal interaction occurs between the eye and hand motor systems and/or that common “upstream” sites influence each of these systems in a similar manner. The functional anatomy and neurophysiological characteristics of several sites where such interactions may take place are discussed.
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Mateo, Julio C., Robert H. Gilkey, and Jeffrey L. Cowgill. "Effect of Variable Visual-Feedback Delay on Movement Time." Proceedings of the Human Factors and Ergonomics Society Annual Meeting 51, no. 19 (October 2007): 1373–77. http://dx.doi.org/10.1177/154193120705101921.
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The effects of variable feedback delays on movement time were examined in a three-dimensional (3D) virtual environment. The participants' task was to use a 3D controller to position a cursor in targets as they appeared in a cubic workspace. Both the mean and standard deviation of the delay between the movement of the controller and the displayed position of the cursor were manipulated. In addition, the size of the targets and the distance between targets were varied. The results suggested that movement times are much more strongly affected by mean delay than by delay variability and that the effect of both variables is greatest during the closed-loop component of the movement. The results are discussed in relation to buffering strategies for reducing delay variability, Fitts' law, and other descriptions of aimed movements.
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Zheng, Bin, and Christine L. MacKenzie. "The Control Strategy for Degrees of Freedom in Remote Prehension with a Tool." Proceedings of the Human Factors and Ergonomics Society Annual Meeting 51, no. 19 (October 2007): 1358–62. http://dx.doi.org/10.1177/154193120705101918.
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Constructing movement couplings is essential for decreasing degrees-of-freedom for a compound movement that requires coordination over a multiple segments. Angular movements of joints in the upper limbs are examined, the pattern of movement couplings between prehension performed with the hands (natural prehension) and with a simple grasper held in the hands (remote prehension). In remote prehension, the shoulder and elbow joint are tightly associated with a clear in-phase joint to joint movement; the elbow and wrist display both anti- and in-phase movements due to the change of initial configuration of the upper limb when holding a tool. In contrast, the shoulder-elbow bond is mixed in natural prehension, but the elbow and wrist bond is predominant with an anti-phase pattern. With diversity for joint couplings, the movement consistency of the hinge is preserved with relatively smaller path variability. Results support the end-point control notion, i.e. movement is controlled by extrinsic coordinates close to the end-effectors of the movement system.
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Maurer-Grubinger, Christian, Jasmin Haenel, Laura Fraeulin, Fabian Holzgreve, Eileen M. Wanke, David A. Groneberg, and Daniela Ohlendorf. "The Movement Profile of Habitual Vacuuming as a Cyclic Movement—A Pilot Study." International Journal of Environmental Research and Public Health 17, no. 23 (November 26, 2020): 8793. http://dx.doi.org/10.3390/ijerph17238793.
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Background: Vacuum cleaning, which is associated with musculoskeletal complaints, is frequently carried out in private households and by professional cleaners. The aim of this pilot study was to quantify the movements during habitual vacuuming and to characterize the movement profile with regard to its variability. Methods: The data were collected from 31 subjects (21 f/10 m) using a 3D motion analysis system (XSens). Eight vacuum cleaners were used to vacuum polyvinyl chloride (PVC) and carpet floors. In 15 joints of the right upper extremity, the trunk and the lower extremities, Principal Component Analysis was used to determine the predominantly varying joints during vacuuming. Results: The movements of the trunk and the lower extremities were relatively constant and, therefore, had less influence. The shoulder, elbow and wrist joints were identified as joints that can be decisive for the movement profile and that can be influenced. These joints were represented in the course of the vacuuming cycle by the mean movement with its standard deviation. Conclusion: In summary, the generalization of a movement profile is possible for the trunk and the lower extremities due to the relative homogeneity. In future it will be necessary to identify factors influencing variability in order to draw conclusions about movement ergonomics.
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Roberts, James W., James Maiden, and Gavin P. Lawrence. "Sequential aiming in pairs: the multiple levels of joint action." Experimental Brain Research 239, no. 5 (March 8, 2021): 1479–88. http://dx.doi.org/10.1007/s00221-021-06060-5.
Full textAbstract:
AbstractThe task constraints imposed upon a co-actor can often influence our own actions. Likewise, the observation of somebody else’s movements can involuntarily contaminate the execution of our own movements. These joint action outcomes have rarely been considered in unison. The aim of the present study was to simultaneously examine the underlying processes contributing to joint action. We had pairs of participants work together to execute sequential aiming movements between two targets—the first person’s movement was contingent upon the anticipation of the second person’s movement (leader), while the second person’s movement was contingent upon the direct observation of the first person’s movement (follower). Participants executed separate blocks of two-target aiming movements under different contexts; that is, solely on their own using one (2T1L) and two (2T2L) of their upper limbs, or with another person (2T2P). The first movement segment generally indicated a more abrupt approach (shorter time after peak velocity, greater displacement and magnitude of peak velocity), which surprisingly coincided with lower spatial variability, for the 2T2P context. Meanwhile, the second segment indicated a similar kinematic profile as the first segment for the 2T2P context. The first movement of the leader appeared to accommodate the follower for their movement, while the second movement of the follower was primed by the observation of the leader’s movement. These findings collectively advocate two distinct levels of joint action including the anticipation (top–down) and mapping (bottom–up) of other people’s actions.