Artykuły w czasopismach na temat „Arm – Movements”
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Sorrento, Gianluca U., i Denise Y. P. Henriques. "Reference Frame Conversions for Repeated Arm Movements". Journal of Neurophysiology 99, nr 6 (czerwiec 2008): 2968–84. http://dx.doi.org/10.1152/jn.90225.2008.
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The aim of this study was to further understand how the brain represents spatial information for shaping aiming movements to targets. Both behavioral and neurophysiological studies have shown that the brain represents spatial memory for reaching targets in an eye-fixed frame. To date, these studies have only shown how the brain stores and updates target locations for generating a single arm movement. But once a target's location has been computed relative to the hand to program a pointing movement, is that information reused for subsequent movements to the same location? Or is the remembered target location reconverted from eye to motor coordinates each time a pointing movement is made? To test between these two possibilities, we had subjects point twice to the remembered location of a previously foveated target after shifting their gaze to the opposite side of the target site before each pointing movement. When we compared the direction of pointing errors for the second movement to those of the first, we found that errors for each movement varied as a function of current gaze so that pointing endpoints fell on opposite sides of the remembered target site in the same trial. Our results suggest that when shaping multiple pointing movements to the same location the brain does not use information from the previous arm movement such as an arm-fixed representation of the target but instead mainly uses the updated eye-fixed representation of the target to recalculate its location into the appropriate motor frame.
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Flash, Tamar, i Ealan Henis. "Arm Trajectory Modifications During Reaching Towards Visual Targets". Journal of Cognitive Neuroscience 3, nr 3 (lipiec 1991): 220–30. http://dx.doi.org/10.1162/jocn.1991.3.3.220.
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In this paper we study the question of how an aimed arm movement is modified in response to a sudden change in target location occurring during the reaction or movement time. Earlier monkey and human studies demonstrated that aimed arm movements can be elicited in quick succession, without appreciable delays in responding to the target displacement, beyond the normal reaction time. Nevertheless, it is not yet clear how this motor task is performed. A first guess is that when a new visual stimulus appears the old plan is aborted and a new one conceived. Upon analyzing human arm movements, however, we find that the observations can be well accounted for by a different movement modification scheme. It appears that a new plan is vectorially added to the original plan. Among the implications of this result is the possibility of parallel planning of elemental movements and further support for the idea that arm movements are internally represented in terms of hand motion through external space.
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Fisk, J., J. R. Lackner i P. DiZio. "Gravitoinertial force level influences arm movement control". Journal of Neurophysiology 69, nr 2 (1.02.1993): 504–11. http://dx.doi.org/10.1152/jn.1993.69.2.504.
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1. The ability to move the forearm between remembered elbow joint angles immediately after rapid increases or decreases of the background gravitoinertial force (G) level was measured. The movements had been well-practiced in a normal 1G environment before the measurements in high-(1.8G) and low-force (0G) environments. The forearm and upper arm were always unsupported to maximize the influence of altered G-loading and to minimize extraneous cues about arm position. 2. Horizontal and vertical movement planes were studied to measure the effects of varying the G load in the movement plane within a given G background. Rapid and slow movements were studied to assess the role of proprioceptive feedback. 3. G level did not affect the amplitude of rapid movements, indicating that subjects were able to plan and to generate appropriate motor commands for the new G loading of the arm. The amplitude of slow movements was affected by G level, indicating that proprioceptive feedback is influenced by G level. 4. The effects of G level were similar for horizontal and vertical movements, indicating that proprioceptive information from supporting structures, such as the shoulder joint and muscles, had a role in allowing generation of the appropriate motor commands. 5. The incidence and size of dynamic overshoots were greater in 0G and for rapid movements. This G-related change in damping suggests a decrease in muscle spindle activity in 0G. A decrease in muscle spindle activity in 0G and an increase in 1.8G are consistent with the results of our prior studies on the tonic vibration reflex, locomotion, and perception of head movement trajectory in varying force backgrounds.
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Boulton, Hayley, i Suvobrata Mitra. "Body posture modulates imagined arm movements and responds to them". Journal of Neurophysiology 110, nr 11 (1.12.2013): 2617–26. http://dx.doi.org/10.1152/jn.00488.2013.
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Imagined movements are thought to simulate physical ones, with similar behavioral constraints and neurophysiological activation patterns and with an inhibition mechanism that suppresses movement execution. When upper body movements such as reaching with the arm are made from an upright stance, lower body and trunk muscles are also activated to maintain body posture. It is not clear to what extent parameters of imagined manual movements are sensitive to the postural adjustments their execution would necessitate, nor whether such postural responses are as effectively inhibited as the imagined movements themselves. We asked healthy young participants to imagine reaching movements of the arm while in upright stance, and we measured their self-reported movement times and postural sway during imagined movements. We manipulated mediolateral stance stability and the direction of arm movement (mediolateral or anteroposterior). Imagined arm movements were reportedly slower when subjects were standing in a mediolaterally less stable stance, and the body swayed more when arm movements were imagined in the direction of postural vulnerability. The results suggest that the postural state of the whole body, not just the involved limbs, informs trajectory planning during motor imagery and that measurable adjustments to body posture accompany imagined manual actions. It has been suggested that movement is suppressed during motor imagery by a premotor inhibitory mechanism operating at brain stem or spinal level. Any such inhibition must be incomplete because, for example, it does not eliminate autonomic arousal. Our results suggest that it also does not effectively suppress postural adjustments planned in support of imagined movements.
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Cos, Ignasi, Nicolas Bélanger i Paul Cisek. "The influence of predicted arm biomechanics on decision making". Journal of Neurophysiology 105, nr 6 (czerwiec 2011): 3022–33. http://dx.doi.org/10.1152/jn.00975.2010.
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There is considerable debate on the extent to which biomechanical properties of movements are taken into account before and during voluntary movements. For example, while several models have described reach planning as primarily kinematic, some studies have suggested that implicit knowledge about biomechanics may also exert some influence on the planning of reaching movements. Here, we investigated whether decisions about reaching movements are influenced by biomechanical factors and whether these factors are taken into account before movement onset. To this end, we designed an experimental paradigm in which humans made free choices between two potential reaching movements where the options varied in path distance as well as biomechanical factors related to movement energy and stability. Our results suggest that the biomechanical properties of potential actions strongly influence the selection between them. In particular, in our task, subjects preferred movements whose final trajectory was better aligned with the major axis of the arm's mobility ellipse, even when the launching properties were very similar. This reveals that the nervous system can predict biomechanical properties of potential actions before movement onset and that these predictions, in addition to purely abstract criteria, may influence the decision-making process.
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.V, Ramya, Prasanalakshmi .V, Ranjani M. .P, Revathi .G i Rajeswari .P. "Upper Arm Exoskeleton Using Robotic Arm for Physiotherapy". International Journal of Emerging Research in Management and Technology 6, nr 8 (25.06.2018): 190. http://dx.doi.org/10.23956/ijermt.v6i8.137.
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Stroke is a major cause of disability in worldwide and also one of the causes of death after coronary heart disease. Many devices had been designed for hand motor function rehabilitation that a stroke survivor can use for bilateral movement practice. This paper deals with the rehabilitation of upper arm by an Arm exoskeleton. This can be used for physical therapy and to assist the user with routine activities. Ultimately, the user should feel as if they are in control of their arm without too much effort while providing smooth movements depending on the direction that is desired.
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Brooks, V. B., i S. L. Watts. "Adaptive Programing of Arm Movements". Journal of Motor Behavior 20, nr 2 (czerwiec 1988): 117–32. http://dx.doi.org/10.1080/00222895.1988.10735437.
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Berret, B., J. P. Gauthier i C. Papaxanthis. "How humans control arm movements". Proceedings of the Steklov Institute of Mathematics 261, nr 1 (lipiec 2008): 44–58. http://dx.doi.org/10.1134/s0081543808020053.
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Cham, Rakié, i Peter N. Sandrian. "Arm Movements and Slip Severity". Proceedings of the Human Factors and Ergonomics Society Annual Meeting 51, nr 15 (październik 2007): 904–8. http://dx.doi.org/10.1177/154193120705101508.
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Slip-initiated falls often cause occupational injuries and deaths, especially in older workers. Previous slips and falls research has to a large extent focused on lower extremity reactions, yet arm responses are often part of postural reactions to such perturbations. It is unclear if arm responses play a role in balance recovery, are modulated by the severity of the postural perturbation and/or are a reflex-type response, e.g. reaching for external body support. In this study, the relationship between slip severity and shoulder biomechanics was examined. Subjects (17 younger and 12 older adults) were exposed to two conditions: (1) baseline dry (subjects knew the floor was dry), and (2) unexpected slip (a diluted glycerol solution was spread on the floor to slip the leading/left foot). Bilateral sagittal plane kinematics and kinetics were derived. Slip severity was quantified using a measure of slip hazardousness based on the peak slip velocity (PSV) measured at the heel of the slipping foot. Specifically, if PSV ≥ 1 m/s, then the slip was classified as hazardous. Although arm responses were bilateral, only the biomechanics of the shoulder ipsilateral to the slipping foot, specifically moment generation rate, were affected by slip hazardousness. Specifically, a hazardous slip was associated with an extensor moment at the shoulder ipsilateral to the slipping foot, whereas a non-hazardous slip was associated with a flexor moment. Shoulder responses were triggered later than the hip and knee response based on moment onset data. Finally, overall, older adults appeared to generate a greater extensor moment at the shoulder compared to the response seen in the younger group of participants. In conclusion, evidence presented in this study implies that (1) arm responses play a role in balance recovery but also may be protective in nature when experiencing a severe slip, (2) a legs-to-arms response sequence appears to drive the reaction to a slip, and (3) older adults may use their arms as a protective strategy to a greater extent than their younger counterparts.
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Scaliti, Eugenio, Emanuele Gruppioni i Cristina Becchio. "And Yet It Moves: What We Currently Know about Phantom Arm Movements". Neuroscientist 26, nr 4 (28.02.2020): 328–42. http://dx.doi.org/10.1177/1073858420904326.
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What is left over if I subtract the fact that my arm goes up from the fact that I raise my arm? Neurological evidence invites the provocative hypothesis that what is left over is a phantom arm movement—a movement of an arm that has been amputated. After arm/hand amputation, many amputees report that they can generate voluntary movements of the phantom limb; that is, they can move the arm that was amputated. But what is it like to move an arm/hand that is not there? Here, we review what is currently known about phantom limb movements at three descriptive levels: the kinematic level, the muscle level, and the cortical level. We conclude that phantom arm movements are best conceptualized as the real movements of a dematerialized hand.
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Yan, Jin H., George E. Stelmach, Katherine T. Thomas i Jerry R. Thomas. "Developmental Differences in Children's Ballistic Aiming Movements of the Arm". Perceptual and Motor Skills 96, nr 2 (kwiecień 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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Sciutti, Alessandra, Laurent Demougeot, Bastien Berret, Simone Toma, Giulio Sandini, Charalambos Papaxanthis i Thierry Pozzo. "Visual gravity influences arm movement planning". Journal of Neurophysiology 107, nr 12 (15.06.2012): 3433–45. http://dx.doi.org/10.1152/jn.00420.2011.
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When submitted to a visuomotor rotation, subjects show rapid adaptation of visually guided arm reaching movements, indicated by a progressive reduction in reaching errors. In this study, we wanted to make a step forward by investigating to what extent this adaptation also implies changes into the motor plan. Up to now, classical visuomotor rotation paradigms have been performed on the horizontal plane, where the reaching motor plan in general requires the same kinematics (i.e., straight path and symmetric velocity profile). To overcome this limitation, we considered vertical and horizontal movement directions requiring specific velocity profiles. This way, a change in the motor plan due to the visuomotor conflict would be measurable in terms of a modification in the velocity profile of the reaching movement. Ten subjects performed horizontal and vertical reaching movements while observing a rotated visual feedback of their motion. We found that adaptation to a visuomotor rotation produces a significant change in the motor plan, i.e., changes to the symmetry of velocity profiles. This suggests that the central nervous system takes into account the visual information to plan a future motion, even if this causes the adoption of nonoptimal motor plans in terms of energy consumption. However, the influence of vision on arm movement planning is not fixed, but rather changes as a function of the visual orientation of the movement. Indeed, a clear influence on motion planning can be observed only when the movement is visually presented as oriented along the vertical direction. Thus vision contributes differently to the planning of arm pointing movements depending on motion orientation in space.
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Jones, Keith S., i Benjamin P. Widlus. "Do exploratory arm movements contribute to maximum reach distance judgements?" Quarterly Journal of Experimental Psychology 73, nr 9 (19.03.2020): 1301–10. http://dx.doi.org/10.1177/1747021820911045.
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Exploratory movements provide information about agents’ action capabilities in a given environment. However, little is known about the specifics of these exploratory movements, such as which movements are necessary to perceive a given action capability. This experiment tested whether arm movements contributed to judgements of maximum reach distance. Participants made judgements about their maximum reach distance by walking to the point farthest from an object from which they still perceived the object to be reachable. Over the course of two sets of nine judgements, participants’ arms either swung naturally by their sides (Unrestricted Condition) or were held together behind their backs (Restricted Condition). Arm movement restriction increased maximum reach distance judgement error when compared with unrestricted judgements. In addition, judgement error improved over trials only when exploratory arm movements were unrestricted, and the improvements did not carry over to subsequent judgements made when exploratory arm movements were restricted. Arm movement restriction did not increase the variability of judgement error when compared with unrestricted judgements. The results indicate that exploration is necessary to generate affordance information, show that restricted exploration degrades affordance perception, and suggest that maximum reach distance exists at the global array level. In addition, they have practical implications for operational situations in which actors’ arm movements are restricted, such as when military personnel wear body armour.
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Boyle, Jason B., i Charles H. Shea. "Micro-movements of varying difficulties: wrist and arm movements". Experimental Brain Research 229, nr 1 (4.06.2013): 61–73. http://dx.doi.org/10.1007/s00221-013-3590-5.
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Takatoku, Nozomi, i Motoko Fujiwara. "Control of Arm Movements for Quick Change of Movement Direction". Journal of Motor Behavior 46, nr 1 (28.10.2013): 25–32. http://dx.doi.org/10.1080/00222895.2013.840554.
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Gribble, Paul L., David J. Ostry, Vittorio Sanguineti i Rafael Laboissière. "Are Complex Control Signals Required for Human Arm Movement?" Journal of Neurophysiology 79, nr 3 (1.03.1998): 1409–24. http://dx.doi.org/10.1152/jn.1998.79.3.1409.
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Gribble, Paul L., David J. Ostry, Vittorio Sanguineti, and Rafael Laboissière. Are complex control signals required for human arm movement? J. Neurophysiol. 79: 1409–1424, 1998. It has been proposed that the control signals underlying voluntary human arm movement have a “complex” nonmonotonic time-varying form, and a number of empirical findings have been offered in support of this idea. In this paper, we address three such findings using a model of two-joint arm motion based on the λ version of the equilibrium-point hypothesis. The model includes six one- and two-joint muscles, reflexes, modeled control signals, muscle properties, and limb dynamics. First, we address the claim that “complex” equilibrium trajectories are required to account for nonmonotonic joint impedance patterns observed during multijoint movement. Using constant-rate shifts in the neurally specified equilibrium of the limb and constant cocontraction commands, we obtain patterns of predicted joint stiffness during simulated multijoint movements that match the nonmonotonic patterns reported empirically. We then use the algorithm proposed by Gomi and Kawato to compute a hypothetical equilibrium trajectory from simulated stiffness, viscosity, and limb kinematics. Like that reported by Gomi and Kawato, the resulting trajectory was nonmonotonic, first leading then lagging the position of the limb. Second, we address the claim that high levels of stiffness are required to generate rapid single-joint movements when simple equilibrium shifts are used. We compare empirical measurements of stiffness during rapid single-joint movements with the predicted stiffness of movements generated using constant-rate equilibrium shifts and constant cocontraction commands. Single-joint movements are simulated at a number of speeds, and the procedure used by Bennett to estimate stiffness is followed. We show that when the magnitude of the cocontraction command is scaled in proportion to movement speed, simulated joint stiffness varies with movement speed in a manner comparable with that reported by Bennett. Third, we address the related claim that nonmonotonic equilibrium shifts are required to generate rapid single-joint movements. Using constant-rate equilibrium shifts and constant cocontraction commands, rapid single-joint movements are simulated in the presence of external torques. We use the procedure reported by Latash and Gottlieb to compute hypothetical equilibrium trajectories from simulated torque and angle measurements during movement. As in Latash and Gottlieb, a nonmonotonic function is obtained even though the control signals used in the simulations are constant-rate changes in the equilibrium position of the limb. Differences between the “simple” equilibrium trajectory proposed in the present paper and those that are derived from the procedures used by Gomi and Kawato and Latash and Gottlieb arise from their use of simplified models of force generation.
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Gielen, C. C. A. M., E. J. Vrijenhoek, T. Flash i S. F. W. Neggers. "Arm Position Constraints During Pointing and Reaching in 3-D Space". Journal of Neurophysiology 78, nr 2 (1.08.1997): 660–73. http://dx.doi.org/10.1152/jn.1997.78.2.660.
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Gielen, C.C.A.M., E. J. Vrijenhoek, T. Flash, and S.F.W. Neggers. Arm position constraints during pointing and reaching in 3-D space. J. Neurophysiol. 78: 660–673, 1997. Arm movements in 3-D space were studied to investigate the reduction in the number of rotational degrees of freedom in the shoulder and elbow during pointing movements with the fully extended arm and during pointing movements to targets in various directions and at various distances relative to the shoulder, requiring flexion/extension in the elbow. The postures of both the upper arm and forearm can be described by rotation vectors, which represent these postures as a rotation from a reference position to the current position. The rotation vectors describing the posture of the upper arm and forearm were found to lie in a 2-D (curved) surface both for pointing with the fully extended arm and for pointing with elbow flexion. This result generalizes on previous results on the reduction of the number of degrees of freedom from three to two in the shoulder for the fully extended arm to a similar reduction in the number of degrees of freedom for the upper arm and forearm for normal arm movements involving also elbow flexion and extension. The orientation of the 2-D surface fitted to the rotation vectors describing the position of the upper arm and forearm was the same for pointing with the extended arm and for movements with flexion/extension of the elbow. The scatter in torsion of the rotation vectors describing the position of the upper arm and forearm relative to the 2-D surface was typically 3–4°, which is small considering the range of ∼180 and 360° for torsional rotations of the upper arm and the forearm, respectively. Donders' law states that arm posture for pointing to a target does not depend on previous positions of the arm. The results of our experiments demonstrate that the upper arm violates Donders' law. However, the variations in torsion of the upper arm are small, typically a few degrees. These deviations from Donders' law have been overlooked in previous studies, presumably because the variations are relatively small. These variations may explain the larger scatter of the rotation vectors for arm movements (3–4°) than reported for the eye (1°). Unlike for saccadic eye movements, joint rotations in the shoulder during aiming movements were not all single-axis rotations. On the contrary, the direction of the angular velocity vector varied during the movement in a consistent and reproducible way, depending on amplitude, direction, and starting position of the movement. These results reveal several differences between arm movements during pointing and saccadic eye movements. The implications for our understanding of the coordination of eye and arm movements and for the planning of 3-D arm movements are discussed.
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Mushiake, H., i P. L. Strick. "Pallidal neuron activity during sequential arm movements". Journal of Neurophysiology 74, nr 6 (1.12.1995): 2754–58. http://dx.doi.org/10.1152/jn.1995.74.6.2754.
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1. We examined the activity of neurons in the globus pallidus (GP) while monkeys (n = 2) performed sequential pointing movements under two task conditions: visually guided (TRACK task) and remembered (REM task). 2. Almost two-thirds of the task-related neurons in GP (155/236) were considered task dependent because they displayed exclusive or enhanced (greater than +/- 50%) changes in activity for one of the two task conditions. 3. More than 65% of the task-dependent neurons were termed REM neurons because they either displayed changes in activity that occurred only during the REM task or displayed changes that were more pronounced (greater than +/- 50%) during the REM task than during the TRACK task. 4. Nearly half of the REM neurons in GP displayed changes in activity that were limited to a single phase of the REM task (i.e., phase specific). Phase-specific neurons varied in the extent to which their activity depended on the particular sequence of movements performed. Some displayed a change in activity for all of the eight different movement sequences. Others displayed a change in activity during only one of the eight different sequences (i.e., phase and sequence specific). 5. We speculate that an ensemble of GP neurons with phase-specific responses could be used to encode the detailed spatio-temporal characteristics of a sequential movement. In this way, GP neurons would provide part of the neural substrate that solves the "serial order of motor behavior problem".
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Wei, Yuan, i Jing Zhao. "Designing Human-like Behaviors for Anthropomorphic Arm in Humanoid Robot NAO". Robotica 38, nr 7 (30.09.2019): 1205–26. http://dx.doi.org/10.1017/s026357471900136x.
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SUMMARYHuman-like motion of robots can improve human–robot interaction and increase the efficiency. In this paper, a novel human-like motion planning strategy is proposed to help anthropomorphic arms generate human-like movements accurately. The strategy consists of three parts: movement primitives, Bayesian network (BN), and a novel coupling neural network (CPNN). The movement primitives are used to decouple the human arm movements. The classification of arm movements improves the accuracy of human-like movements. The motion-decision algorithm based on BN is able to predict occurrence probabilities of the motions and choose appropriate mode of motion. Then, a novel CPNN is proposed to solve the inverse kinematics problems of anthropomorphic arms. The CPNN integrates different models into a single network and reflects the features of these models by changing the network structure. Through the strategy, the anthropomorphic arms can generate various human-like movements with satisfactory accuracy. Finally, the availability of the proposed strategy is verified by simulations for the general motion of humanoid NAO.
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Young, C. M., i R. H. Emson. "Rapid Arm Movements in Stalked Crinoids". Biological Bulletin 188, nr 1 (luty 1995): 89–97. http://dx.doi.org/10.2307/1542071.
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KASHIMA, Tadashi, i Yoshihisa ISURUGI. "Trajectory Formation in Human Arm Movements". Transactions of the Society of Instrument and Control Engineers 31, nr 9 (1995): 1416–22. http://dx.doi.org/10.9746/sicetr1965.31.1416.
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Billard, Aude, i Maja J. Matarić. "Learning human arm movements by imitation:". Robotics and Autonomous Systems 37, nr 2-3 (listopad 2001): 145–60. http://dx.doi.org/10.1016/s0921-8890(01)00155-5.
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Williamson, Matthew M. "Neural control of rhythmic arm movements". Neural Networks 11, nr 7-8 (październik 1998): 1379–94. http://dx.doi.org/10.1016/s0893-6080(98)00048-3.
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Waseem, Muhammad, Gerrard Devas i Emma Laureta. "A Neonate With Asymmetric Arm Movements". Pediatric Emergency Care 25, nr 2 (luty 2009): 98–99. http://dx.doi.org/10.1097/pec.0b013e318196fa82.
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von Hofsten, Claes, i Louise Ronnqvist. "The Structuring of Neonatal Arm Movements". Child Development 64, nr 4 (sierpień 1993): 1046. http://dx.doi.org/10.2307/1131326.
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Hatsopoulos, Nicholas G., i William H. Warren. "Resonance Tuning in Rhythmic Arm Movements". Journal of Motor Behavior 28, nr 1 (marzec 1996): 3–14. http://dx.doi.org/10.1080/00222895.1996.9941728.
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Hofsten, Claes, i Louise Ronnqvist. "The Structuring of Neonatal Arm Movements". Child Development 64, nr 4 (sierpień 1993): 1046–57. http://dx.doi.org/10.1111/j.1467-8624.1993.tb04187.x.
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Dounskaia, Natalia. "Kinematic invariants during cyclical arm movements". Biological Cybernetics 96, nr 2 (10.10.2006): 147–63. http://dx.doi.org/10.1007/s00422-006-0109-1.
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Corradini, M. L., M. Gentilucci, T. Leo i G. Rizzolatti. "Motor control of voluntary arm movements". Biological Cybernetics 67, nr 4 (sierpień 1992): 347–60. http://dx.doi.org/10.1007/bf02414890.
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Topka, H., Jürgen Konczak, Klaus Schneider, Andreas Boose i Johannes Dichgans. "Multijoint arm movements in cerebellar ataxia:". Experimental Brain Research 119, nr 4 (6.04.1998): 493–503. http://dx.doi.org/10.1007/s002210050365.
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Ma, S., i A. G. Feldman. "Two functionally different synergies during arm reaching movements involving the trunk". Journal of Neurophysiology 73, nr 5 (1.05.1995): 2120–22. http://dx.doi.org/10.1152/jn.1995.73.5.2120.
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1. To address the problem of the coordination of a redundant number of degrees of freedom in motor control, we analyzed the influence of voluntary trunk movements on the arm endpoint trajectory during reaching. 2. Subjects made fast noncorrected planar movements of the right arm from a near to a far target located in the ipsilateral work space at a 45 degrees angle to the sagittal midline of the trunk. These reaching movements were combined with a forward or a backward sagittal motion of the trunk. 3. The direction, positional error, curvature, and velocity profile of the endpoint trajectory remained invariant regardless of trunk movements. Trunk motion preceded endpoint motion by approximately 175 ms, continued during endpoint movement to the target, and outlasted it by 200 ms. This sequence of trunk and arm movements was observed regardless of the direction of the endpoint trajectory (to or from the far target) or trunk movements (forward or backward). 4. Our data imply that reaching movements result from two control synergies: one coordinates trunk and arm movements leaving the position of the endpoint unchanged, and the other produces interjoint coordination shifting the arm endpoint to the target. The use of functionally different synergies may underlie a solution of the redundancy problem.
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Flanders, Martha, Jan M. Hondzinski, John F. Soechting i Jadin C. Jackson. "Using Arm Configuration to Learn the Effects of Gyroscopes and Other Devices". Journal of Neurophysiology 89, nr 1 (1.01.2003): 450–59. http://dx.doi.org/10.1152/jn.00053.2002.
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Previous studies have perturbed the association between motor commands and arm movements by applying forces to the arm during two-dimensional movements. These studies have revealed that, when the normal hand path is perturbed, subjects gradually adapt their motor commands to return to this path. The present study used the spin of a gyroscope to create a complex perturbation, as subjects reached to targets presented in three dimensions. Hand path did not change, but the whole-arm geometry (“arm configuration” in four dimensions) was altered. Over a series of several hundred reaches to various targets, subjects gradually returned the arm movement to its normal configuration. Furthermore, during the course of this learning, subjects used a strategy that involved manipulating arm posture. A similar strategy was observed when subjects made reaching movements with a rod attached to the upper arm to change its inertial characteristics. In both cases, the gradual return to the normal arm movement was accomplished without an increase in kinetic energy, suggesting that arm postures and movements (kinematics) and muscular forces (kinetics) may be mutually optimized. In contrast to previous studies, the present results highlight the role of arm configuration (rather than hand path) in learning and control.
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Snyder, Lawrence H., Jeffrey L. Calton, Anthony R. Dickinson i Bonnie M. Lawrence. "Eye-Hand Coordination: Saccades Are Faster When Accompanied by a Coordinated Arm Movement". Journal of Neurophysiology 87, nr 5 (1.05.2002): 2279–86. http://dx.doi.org/10.1152/jn.00854.2001.
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When primates reach for an object, they very often direct an eye movement toward the object as well. This pattern of directing both eye and limb movements to the same object appears to be fundamental to eye-hand coordination. We investigated interactions between saccades and reaching movements in a rhesus monkey model system. The amplitude and peak velocity of isolated eye movements are positively correlated with one another. This relationship is called the main sequence. We now report that the main sequence relationship for saccades is changed during coordinated eye and arm movements. In particular, peak eye velocity is approximately 4% faster for the same size saccade when the saccade is accompanied by a coordinated arm movement. Saccade duration is reduced by an equivalent amount. The main sequence relationship is unperturbed when the arm moves simultaneously but in the opposite direction as the eyes, suggesting that eye and arm movements must be tightly coordinated to produce the effect. Candidate areas mediating this interaction include the posterior parietal cortex and the superior colliculus.
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Kalaska, John F. "The representation of arm movements in postcentral and parietal cortex". Canadian Journal of Physiology and Pharmacology 66, nr 4 (1.04.1988): 455–63. http://dx.doi.org/10.1139/y88-075.
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Considerable experimental evidence supports the hypothesis that the neocortical processes underlying kinesthetic sensation form a hierarchical series of cells signalling increasingly complex patterns of movement of the body. However, this view has been criticized and the data lack quantitative verification under controlled conditions. These studies have also typically used one-dimensional (reciprocal) movements, even of multiple degree-of-freedom joints such as the wrist or shoulder, and have been restricted to passive movements. This latter limitation is particularly critical, since the response of many muscle receptors is affected by fusimotor activity while that of many articular receptors is sensitive to the level of muscle contractile activity. Both factors introduce significant kinesthetic ambiguity to the signals arising from these receptors during active movement. This ambiguity is evident in the discharge of primary somatosensory cortex proprioceptive cells. Studies in area 5 show that single cells signal shoulder joint movements in the form of broad directional tuning curves. The pattern of activity of the entire population encodes movement direction. The cells appear to encode spatial aspects of movement unambiguously, since their discharge is relatively insensitive to the changes in muscle activity required to produce the same movements under different load conditions. It is not yet certain whether the somesthetic activity in area 5 is a kinesthetic representation that is sequential to and hierarchically superior to that in SI, or whether it is a parallel representation with separate and distinct functions.
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Lackner, J. R., i P. Dizio. "Rapid adaptation to Coriolis force perturbations of arm trajectory". Journal of Neurophysiology 72, nr 1 (1.07.1994): 299–313. http://dx.doi.org/10.1152/jn.1994.72.1.299.
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1. Forward reaching movements made during body rotation generate tangential Coriolis forces that are proportional to the cross product of the angular velocity of rotation and the linear velocity of the arm. Coriolis forces are inertial forces that do not involve mechanical contact. Virtually no constant centrifugal forces will be present in the background when motion of the arm generates transient Coriolis forces if the radius of body rotation is small. 2. We measured the trajectories of arm movements made in darkness to a visual target that was extinguished as movement began. The reaching movements were made prerotation, during rotation at 10 rpm in a fully enclosed rotating room, and postrotation. During testing the subject was seated at the center of the room and pointed radially. Neither visual nor tactile feedback about movement accuracy was present. 3. In experiment 1, subjects reached at a fast or slow rate and their hands made contact with a horizontal surface at the end of the reach. Their initial perrotary movements were highly significantly deviated relative to prerotation in both trajectories and end-points in the direction of the transient Coriolis forces that had been generated during the reaches. Despite the absence of visual and tactile feedback about reaching accuracy, all subjects rapidly regained straight movement trajectories and accurate endpoints. Postrotation, transient errors of opposite sign were present for both trajectories and endpoints. 4. In a second experiment the conditions were identical except that subjects pointed just above the location of the extinguished target so that no surface contact was involved. All subjects showed significant initial perrotation deviations of trajectories and endpoints in the direction of the transient Coriolis forces. With repeated reaches the trajectories, as viewed from above, again became straight, but there was only partial restoration of endpoint accuracy, so that subjects reached in a straight line to the wrong place. Aftereffects of opposite sign were transiently present in the postrotary movements. 5. These observations fail to support current equilibrium point models, both alpha and lambda, of movement control. Such theories would not predict endpoint errors under our experimental conditions, in which the Coriolis force is absent at the beginning and end of a movement. Our results indicate that detailed aspects of movement trajectory are being continuously monitored on the basis of proprioceptive feedback in relation to motor commands. Adaptive compensations can be initiated after one perturbation despite the absence of either visual or tactile feedback about movement trajectory and endpoint error. Moreover, movement trajectory and end-point can be remapped independently.(ABSTRACT TRUNCATED AT 400 WORDS)
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Hoffmann, Errol R., Alan H. S. Chan i P. T. Heung. "Head Rotation Movement Times". Human Factors: The Journal of the Human Factors and Ergonomics Society 59, nr 6 (24.03.2017): 986–94. http://dx.doi.org/10.1177/0018720817701000.
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Objective: The aim of this study was to measure head rotation movement times in a Fitts’ paradigm and to investigate the transition region from ballistic movements to visually controlled movements as the task index of difficulty (ID) increases. Background: For head rotation, there are gaps in the knowledge of the effects of movement amplitude and task difficulty around the critical transition region from ballistic movements to visually controlled movements. Method: Under the conditions of 11 ID values (from 1.0 to 6.0) and five movement amplitudes (20° to 60°), participants performed a head rotation task, and movement times were measured. Results: Both the movement amplitude and task difficulty have effects on movement times at low IDs, but movement times are dependent only on ID at higher ID values. Movement times of participants are higher than for arm/hand movements, for both ballistic and visually controlled movements. The information-processing rate of head rotational movements, at high ID values, is about half that of arm movements. Conclusion: As an input mode, head rotations are not as efficient as the arm system either in ability to use rapid ballistic movements or in the rate at which information may be processed. Application: The data of this study add to those in the review of Hoffmann for the critical IDs of different body motions. The data also allow design for the best arrangement of display that is under the design constraints of limited display area and difficulty of head-controlled movements in a data-inputting task.
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Colebatch, J. G., M. P. Deiber, R. E. Passingham, K. J. Friston i R. S. Frackowiak. "Regional cerebral blood flow during voluntary arm and hand movements in human subjects". Journal of Neurophysiology 65, nr 6 (1.06.1991): 1392–401. http://dx.doi.org/10.1152/jn.1991.65.6.1392.
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1. Regional cerebral blood flow (rCBF) was measured using positron emission tomography in six normal volunteers while at rest and while performing four different repetitive movements of the right arm. 2. The four movements were performed in random order and consisted of abduction of the index finger, making a fist, sequential thumb to digit opposition, and shoulder flexion. All the movements were done at the same rate, using an auditory cue and involved displacements through similar amounts of the physiological range at each joint. 3. Increases in rCBF were interpreted as evidence of local neural activation and all four movements were associated with significant increases in CBF in the contralateral sensorimotor and premotor areas and in the supplementary motor area (SMA). 4. The average increase in blood flow in the contralateral sensorimotor cortex was significantly greater for the shoulder movement (31%) than for the three other movements. The increases with finger opposition (21%) and fist-making (24%) were not significantly different, and both were significantly greater than with index finger movement (13%). These data indicate that neither "fractionation" nor distal movement per se cause selective activation of sensorimotor cortex. 5. Significantly greater increases in blood flow in both the contralateral premotor cortex and the SMA ("nonprimary motor areas") occurred with shoulder movement than with the other movements. Because this difference may be related to the significantly greater activation occurring concurrently in the sensorimotor cortex, this finding does not prove unequivocally a "selective" role of the nonprimary motor areas in proximal movement. 6. Neither of the two nonprimary motor areas showed selective activation when a simple sequence of finger movements was performed compared with repetitive contractions of the same fingers. 7. Shoulder movement alone was associated with significant increases in rCBF in the ipsilateral sensorimotor cortex (10%), the superior vermis of the cerebellum (19%), and Brodmann areas 5 and 40 in the contralateral hemisphere. 8. The average location of the center of excitation in the sensorimotor cortex and SMA differed for the four movements and was interpreted as evidence of within-limb somatotopy. The shoulder focus lay highest in the sensorimotor cortex and lowest in the SMA.
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Apker, Gregory A., Timothy K. Darling i Christopher A. Buneo. "Interacting Noise Sources Shape Patterns of Arm Movement Variability in Three-Dimensional Space". Journal of Neurophysiology 104, nr 5 (listopad 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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TATSUNO, Junya, Takefumi OSONE, Tomofumi NISHIDA i Hisato KOBAYASHI. "Trajectory Planning for Dual Arm Manipulator to Demonstrate Human Arm Movements". Japanese journal of ergonomics 39, nr 5 (2003): 201–9. http://dx.doi.org/10.5100/jje.39.201.
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Rushworth, M. F. S., H. Johansen-Berg i S. A. Young. "Parietal Cortex and Spatial-Postural Transformation During Arm Movements". Journal of Neurophysiology 79, nr 1 (1.01.1998): 478–82. http://dx.doi.org/10.1152/jn.1998.79.1.478.
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Rushworth, M.F.S., H. Johansen-Berg, and S. A. Young. Parietal cortex and spatial-postural transformation during arm movements. J. Neurophysiol. 79: 478–482, 1998. Cells in the parietal motor areas 5, MIP, and 7b have spatially tuned activity during movements. Lesions, however, do not disrupt visual reaching or learned nonspatial movement selection. The role of such parietal cells in sensorimotor coordinate transformations is unclear. The present experiment investigates whether the parietal motor areas are concerned with the following: 1) the transformation between the desired position in space of the hand and the limb's postural configuration during movement and 2) interjoint coordination. Six macaque monkeys were trained to reach in the dark. Spatial-postural transformations assume a simple form in the absence of vision and so may be most easily studied when animals reach in the dark. A lesion was placed in the parietal cortex that included areas 5, MIP, and 7b of three macaques. The simple relation between hand position and limb postural configuration seen in controls was disrupted after the lesion. The intercoordination of movements of the hand with those of the rest of the arm was also affected. The lesion did not affect the range or velocity of joint movements or the curvature of the hand's trajectory. The cell activity in parietal areas 5, MIP, and 7b may not be essential for the transformation between retinocentric representation of the target and shoulder centered representations of the desired position of the hand, but it is essential for both the subsequent transformation between desired hand position and the postural configuration of the arm and for interjoint integration.
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Apker, Gregory A., i Christopher A. Buneo. "Contribution of execution noise to arm movement variability in three-dimensional space". Journal of Neurophysiology 107, nr 1 (styczeń 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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Gdowski, Martha J., Lee E. Miller, Todd Parrish, Emmanuel K. Nenonene i James C. Houk. "Context Dependency in the Globus Pallidus Internal Segment During Targeted Arm Movements". Journal of Neurophysiology 85, nr 2 (1.02.2001): 998–1004. http://dx.doi.org/10.1152/jn.2001.85.2.998.
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Extracellular discharges from single neurons in the internal segment of the globus pallidus (GPi) were recorded and analyzed for rate changes associated with visually guided forearm rotations to four different targets. We sought to examine how GPi neurons contribute to movement preparation and execution. Unit discharge from 108 GPi neurons recorded in 35 electrode penetrations was aligned to the time of various behavioral events, including the onset of cued and return movements. In total, 39 of 108 GPi neurons (36%) were task-modulated, demonstrating statistically significant changes in discharge rate at various times between the presentation of visual cues and movement generation. Most often, strong modulation in discharge rate occurred selectively during either the cued ( n = 32) or return ( n = 2) phases of the task, although a few neurons ( n = 5) were well-modulated during both movement phases. Of the 34 neurons that were modulated exclusively during cued or return movements, 50% ( n = 17) were modulated similarly in association with movements to any target. The remaining 17 neurons exhibited considerable diversity in their discharge properties associated with movements to each target. Cued phases of behavior were always rewarded if executed correctly, whereas return phases were never rewarded. Overall, these data reveal that many GPi neurons discharged in a context-dependent manner, being modulated during cued, rewarded movements, but not during similar self-paced, unrewarded movements. When considered in the light of other observations, the context-dependence we have observed seems likely to be influenced by the animal's expectation of reward.
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Gottlieb, Gerald L., Qilai Song, Gil L. Almeida, Di-An Hong i Daniel Corcos. "Directional Control of Planar Human Arm Movement". Journal of Neurophysiology 78, nr 6 (1.12.1997): 2985–98. http://dx.doi.org/10.1152/jn.1997.78.6.2985.
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Gottlieb, Gerald L., Qilai Song, Gil L. Almeida, Di-an Hong, and Daniel Corcos. Directional control of planar human arm movement. J. Neurophysiol. 78: 2985–2998, 1997. We examined the patterns of joint kinematics and torques in two kinds of sagittal plane reaching movements. One consisted of movements from a fixed initial position with the arm partially outstretched, to different targets, equidistant from the initial position and located according to the hours of a clock. The other series added movements from different initial positions and directions and >40–80 cm distances. Dynamic muscle torque was calculated by inverse dynamic equations with the gravitational components removed. In making movements in almost every direction, the dynamic components of the muscle torques at both the elbow and shoulder were related almost linearly to each other. Both were similarly shaped, biphasic, almost synchronous and symmetrical pulses. These findings are consistent with our previously reported observations, which we termed a linear synergy. The relative scaling of the two joint torques changes continuously and regularly with movement direction. This was confirmed by calculating a vector defined by the dynamic components of the shoulder and elbow torques. The vector rotates smoothly about an ellipse in intrinsic, joint torque space as the direction of hand motion rotates about a circle in extrinsic Cartesian space. This confirms a second implication of linear synergy that the scaling constant between the linearly related joint torques is directionally dependent. Multiple linear regression showed that the torque at each joint scales as a simple linear function of the angular displacement at both joints, in spite of the complex nonlinear dynamics of multijoint movement. The coefficients of this function are independent of the initial arm position and movement distance and are the same for all subjects. This is an unanticipated finding. We discuss these observations in terms of the hypothesis that voluntary, multiple degrees of freedom, rapid reaching movements may use rule-based, feed-forward control of dynamic joint torque. Rule-based control of joint torque with separate dynamic and static controllers is an alternative to models such as those based on the equilibrium point hypotheses that rely on a positionally based controller to produce both dynamic and static torque components. It is also an alternative to feed-forward models that directly solve the problems of inverse dynamics. Our experimental findings are not necessarily incompatible with any of the alternative models, but they describe new, additional findings for which we need to account. The rules are chosen by the nervous system according to features of the kinematic task to couple muscle contraction at the shoulder and elbow in a linear synergy. Speed and load control preserves the relative magnitudes of the dynamic torques while directional control is accomplished by modulating them in a differential manner. This control system operates in parallel with a positional control system that solves the problems of postural stability.
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Cohen, D. A., M. J. Prud'homme i J. F. Kalaska. "Tactile activity in primate primary somatosensory cortex during active arm movements: correlation with receptive field properties". Journal of Neurophysiology 71, nr 1 (1.01.1994): 161–72. http://dx.doi.org/10.1152/jn.1994.71.1.161.
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1. Five hundred ninety-five single neurons with tactile receptive fields (RFs) on the contralateral arm were isolated in the primary somatosensory cortex (SI) of awake, behaving monkeys. 2. Fifty-eight percent of the tactile cells showed significantly different levels of activity during active movements of the arm in eight directions or during active maintenance of the arm over the target endpoints. 3. The discharge of many of the active tactile cells was unimodally tuned with movement direction and the pattern of the tactile population activity varied in a meaningful fashion with arm movement direction and posture. 4. The intensity of the arm-movement-induced activity was typically less than that evoked by direct tactile stimulation of the cell's RF. 5. The probability of task-related activity was correlated with certain RF properties, in particular the sensitivity of the cell to lateral stretch of the skin and to passive arm movements that avoided direct contact of the RF on any surface. 6. This suggests that task-related activity results mainly from the activation of tactile receptors by mechanical deformation of the skin as the arm changes geometry during movement. 7. These results demonstrate that tactile activity containing potential proprioceptive information is generated in SI during active arm movements that avoid direct contact of the skin with external surfaces. Whether or not this input contributes to the kinesthetic sensations evoked by the movements cannot be resolved by this study.
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ASFOUR, T., P. AZAD, F. GYARFAS i R. DILLMANN. "IMITATION LEARNING OF DUAL-ARM MANIPULATION TASKS IN HUMANOID ROBOTS". International Journal of Humanoid Robotics 05, nr 02 (czerwiec 2008): 183–202. http://dx.doi.org/10.1142/s0219843608001431.
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In this paper, we present an approach to imitation learning of arm movements in humanoid robots. Continuous hidden Markov models (HMMs) are used to generalize movements demonstrated to a robot multiple times. Characteristic features of the perceived movement, so-called key points, are detected in a preprocessing stage and used to train the HMMs. For the reproduction of a perceived movement, key points that are common to all (or almost all) demonstrations, so-called common key points, are used. These common key points are determined by comparing the HMM state sequences and selecting only those states that appear in every sequence. We also show how the HMM can be used to detect temporal dependencies between the two arms in dual-arm tasks. Experiments reported in this paper have been performed using a kinematics model of the human upper body to simulate the reproduction of arm movements and the generation of natural-looking joint configurations from perceived hand paths. Results are presented and discussed.
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Choi, Seung-Oh, Harry J. Meeuwsen i Robert W. Arnhold. "On the Psycho Physics of Arm-Positioning Movements". Perceptual and Motor Skills 80, nr 3_suppl (czerwiec 1995): 1163–69. http://dx.doi.org/10.2466/pms.1995.80.3c.1163.
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The basis for the relationship between physical stimulus and magnitude of psychological response in angular movements of the upper limbs was investigated. Participants compared movements to a standard location with movements to comparison locations and movements of a standard distance with movements of comparison distances. The results add to the controversy surrounding the explanations for the differences in psychological response magnitude of movements to locations and movements across distances. Data obtained from movements to locations and movements across distances indicated similar Weber ratios but different patterns for the just noticeable differences. The data of this and previous research suggest that the application of a prothetic continuum to arm movements is inappropriate. An alternative explanation of the differences in the perception of movements to locations and movements across distances is offered.
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Tao, Gordon, Aarlenne Z. Khan i Gunnar Blohm. "Corrective response times in a coordinated eye-head-arm countermanding task". Journal of Neurophysiology 119, nr 6 (1.06.2018): 2036–51. http://dx.doi.org/10.1152/jn.00460.2017.
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Inhibition of motor responses has been described as a race between two competing decision processes of motor initiation and inhibition, which manifest as the reaction time (RT) and the stop signal reaction time (SSRT); in the case where motor initiation wins out over inhibition, an erroneous movement occurs that usually needs to be corrected, leading to corrective response times (CRTs). Here we used a combined eye-head-arm movement countermanding task to investigate the mechanisms governing multiple effector coordination and the timing of corrective responses. We found a high degree of correlation between effector response times for RT, SSRT, and CRT, suggesting that decision processes are strongly dependent across effectors. To gain further insight into the mechanisms underlying CRTs, we tested multiple models to describe the distribution of RTs, SSRTs, and CRTs. The best-ranked model (according to 3 information criteria) extends the LATER race model governing RTs and SSRTs, whereby a second motor initiation process triggers the corrective response (CRT) only after the inhibition process completes in an expedited fashion. Our model suggests that the neural processing underpinning a failed decision has a residual effect on subsequent actions. NEW & NOTEWORTHY Failure to inhibit erroneous movements typically results in corrective movements. For coordinated eye-head-hand movements we show that corrective movements are only initiated after the erroneous movement cancellation signal has reached a decision threshold in an accelerated fashion.
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Laczko, Jozsef, Slobodan Jaric, Jozsef Tihanyi, Vladimir M. Zatsiorsky i Mark L. Latash. "Components of the End-Effector Jerk during Voluntary Arm Movements". Journal of Applied Biomechanics 16, nr 1 (luty 2000): 14–25. http://dx.doi.org/10.1123/jab.16.1.14.
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Jerk (time derivative of acceleration) of the endpoint of a multi-joint kinematic chain can be represented as the sum of terms related to jerks, accelerations, and velocities in individual joints. We investigated the relative contribution of these terms during simulations of planar movement of a 3-segment kinematic chain and also during unconstrained movements at different velocities, over different amplitudes, and with different intentionally changed curvature. Our results demonstrate that the term related to individual joint jerks dominates in the total endpoint jerk. This domination was particularly strong during voluntary movements and was not as striking during the simulations based on 5th-order polynomial functions for individual joint trajectories. Thus, the minimum-jerk criterion for multi-joint movements can be well approximated by minimization of the jerk-related terms for individual joints. The decomposition of endpoint jerk into its terms shows potential limitations of the commonly used 5th-order polynomial modeling for describing voluntary multi-joint movements.
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Sylos-Labini, Francesca, Yuri P. Ivanenko, Michael J. MacLellan, Germana Cappellini, Richard E. Poppele i Francesco Lacquaniti. "Locomotor-Like Leg Movements Evoked by Rhythmic Arm Movements in Humans". PLoS ONE 9, nr 3 (7.03.2014): e90775. http://dx.doi.org/10.1371/journal.pone.0090775.
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Graziano, Michael S. A., Tyson N. S. Aflalo i Dylan F. Cooke. "Arm Movements Evoked by Electrical Stimulation in the Motor Cortex of Monkeys". Journal of Neurophysiology 94, nr 6 (grudzień 2005): 4209–23. http://dx.doi.org/10.1152/jn.01303.2004.
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Electrical stimulation of the motor cortex in monkeys can evoke complex, multijoint movements including movements of the arm and hand. In this study, we examined these movements in detail and tested whether they showed adaptability to differing circumstances such as to a weight added to the hand. Electrical microstimulation was applied to motor cortex using pulse trains of 500-ms duration (matching the approximate duration of a reach). Arm movement was measured using a high-resolution three-dimensional tracking system. Movement latencies averaged 80.2 ms. Speed profiles were typically smooth and bell-shaped, and the peak speed covaried with movement distance. Stimulation generally evoked a specific final hand position. The convergence of the hand from disparate starting positions to a narrow range of final positions was statistically significant for every site tested (91/91). When a weight was fixed to the hand, for some stimulation sites (74%), the evoked movement appeared to compensate for the weight in that the hand was lifted to a similar final location. For other stimulation sites (26%), the weight caused a significant reduction in final hand height. For about one-half of the sites (54%), the variation in movement of each joint appeared to compensate for the variation in the other joints in a manner that stabilized the hand in a restricted region of space. These findings suggest that at least some of the stimulation-evoked movements reflect relatively high-level, adaptable motor plans.