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  1. Action and attention.A. H. C. Van der Heijden & Bruce Bridgeman - 1994 - Behavioral and Brain Sciences 17 (2):225-226.
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  • Moving beyond imagination.Robert Dufour, Martin H. Fischer & David A. Rosenbaum - 1994 - Behavioral and Brain Sciences 17 (2):206-207.
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  • Visual-spatial movement goals.Digby Elliott & Brian K. V. Maraj - 1994 - Behavioral and Brain Sciences 17 (2):207-207.
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  • Motor models as steps to higher cognition.Rick Grush - 1994 - Behavioral and Brain Sciences 17 (2):209-210.
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  • Motor simulation.Adam Morton - 1994 - Behavioral and Brain Sciences 17 (2):215-215.
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  • The representing brain: Neural correlates of motor intention and imagery.Marc Jeannerod - 1994 - Behavioral and Brain Sciences 17 (2):187-202.
    This paper concerns how motor actions are neurally represented and coded. Action planning and motor preparation can be studied using a specific type of representational activity, motor imagery. A close functional equivalence between motor imagery and motor preparation is suggested by the positive effects of imagining movements on motor learning, the similarity between the neural structures involved, and the similar physiological correlates observed in both imaging and preparing. The content of motor representations can be inferred from motor images at a (...)
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  • Levers to generate movement.U. Windhorst - 1995 - Behavioral and Brain Sciences 18 (4):784-785.
    The following questions are discussed: (1) Who determines the nature of “control variables”? (2) Is the “positional monopoly” healthy? (3) Does a descending command alter reflex threshold alone without eoncomitantly altering stiffness? (4) How does the CNS deal with history-dependent effects? (5) Should we abandon the idea that the CNS controls classical Newtonian variables such as muscle length?
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  • Two joints are more than twice one joint.Jeroen B. J. Smeets - 1995 - Behavioral and Brain Sciences 18 (4):779-780.
    An alternative multi-joint extension to the lambda model is proposed. According to this extension, the activity of a muscle depends not only on the difference between lambda and length of that muscle, but also on the difference between lambda and length of other muscles. This 2-D extension can describe more neurophysiological experiments than the extension proposed in the target article.
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  • Control parameters, equilibria, and coordination dynamics.Dagmar Sternad & M. T. Turvey - 1995 - Behavioral and Brain Sciences 18 (4):780-780.
    Important similarities exist between the dynamical concepts implicit in Feldman & Levin's extended λ model and those basic to a dynamical systems approach. We argue that careful application of the key concepts of control and order parameters, equilibria, and stability, can relate known facts of neuromuscular processes to the observables of functional, task-specific behavior.
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  • Do control variables exist?Nicholas G. Hatsopoulos & William H. Warren - 1995 - Behavioral and Brain Sciences 18 (4):762-762.
    We argue that the concept of a control variable (CV) as described by Feldman and Levin needs to be revised because it does not account for the influence of sensory feedback from the periphery. We provide evidence from the realm of rhythmic movements that sensory feedback can permanently alter the frequency and phase of a centrally generated rhythm.
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  • The unobservability of central commands: Why testing hypotheses is so difficult.Antony Hodgson - 1995 - Behavioral and Brain Sciences 18 (4):763-764.
    The experiments Feldman and Levin suggest do not definitively test their proposed solution to the problem of selecting muscle activations. Their test of the movement directions that elicit EMG activity can be interpreted without regard to the form of the central commands, and their fast elbow flexion test is based on a forward computation that obscures the insensitivity of the predicted trajectory to the details of the putative commands.
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  • Neurophysiology of preparation, movement and imagery.Jerome N. Sanes - 1994 - Behavioral and Brain Sciences 17 (2):221-223.
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  • Can the λ model be used to interpret the activity of single neurons?Stephen H. Scott - 1995 - Behavioral and Brain Sciences 18 (4):778-779.
    Whereas the λ model provides a useful technique to describe complex movements, the focus on control variables in this model limits its potential for interpreting the activity and function of many cells in motor areas of the CNS.
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  • Frames of reference interact and are task-dependent.Bruce A. Kay - 1995 - Behavioral and Brain Sciences 18 (4):765-765.
    The problem for the CNS in any particular movement task is to coordinate the various frames of reference appropriate to the task. Control variables are determined by this coordination. The coordination problem varies greatly from task to task, and so no single set of control variables is likely to account for a broad range of movement tasks.
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  • Equilibrium-point control? Yes! Deterministic mechanisms of control? No!Mark L. Latash - 1995 - Behavioral and Brain Sciences 18 (4):765-766.
    The equilibrium-point hypothesis (the λ-model) is superior to all other models of single-joint control and provides deep insights into the mechanisms of control of multi-joint movements. Attempts at associating control variables with neurophysiological variables look confusing rather than promising. Probabilistic mechanisms may play an important role in movement generation in redundant systems.
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  • Reciprocal and coactivation commands are not sufficient to describe muscle activation patterns.C. C. A. M. Gielen & B. van Bolhuis - 1995 - Behavioral and Brain Sciences 18 (4):754-755.
    Recent results have shown that the relative activation of muscles is different for isometric contractions and for movements. These results exclude an explanation of muscle activation patterns by a combination ofreciprocal and coactivation commands. These results also indicate that joint stiffness is not uniquely determined and that it may be different for isometric contractions and movements.
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  • Is λ an appropriate control variable for locomotion?Thomas M. Hamm & Zong-Sheng Han - 1995 - Behavioral and Brain Sciences 18 (4):761-762.
    The lambda model predicts that the command received by each motor nucleus during locomotion is specific for the joint at which its muscle acts and is independent of external conditions. However, investigation of the commands received by motor nuclei during fictive locomotion and of the sensitivity of these commands to feedback from the limb during locomotion indicates that neither condition is satisfied.
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  • Natural unconstrained movements obey rules different from constrained elementary movements.Michel Desmurget, Yves Rossetti & Claude Prablanc - 1995 - Behavioral and Brain Sciences 18 (4):750-750.
    The concept of a conservative control strategy minimizing the number of degrees of freedom used is criticised with reference to 3-D simple reaching and grasping experiments. The vector error in a redundant system would not be the prime controlled variable, but rather the posture for reaching, as exemplified by nearly straight displacements in joint space as opposed to curved ones in task space.
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  • The λ model for motor control: More than meets the eye.Mindy F. Levin & Anatol G. Feldman - 1995 - Behavioral and Brain Sciences 18 (4):786-806.
    Understanding of the λ model has greatly increased in recent years as evidenced by most of the commentaries. Some commentators underscored the potential of the model to integrate aspects of different sensorimotor systems in the production of movement. Other commentators focused on not-yet-fully-developed parts of the model. A few persisted in misunderstanding some of its basic concepts, and on these grounds they reject it. In responding to commentaries we continue to elaborate on some fundamental points of the model, especially control (...)
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  • Interneurons as backseat drivers and the elusive control variable.T. Richard Nichols - 1995 - Behavioral and Brain Sciences 18 (4):772-773.
    It is proposed here that the spinal network of proprioceptive feedback from length and force receptors constitutes the mechanism underlying the coordination of activation thresholds for muscles acting about the same and neighboring joints. For the most part, these circuits come between motoneurons and supraspinal signals, invalidating the idea that the activation thresholds constitute control variables for the motor system.
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  • Command invariants and the frame of reference for human movement.David J. Ostry, Rafael Laboissière & Paul L. Gribble - 1995 - Behavioral and Brain Sciences 18 (4):770-772.
    We describe a solution to the redundancy problem related to that proposed in Feldman & Levin's target article. We suggest that the system may use a fixed mapping between commands organized at the level of degrees of freedom and commands to individual muscles. This proposal eliminates the need to maintain an explicit representation of musculoskeletalgeometry in planning movements.
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  • Inverse kinematic problem: Solutions by pseudoinversion, inversion and no-inversion.Simon R. Goodman - 1995 - Behavioral and Brain Sciences 18 (4):756-758.
    Kinematic properties of reaching movements reflect constraints imposed on the joint angles. Contemporary models present solutions to the redundancy problem by a pseudoinverse procedure (Whitney 1969) or without any inversion (Berkenblit et al. 1986). Feldman & Levin suggest a procedure based on a regular inversion. These procedures are considered as an outcome of a more general approach.
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  • Conservative or nonconservative control schemes.Daniel M. Corcos & Kerstin Pfann - 1995 - Behavioral and Brain Sciences 18 (4):747-749.
    The conservative strategy proposed by the authors suggests a solution of the degrees-of-freedom problem of the controller. However, several simple motor control tasks cannot be explained by this strategy. A nonconservative strategy, in which more parameters of the control signal vary, can account for these simple motor tasks. However, the simplicity that distinguishes the proposed model from many others is lost.
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  • Grip force adjustments during rapid hand movements suggest that detailed movement kinematics are predicted.J. Randall Flanagan, James R. Tresilian & Alan M. Wing - 1995 - Behavioral and Brain Sciences 18 (4):753-754.
    The λ model suggests that detailed kinematics arise from changes in control variables and need not be explicitly planned. However, we have shown that when moving a grasped object, grip force is precisely modulated in phase with acceleration-dependent inertial load. This suggests that the motor system can predict detailed kinematics. This prediction may be based on a forward model of the dynamics of the loaded limb.
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  • Representations of movement and representations in movement.Giuseppe Pellizzer & Apostolos P. Georgopoulos - 1994 - Behavioral and Brain Sciences 17 (2):216-217.
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  • Motor images are action plans.Wolfgang Prinz - 1994 - Behavioral and Brain Sciences 17 (2):218-218.
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  • Kinaesthetic illusions as tools in understanding motor imagery.J. P. Roll, J. C. Gilhodes & R. Roll - 1994 - Behavioral and Brain Sciences 17 (2):220-221.
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  • Do object affordances represent the functionality of an object?Ruzena Bajcsy - 1994 - Behavioral and Brain Sciences 17 (2):202-202.
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  • On the relation between motor imagery and visual imagery.Roberta L. Klatzky - 1994 - Behavioral and Brain Sciences 17 (2):212-213.
    Jeannerod's target article describes support, through empirical and neurological findings, for the intriguing idea of motor imagery, a form of representation hypothesized to have levels of functional equivalence with motor preparation, while being consciously accessible. Jeannerod suggests that the subjectively accessible content of motor imagery allows it to be distinguished from motor preparation, which is unconscious. Motor imagery is distinguished from visual imagery in terms of content. Motor images are kinesthetic in nature; they are parametrized by variables such as force (...)
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  • Kinematic invariances and body schema.Pietro Morasso & Vittorio Sanguineti - 1995 - Behavioral and Brain Sciences 18 (4):769-770.
    Generalizing the notion that muscles are positional frames of reference, a high-dimensional muscle space is defined for multi-muscle systems with an embedded low-dimensional motor manifold of functional articulators. A central representation of such a manifold is proposed as computational body schema. The example of the jaw-tongue system is presented, discussing the relation of functional articulators with kinematic invariances and control problems.
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  • The case of the missing CVs: Multi-joint primitives.Simon Giszter - 1995 - Behavioral and Brain Sciences 18 (4):755-756.
    The search for simplifying principles in motor control motivates the target article. One method that the CNS uses to simplify the task of controlling a limb's mechanical properties is absent from the article. Evidence from multi-joint, force-field measurements and from kinematics that points to the existence of multi-joint primitives as control variables is discussed.
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  • The lambda model is only one piece in the motor control puzzle.Jeffrey Dean - 1995 - Behavioral and Brain Sciences 18 (4):749-749.
    The lambda model provides a physiologically grounded terminology for describing muscle function and emphasizes the important influence of environmental and reflex-mediated effects on final states. However, lambda itself is only a convenient point on the length-tension curve; its importance should not be overemphasized. Ascribing movement to changes in a lambda-based frame of reference is generally valid, but it leaves unanswered a number of questions concerning mechanisms.
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  • Biological variability and control of movements via δλ.Charles E. Wright & Rebecca A. States - 1995 - Behavioral and Brain Sciences 18 (4):786-786.
    Three issues related to Feldman and Levin's treatment of biological variability are discussed. We question the usefulness of the indirect component of δλ. We suggest that trade-offs between speed and accuracy in aimed movements support identification of δλ, rather than λ, as a control variable. We take issue with the authors' proposal for resolving redundancy in multi-joint movements, given recent data.
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  • How far should we extend the equilibrium point (lambda) hypothesis?Jack M. Winters - 1995 - Behavioral and Brain Sciences 18 (4):785-786.
    A key feature of the lambda model is the hypothesis of a local spring-like muscle-reflex system defined by a central control variable that has units of position. This is intriguing, especially for a study of postural stability in large-scale systems, but it has limited direct application to skilled everyday movements. If movement is considered as a goal-directed, neuro-optimization problem, however, theavailabilityof lambda-like peripheral models (vs. conventional musculoskeletal models) deserves exploration.
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  • The mystery-mastery-imagery complex.H. T. A. Whiting & R. P. Ingvaldsen - 1994 - Behavioral and Brain Sciences 17 (2):228-229.
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  • Potential disparities between imagining and preparing motor skills.Charles B. Walter & Stephan P. Swinnen - 1994 - Behavioral and Brain Sciences 17 (2):227-228.
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  • Imagery needs preparation too.Stefan Vogt - 1994 - Behavioral and Brain Sciences 17 (2):226-227.
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  • Equifinality and phase-resetting: The role of control parameter manipulations.R. E. A. van Emmerik & R. C. Wagenaar - 1995 - Behavioral and Brain Sciences 18 (4):783-784.
    It is argued that the equilibrium point model can lead to new insights regarding transition and stability processes in movement coordination. The role of movement control parameters on equifinality and phase-resetting is discussed; not only control but also external control parameters can affect the global dynamical regime.
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  • Canonical representations and constructive praxis: Some developmental and linguistic considerations.Chris Sinha - 1994 - Behavioral and Brain Sciences 17 (2):223-224.
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  • Involvement of primary motor cortex in motor imagery and mental practice.Mark Hallett, Jordan Fieldman, Leonardo G. Cohen, Norihiro Sadato & Alvaro Pascual-Leone - 1994 - Behavioral and Brain Sciences 17 (2):210-210.
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  • Nonconscious motor images.Giacomo Rizzolatti - 1994 - Behavioral and Brain Sciences 17 (2):220-220.
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  • On the limitations of imaging imagining.Christopher A. Buneo & Martha Flanders - 1994 - Behavioral and Brain Sciences 17 (2):202-203.
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  • The origin and use of positional frames of reference in motor control.Anatol G. Feldman & Mindy F. Levin - 1995 - Behavioral and Brain Sciences 18 (4):723-744.
    A hypothesis about sensorimotor integration (the λ model) is described and applied to movement control and kinesthesia. The central idea is that the nervous system organizes positional frames of reference for the sensorimotor apparatus and produces active movements by shifting the frames in terms of spatial coordinates. Kinematic and electromyographic patterns are not programmed, but emerge from the dynamic interaction among the system s components, including external forces within the designated frame of reference. Motoneuronal threshold properties and proprioceptive inputs to (...)
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  • Origins of origins of motor control.Esther Thelen - 1995 - Behavioral and Brain Sciences 18 (4):780-783.
    Examination of infant spontaneous and goal-directed arm movements supports Feldman and Levin's hypothesis of a functional hierarchy. Early infant movements are dominated by biomechanical and dynamic factors without external frames of reference. Development involves not only learning to generate these frames of reference, but also protecting the higher-level goal of the movement from internal and external perturbations.
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  • Separability of reference frame distinctions from motor and visual images.Gary W. Strong - 1994 - Behavioral and Brain Sciences 17 (2):224-225.
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  • How do we satisfy our goals?Paul G. Skokowski - 1994 - Behavioral and Brain Sciences 17 (2):224-224.
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  • To dream is not to (intend to) do.Jean Requin - 1994 - Behavioral and Brain Sciences 17 (2):218-219.
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  • Position is everything?Karl H. Pribram - 1995 - Behavioral and Brain Sciences 18 (4):776-778.
    Neurophysiological evidence consonant with F&L's lambda model is reviewed and results of additional experiments are presented. The evidence shows that there are neurons in the motor cortex that respond to selective band widths of passive sinusoidal movements; the additional data show how, with movement, directionally sensitive population vectors can be shown to emerge from the data.
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  • The λ model: Can it walk?Aftab E. Patla - 1995 - Behavioral and Brain Sciences 18 (4):775-776.
    Generation of swing phase limb trajectory over obstacles during locomotion should be a reasonable test for the λ model proposed by Feldman and Levin. The observed features such as lack of simple amplitude scaling of endpoint (toe) trajectories for different obstacle heights, complex shaped toe velocity profiles, and exploitation of passive intersegmental dynamics to control limb elevation cannot be adequately explained by the λ model.
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  • Let us accept a “controlled trade-off” model of motor control.Lloyd D. Partridge - 1995 - Behavioral and Brain Sciences 18 (4):773-775.
    The trade-off between force and length of muscle as adjusted by neural signals is a critical fact in the dynamics of motor control. Whether we call it “length-tension effect,” “feedback-like,” “invariant condition,” or “spring-like” is unimportant. We must not let semantics or details of representation obscure the basic physics of effects introduced by this trade-off in muscle.
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