Referent control of action and perception

Feldman, Anatol G.

doi:10.1007/978-1-4939-2736-4

Cited by 133 publications

(121 citation statements)

References 167 publications

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“…In that study, the authors used the idea that the neural control of movements can be adequately described as setting values (or time profiles) of spatial referent coordinates for the effectors (RC hypothesis, Latash 2010; Feldman 2015). Then, an apparently non-redundant task of producing a single pressing force with one fingertip appears redundant due to the possibility of changing RCs for agonist and antagonist muscle groups.…”

Section: Discussionmentioning

confidence: 99%

“…This view is based on the idea of movement control with RCs (Latash 2010; Feldman 2015) supplemented with an idea of RC-back-coupling. This latter idea assumes that, when a system is held by an external constraint at a coordinate that differs from its current RC, the RC starts to drift toward the actual coordinate.…”

Section: Discussionmentioning

confidence: 99%

“…In recent studies (Ambike et al 2015, 2016a), we have suggested a different conceptual framework to address the phenomena of unintentional changes in performance based on the idea of control of voluntary actions with referent coordinates (RCs) for the involved effectors (Latash 2010; Feldman 2015). According to this idea, the neural control of an action is associated with defining spatial RCs for the salient performance variable (Latash 2010; Feldman 2015).…”

Section: Introductionmentioning

confidence: 99%

“…According to this idea, the neural control of an action is associated with defining spatial RCs for the salient performance variable (Latash 2010; Feldman 2015). We view the drift in performance as a consequence of natural relaxation processes within the physical/physiological system involved in the action production, consistent with the system seeking a state with minimal potential energy.…”

Section: Introductionmentioning

confidence: 99%

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Unsteady steady-states: central causes of unintentional force drift

Ambike

Mattos²,

Zatsiorsky

et al. 2016

Exp Brain Res

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We applied the theory of synergies to analyze the processes that lead to unintentional decline in isometric fingertip force when visual feedback of the produced force is removed. We tracked the changes in hypothetical control variables involved in single fingertip force production based on the equilibrium-point hypothesis, namely, the fingertip referent coordinate (RFT) and its apparent stiffness (CFT). The system's state is defined by a point in the {RFT; CFT} space. We tested the hypothesis that, after visual feedback removal, this point (1) moves along directions leading to drop in the output fingertip force, and (2) has even greater motion along directions that leaves the force unchanged. Subjects produced a prescribed fingertip force using visual feedback, and attempted to maintain this force for 15 s after the feedback was removed. We used the “inverse piano” apparatus to apply small and smooth positional perturbations to fingers at various times after visual feedback removal. The time courses of RFT and CFT showed that force drop was mostly due to a drift in RFT towards the actual fingertip position. Three analysis techniques, namely, hyperbolic regression, surrogate data analysis, and computation of motor-equivalent and non-motor-equivalent motions, suggested strong co-variation in RFT and CFT stabilizing the force magnitude. Finally, the changes in the two hypothetical control variables {RFT; CFT} relative to their average trends also displayed covariation. On the whole the findings suggest that unintentional force drop is associated with (a) a slow drift of the referent coordinate that pulls the system towards a low-energy state, and (b) a faster synergic motion of RFT and CFT that tends to stabilize the output fingertip force about the slowly-drifting equilibrium point.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Unsteady steady-states: central causes of unintentional force drift

Ambike

Mattos²,

Zatsiorsky

et al. 2016

Exp Brain Res

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“…In our opinion, force tasks and kinematic tasks are both controlled by shifts in referent coordinates for the effectors and differ primarily in the external loading conditions (cf. Feldman 1986, 2015; Latash 2010). Hence, we think that the idea of a leading hand can be applied to two-hand kinetic tasks as supported by a recent study of two-hand and two-person accurate force production (Solnik et al 2015).…”

Section: Discussionmentioning

confidence: 99%

Analytical Inverse Optimization in Two-Hand Prehensile Tasks

Parsa

Ambike²,

Terekhov

et al. 2016

Journal of Motor Behavior

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We explored application of analytical inverse optimization (ANIO) method to the normal finger forces in unimanual and bimanual prehensile tasks with discrete and continuously changing constraints. The subjects held an instrumented handle vertically with one or two hands. The external torque and grip force changed across trials or within a trial continuously. Principal component analysis showed similar percentages of variance accounted for by the first two principal components across tasks and conditions. Compared to unimanual tasks, bimanual tasks showed significantly more frequent inability to find a cost function leading to a stable solution. In cases of stable solutions, similar second-order polynomials were computed as cost functions across tasks and condition. The bimanual tasks, however, showed significantly worse goodness-of-fit index values. We show that ANIO can be used in tasks with slowly changing constraints making it an attractive tool to study optimality of performance in special populations. We also show that ANIO can fail in multi-finger tasks, likely due to irreproducible behavior across trials, more likely to happen in bimanual tasks compared to unimanual tasks.

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Neuromechanical Circuits of the Spinal Motor Apparatus

Nichols

2024

Comprehensive Physiology

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The evolution of mechanisms for terrestrial locomotion has resulted in multi‐segmented limbs that allow navigation on irregular terrains, changing of direction, manipulation of external objects, and control over the mechanical properties of limbs important for interaction with the environment, with corresponding changes in neural pathways in the spinal cord. This article is focused on the organization of these pathways, their interactions with the musculoskeletal system, and the integration of these neuromechanical circuits with supraspinal mechanisms to control limb impedance. It is argued that neural pathways from muscle spindles and Golgi tendon organs form a distributive impedance controller in the spinal cord that controls limb impedance and coordination during responses to external disturbances. These pathways include both monosynaptic and polysynaptic components. Autogenic, monosynaptic pathways serve to control the spring‐like properties of muscles preserving the nonlinear relationship between stiffness and force. Intermuscular monosynaptic pathways compensate for inertial disparities between the inertial properties of limb segments and help to control inertial coupling between joints and axes of rotation. Reciprocal inhibition controls joint stiffness in conjunction with feedforward cocontraction commands. Excitatory force feedback becomes operational during locomotion and increases muscular stiffness to accommodate the higher inertial loads. Inhibitory force feedback is widely distributed among muscles. It is integrated with excitatory pathways from muscle spindles and Golgi tendon organs to determine limb stiffness and interjoint coordination during interactions with the environment. The intermuscular distribution of force feedback is variable and serves to modulate limb stiffness to meet the physical demands of different motor tasks. © 2024 American Physiological Society. Compr Physiol 14:5789‐5838, 2024.

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Referent control of action and perception

Cited by 133 publications

References 167 publications

Unsteady steady-states: central causes of unintentional force drift

Unsteady steady-states: central causes of unintentional force drift

Analytical Inverse Optimization in Two-Hand Prehensile Tasks

Neuromechanical Circuits of the Spinal Motor Apparatus

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