Equilibrium-Point Hypothesis

2016 ◽  
pp. 247-273
Author(s):  
Mark L. Latash ◽  
Vladimir M. Zatsiorsky
Keyword(s):  
Equilibrium Point ◽  
Equilibrium Point Hypothesis

scholarly journals Synergies in the space of control variables within the equilibrium-point hypothesis

Neuroscience ◽  
2016 ◽  
Vol 315 ◽  
pp. 150-161 ◽  
Author(s):  
S. Ambike ◽  
D. Mattos ◽  
V.M. Zatsiorsky ◽  
M.L. Latash
Keyword(s):  
Equilibrium Point ◽  
Control Variables ◽  
Equilibrium Point Hypothesis

scholarly journals Case Studies in Neuroscience: The central and somatosensory contributions to finger interdependence and coordination: lessons from a study of a “deafferented person”

2019 ◽  
Vol 121 (6) ◽  
pp. 2083-2087 ◽  
Author(s):  
Cristian Cuadra ◽  
Ali Falaki ◽  
Robert Sainburg ◽  
Fabrice R. Sarlegna ◽  
Mark L. Latash
Keyword(s):  
Peripheral Neuropathy ◽  
Equilibrium Point ◽  
Force Production ◽  
Total Force ◽  
Equilibrium Point Hypothesis ◽  
Somatosensory Feedback ◽  
Central Origin ◽  
Neural Origin ◽  
Zero Values ◽  
Large Fiber

We tested finger force interdependence and multifinger force-stabilizing synergies in a patient with large-fiber peripheral neuropathy (“deafferented person”). The subject performed a range of tasks involving accurate force production with one finger and with four fingers. In one-finger tasks, nontask fingers showed unintentional force production (enslaving) with an atypical pattern: very large indices for the lateral (index and little) fingers and relatively small indices for the central (middle and ring) fingers. Indices of multifinger synergies stabilizing total force and of anticipatory synergy adjustments in preparation to quick force pulses were similar to those in age-matched control females. During constant force production, removing visual feedback led to a slow force drift to lower values (by ~25% over 15 s). The results support the idea of a neural origin of enslaving and suggest that the patterns observed in the deafferented person were reorganized based on everyday manipulation tasks. The lack of significant changes in the synergy index shows that synergic control can be organized in the absence of somatosensory feedback. We discuss the control of the hand in deafferented persons within the α-model of the equilibrium-point hypothesis and suggest that force drift results from an unintentional drift of the control variables to muscles toward zero values. NEW & NOTEWORTHY We demonstrate atypical patterns of finger enslaving and unchanged force-stabilizing synergies in a person with large-fiber peripheral neuropathy. The results speak strongly in favor of central origin of enslaving and its reorganization based on everyday manipulation tasks. The data show that synergic control can be implemented in the absence of somatosensory feedback. We discuss the control of the hand in deafferented persons within the α-model of the equilibrium-point hypothesis.

scholarly journals Evolution of Motor Control: From Reflexes and Motor Programs to the Equilibrium-Point Hypothesis

2008 ◽  
Vol 19 (1) ◽  
pp. 3-24 ◽  
Author(s):  
Mark Latash
Keyword(s):  
Motor Control ◽  
Equilibrium Point ◽  
Voluntary Movements ◽  
Motor Programs ◽  
Equilibrium Point Hypothesis ◽  
Motor Synergies ◽  
Recent Developments ◽  
Active Motor ◽  
Control Theories

Evolution of Motor Control: From Reflexes and Motor Programs to the Equilibrium-Point HypothesisThis brief review analyzes the evolution of motor control theories along two lines that emphasize active (motor programs) and reactive (reflexes) features of voluntary movements. It suggests that the only contemporary hypothesis that integrates both approaches in a fruitful way is the equilibrium-point hypothesis. Physical, physiological, and behavioral foundations of the EP-hypothesis are considered as well as relations between the EP-hypothesis and the recent developments of the notion of motor synergies. The paper ends with a brief review of the criticisms of the EP-hypothesis and challenges that the hypothesis faces at this time.

scholarly journals Hip retraction enhances walking stability on a ramp: an equilibrium point hypothesis-based study

2019 ◽  
Author(s):  
Alireza Bahramian ◽  
Elham Shamsi ◽  
Farzad Towhidkhah ◽  
Sajad Jafari
Keyword(s):  
Equilibrium Point ◽  
Equilibrium Points ◽  
Human Motion ◽  
Body Motion ◽  
Equilibrium Point Hypothesis ◽  
The Central Nervous System ◽  
Natural Response ◽  
External Forces ◽  
Positive Effect ◽  
Body Joint

AbstractHip retraction is a phenomenon observed in human walking. The swing leg rotates backward at the end of the motion. Its positive effect on motion stability was reported in the literature based on some simple models for running or walking. In this study, it is shown that hip retraction angle increases in humans during their ascending and descending walk on a stair. In previous studies, hip retraction was modeled by defining a proper motion for the swing leg. According to the equilibrium point hypothesis, the central nervous system (CNS) defines only the equilibrium point(s) and stiffness(es) for body joint(s) to control the human motion. Human body motion emerges as its natural response as a result of the external forces and the defined equilibrium points of joints. Considering the hip torque as a spring-like model with an equilibrium point and stiffness, this study revealed that the hip retraction can be generated by the natural response of the swing leg. Besides, the stabilizing effect of hip retraction was demonstrated by a model for human’s ascending and descending walking on a ramp with a range of positive and negative angles, respectively. The findings suggest that the CNS needs to define equilibrium point just ahead of the stance leg to take advantage of the hip retraction effect on ascending and descending walks on a ramp.

scholarly journals A Vexing Question in Motor Control: The Degrees of Freedom Problem

2022 ◽  
Vol 9 ◽  
Author(s):  
Pietro Morasso
Keyword(s):  
Nervous System ◽  
Equilibrium Point ◽  
Degrees Of Freedom ◽  
Optimal Solution ◽  
Motor Units ◽  
Point Of View ◽  
Uncontrolled Manifold ◽  
Muscle Synergy ◽  
Equilibrium Point Hypothesis ◽  
Daily Life Activities

The human “marionette” is extremely complex and multi-articulated: anatomical redundancy (in terms of Degrees of Freedom: DoFs), kinematic redundancy (movements can have different trajectories, velocities, and accelerations and yet achieve the same goal, according to the principle of Motor Equivalence), and neurophysiological redundancy (many more muscles than DoFs and multiple motor units for each muscle). Although it is quite obvious that such abundance is not noxious at all because, in contrast, it is instrumental for motor learning, allowing the nervous system to “explore” the space of feasible actions before settling on an elegant and possibly optimal solution, the crucial question then boils down to figure out how the nervous system “chooses/selects/recruits/modulates” task-dependent subsets of countless assemblies of DoFs as functional motor synergies. Despite this daunting conceptual riddle, human purposive behavior in daily life activities is a proof of concept that solutions can be found easily and quickly by the embodied brain of the human cognitive agent. The point of view suggested in this essay is to frame the question above in the old-fashioned but still seminal observation by Marr and Poggio that cognitive agents should be regarded as Generalized Information Processing Systems (GIPS) and should be investigated according to three nearly independent but complementary levels of analysis: 1) the computational level, 2) the algorithmic level, and 3) the implementation level. In this framework, we attempt to discriminate as well as aggregate the different hypotheses and solutions proposed so far: the optimal control hypothesis, the muscle synergy hypothesis, the equilibrium point hypothesis, or the uncontrolled manifold hypothesis, to mention the most popular ones. The proposed GIPS follows the strategy of factoring out shaping and timing by adopting a force-field based approach (the Passive Motion Paradigm) that is inspired by the Equilibrium Point Hypothesis, extended in such a way to represent covert as well overt actions. In particular, it is shown how this approach can explain spatio-temporal invariances and, at the same time, solve the Degrees of Freedom Problem.

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