scholarly journals Should the Equilibrium Point Hypothesis (EPH) Be Considered a Scientific Theory?

Motor Control ◽  
2015 ◽  
Vol 19 (2) ◽  
pp. 142-148 ◽  
Author(s):  
Robert L. Sainburg
Keyword(s):  
Motor Control ◽  
Motor Neuron ◽  
Equilibrium Point ◽  
Scientific Theory ◽  
System Modeling ◽  
Central State ◽  
Equilibrium Point Hypothesis ◽  
Referent Configuration ◽  
Spinal Circuitry ◽  
Invariant Characteristic

The purpose of this commentary is to discuss factors that limit consideration of the equilibrium point hypothesis as a scientific theory. The EPH describes control of motor neuron threshold through the variable lambda, which corresponds to a unique referent configuration for a muscle, joint, or combination of joints. One of the most compelling features of the equilibrium point hypothesis is the integration of posture and movement control into a single mechanism. While the essential core of the hypothesis is based upon spinal circuitry interacting with peripheral mechanics, the proponents have extended the theory to include the higher-level processes that generate lambda, and in doing so, imposed an injunction against the supraspinal nervous system modeling, computing, or predicting dynamics. This limitation contradicts evidence that humans take account of body and environmental dynamics in motor selection, motor control, and motor adaptation processes. A number of unresolved limitations to the EPH have been debated in the literature for many years, including whether muscle resistance to displacement, measured during movement, is adequate to support this form of control, violations in equifinality predictions, spinal circuits that alter the proposed invariant characteristic for muscles, and limitations in the description of how the complexity of spinal circuitry might be integrated to yield a unique and stable equilibrium position for a given motor neuron threshold. In addition, an important empirical limitation of EPH is the measurement of the invariant characteristic, which needs to be done under a constant central state. While there is no question that the EPH is an elegant and generative hypothesis for motor control research, the claim that this hypothesis has reached the status of a scientific theory is premature.

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.

The Equilibrium Point Hypothesis and Its Application to Speech Motor Control

1996 ◽  
Vol 39 (2) ◽  
pp. 365-378 ◽  
Author(s):  
Pascal Perrier ◽  
David J. Ostry ◽  
Rafael Laboissière
Keyword(s):  
Motor Control ◽  
Equilibrium Point ◽  
Sagittal Plane ◽  
Muscle Properties ◽  
Equilibrium Point Hypothesis ◽  
Control Signals ◽  
Speech Control ◽  
Constant Magnitude ◽  
Speech Research ◽  
External Loads

In this paper, we address a number of issues in speech research in the context of the equilibrium point hypothesis of motor control. The hypothesis suggests that movements arise from shifts in the equilibrium position of the limb or the speech articulator. The equilibrium is a consequence of the interaction of central neural commands, reflex mechanisms, muscle properties, and external loads, but it is under the control of central neural commands. These commands act to shift the equilibrium via centrally specified signals acting at the level of the motoneurone (MN) pool. In the context of a model of sagittal plane jaw and hyoid motion based on the λ version of the equilibrium point hypothesis, we consider the implications of this hypothesis for the notion of articulatory targets. We suggest that simple linear control signals may underlie smooth articulatory trajectories. We explore as well the phenomenon of intra-articulator coarticulation in jaw movement. We suggest that even when no account is taken of upcoming context, that apparent anticipatory changes in movement amplitude and duration may arise due to dynamics. We also present a number of simulations that show in different ways how variability in measured kinematics can arise in spite of constant magnitude speech control signals.

On the Problem of Adequate Language in Motor Control

Motor Control ◽  
1998 ◽  
Vol 2 (4) ◽  
pp. 306-313 ◽  
Author(s):  
Israel M. Gelfand ◽  
Mark L. Latash
Keyword(s):  
Motor Control ◽  
Equilibrium Point ◽  
Voluntary Movement ◽  
Structural Units ◽  
Equilibrium Point Hypothesis

An adequate language is a prerequisite for progress in any area of science, including movement science. Notions of structural units and synergies and the principle of minimal interaction are revisited, discussed, and illustrated with a few examples from recent studies. Equilibrium-point hypothesis is considered an example of identifying significant variables in the control of a voluntary movement.

scholarly journals Motor control theories and their applications

Medicina ◽  
2010 ◽  
Vol 46 (6) ◽  
pp. 382 ◽  
Author(s):  
Mark Latash ◽  
Mindy Levin ◽  
John Scholz ◽  
Gregor Schöner
Keyword(s):  
Motor Control ◽  
Equilibrium Point ◽  
Movement Disorders ◽  
Stretch Reflex ◽  
Uncontrolled Manifold ◽  
Uncontrolled Manifold Hypothesis ◽  
Equilibrium Point Hypothesis ◽  
Performance Variables ◽  
Neural Computations ◽  
Technical Details

We describe several infl uential hypotheses in the field of motor control including the equilibrium-point (referent confi guration) hypothesis, the uncontrolled manifold hypothesis, and the idea of synergies based on the principle of motor abundance. The equilibrium-point hypothesis is based on the idea of control with thresholds for activation of neuronal pools; it provides a framework for analysis of both voluntary and involuntary movements. In particular, control of a single muscle can be adequately described with changes in the threshold of motor unit recruitment during slow muscle stretch (threshold of the tonic stretch reflex). Unlike the ideas of internal models, the equilibrium-point hypothesis does not assume neural computations of mechanical variables. The uncontrolled manifold hypothesis is based on the dynamic system approach to movements; it offers a toolbox to analyze synergic changes within redundant sets of elements related to stabilization of potentially important performance variables. The referent confi guration hypothesis and the principle of abundance can be naturally combined into a single coherent scheme of control of multi-element systems. A body of experimental data on healthy persons and patients with movement disorders are reviewed in support of the mentioned hypotheses. In particular, movement disorders associated with spasticity are considered as consequences of an impaired ability to shift threshold of the tonic stretch reflex within the whole normal range. Technical details and applications of the mentioned hypo theses to studies of motor learning are described. We view the mentioned hypotheses as the most promising ones in the field of motor control, based on a solid physical and neurophysiological foundation.

Recent Tests of the Equilibrium-Point Hypothesis (λ Model)

Motor Control ◽  
1998 ◽  
Vol 2 (3) ◽  
pp. 189-205 ◽  
Author(s):  
Anatol G. Feldman ◽  
David J. Ostry ◽  
Mindy F. Levin ◽  
Paul L. Gribble ◽  
Arnold B. Mitnitski
Keyword(s):  
Experimental Data ◽  
Motor Control ◽  
Equilibrium Point ◽  
Empirical Data ◽  
The Other ◽  
Logical System ◽  
Predictive Capacity ◽  
Equilibrium Point Hypothesis ◽  
Other Hand

The λ model of the equihbrium-point hypothesis (Feldman & Levin, 1995) is an approach to motor control which, like physics, is based on a logical system coordinating empirical data. The model has gone through an interesting period. On one hand, several nontrivial predictions of the model have been successfully verified in recent studies. In addition, the explanatory and predictive capacity of the model has been enhanced by its extension to multimuscle and multijoint systems. On the other hand, claims have recently appeared suggesting that the model should be abandoned. The present paper focuses on these claims and concludes that they are unfounded. Much of the experimental data that have been used to reject the model are actually consistent with it.

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 First validation of a novel assessgame quantifying selective voluntary motor control in children with upper motor neuron lesions

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Jeffrey W. Keller ◽  
Julia Balzer ◽  
Annina Fahr ◽  
Jan Lieber ◽  
Urs Keller ◽  
...  
Keyword(s):  
Motor Control ◽  
Motor Neuron ◽  
Low Cost ◽  
Compensatory Mechanisms ◽  
Involuntary Movements ◽  
Clinical Assessments ◽  
Voluntary Motor ◽  
Outcome Score ◽  
Computer Based ◽  
Neurologically Intact

AbstractThe question whether novel rehabilitation interventions can exploit restorative rather than compensatory mechanisms has gained momentum in recent years. Assessments measuring selective voluntary motor control could answer this question. However, while current clinical assessments are ordinal-scaled, which could affect their sensitivity, lab-based assessments are costly and time-consuming. We propose a novel, interval-scaled, computer-based assessment game using low-cost accelerometers to evaluate selective voluntary motor control. Participants steer an avatar owl on a star-studded path by moving the targeted joint of the upper or lower extremities. We calculate a target joint accuracy metric, and an outcome score for the frequency and amplitude of involuntary movements of adjacent and contralateral joints as well as the trunk. We detail the methods and, as a first proof of concept, relate the results of select children with upper motor neuron lesions (n = 48) to reference groups of neurologically intact children (n = 62) and adults (n = 64). Linear mixed models indicated that the cumulative therapist score, rating the degree of selectivity, was a good predictor of the involuntary movements outcome score. This highlights the validity of this assessgame approach to quantify selective voluntary motor control and warrants a more thorough exploration to quantify changes induced by restorative interventions.

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