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.

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.

New Advanced Strategies for the Treatment of Lysosomal Diseases Affecting the Central Nervous System

2019 ◽  
Vol 25 (17) ◽  
pp. 1933-1950 ◽  
Author(s):  
Maria R. Gigliobianco ◽  
Piera Di Martino ◽  
Siyuan Deng ◽  
Cristina Casadidio ◽  
Roberta Censi
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Polymeric Nanoparticles ◽  
Genetic Diseases ◽  
Point Of View ◽  
Lysosomal Storage ◽  
Enzyme Replacement ◽  
Lysosomal Diseases ◽  
The Central Nervous System ◽  
Enzyme Delivery

Lysosomal Storage Disorders (LSDs), also known as lysosomal diseases (LDs) are a group of serious genetic diseases characterized by not only the accumulation of non-catabolized compounds in the lysosomes due to the deficiency of specific enzymes which usually eliminate these compounds, but also by trafficking, calcium changes and acidification. LDs mainly affect the central nervous system (CNS), which is difficult to reach for drugs and biological molecules due to the presence of the blood-brain barrier (BBB). While some therapies have proven highly effective in treating peripheral disorders in LD patients, they fail to overcome the BBB. Researchers have developed many strategies to circumvent this problem, for example, by creating carriers for enzyme delivery, which improve the enzyme’s half-life and the overexpression of receptors and transporters in the luminal or abluminal membranes of the BBB. This review aims to successfully examine the strategies developed during the last decade for the treatment of LDs, which mainly affect the CNS. Among the LD treatments, enzyme-replacement therapy (ERT) and gene therapy have proven effective, while nanoparticle, fusion protein, and small molecule-based therapies seem to offer considerable promise to treat the CNS pathology. This work also analyzed the challenges of the study to design new drug delivery systems for the effective treatment of LDs. Polymeric nanoparticles and liposomes are explored from their technological point of view and for the most relevant preclinical studies showing that they are excellent choices to protect active molecules and transport them through the BBB to target specific brain substrates for the treatment of LDs.

Does the nervous system use equilibrium-point control to guide single and multiple joint movements?

1992 ◽  
Vol 15 (04) ◽  
pp. 603-613 ◽  
Author(s):  
E. Bizzi ◽  
N. Hogan ◽  
F. A. Mussa-Ivaldi ◽  
S. Giszter
Keyword(s):  
Nervous System ◽  
Equilibrium Point ◽  
System Use ◽  
Point Control

scholarly journals From Loschmidt daemons to time-reversed waves

2016 ◽  
Vol 374 (2069) ◽  
pp. 20150156 ◽  
Author(s):  
Mathias Fink
Keyword(s):  
Wave Propagation ◽  
Time Reversal ◽  
Degrees Of Freedom ◽  
Point Of View ◽  
Propagation Time ◽  
Reversal Invariance ◽  
Spatial Boundary ◽  
Dual Approaches ◽  
Spatio Temporal

Time-reversal invariance can be exploited in wave physics to control wave propagation in complex media. Because time and space play a similar role in wave propagation, time-reversed waves can be obtained by manipulating spatial boundaries or by manipulating time boundaries. The two dual approaches will be discussed in this paper. The first approach uses ‘time-reversal mirrors’ with a wave manipulation along a spatial boundary sampled by a finite number of antennas. Related to this method, the role of the spatio-temporal degrees of freedom of the wavefield will be emphasized. In a second approach, waves are manipulated from a time boundary and we show that ‘instantaneous time mirrors’, mimicking the Loschmidt point of view, simultaneously acting in the entire space at once can also radiate time-reversed waves.

Configuration Robustness Analysis of the Optimal Design of Cable-Driven Manipulators

2016 ◽  
Vol 8 (6) ◽  
Author(s):  
Joshua T. Bryson ◽  
Xin Jin ◽  
Sunil K. Agrawal
Keyword(s):  
Optimal Design ◽  
Stochastic Optimization ◽  
High Dimension ◽  
Degrees Of Freedom ◽  
Robustness Analysis ◽  
Optimal Solution ◽  
Design Parameters ◽  
Robot Leg ◽  
Robot Performance

Designing an effective cable architecture for a cable-driven robot becomes challenging as the number of cables and degrees of freedom of the robot increase. A methodology has been previously developed to identify the optimal design of a cable-driven robot for a given task using stochastic optimization. This approach is effective in providing an optimal solution for robots with high-dimension design spaces, but does not provide insights into the robustness of the optimal solution to errors in the configuration parameters that arise in the implementation of a design. In this work, a methodology is developed to analyze the robustness of the performance of an optimal design to changes in the configuration parameters. This robustness analysis can be used to inform the implementation of the optimal design into a robot while taking into account the precision and tolerances of the implementation. An optimized cable-driven robot leg is used as a motivating example to illustrate the application of the configuration robustness analysis. Following the methodology, the effect on robot performance due to design variations is analyzed, and a modified design is developed which minimizes the potential performance degradations due to implementation errors in the design parameters. A robot leg is constructed and is used to validate the robustness analysis by demonstrating the predicted effects of variations in the design parameters on the performance of the robot.

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

The enteric nervous system of echinoderms: unexpected complexity revealed by neurochemical analysis

2001 ◽  
Vol 204 (5) ◽  
pp. 865-873
Author(s):  
J.E. Garcia-Arraras ◽  
M. Rojas-Soto ◽  
L.B. Jimenez ◽  
L. Diaz-Miranda
Keyword(s):  
Nervous System ◽  
Enteric Nervous System ◽  
Digestive Tract ◽  
Radial Nerve ◽  
Digestive System ◽  
Nerve Ring ◽  
Point Of View ◽  
Distinct Component ◽  
Future Studies ◽  
Neurochemical Analysis

Echinoderms are one of the most important groups of metazoans from the point of view of evolution, ecology and abundance. Nevertheless, their nervous system has been little studied. Particularly unexplored have been the components of the nervous system that lie outside the ectoneural and hyponeural divisions of the main nerve ring and radial nerve cords. We have gathered information on the nervous components of the digestive tract of echinoderms and demonstrate an unexpected level of complexity in terms of neurons, nerve plexi, their location and neurochemistry. The nervous elements within the digestive system consist of a distinct component of the echinoderm nervous system, termed the enteric nervous system. However, the association between the enteric nervous system and the ectoneural and hyponeural components of the nervous system is not well established. Our findings also emphasize the importance of the large lacunae in the neurobiology of echinoderms, a feature that should be addressed in future studies.

THE FAMILY HISTORY OF SPINA BIFIDA CYSTICA

PEDIATRICS ◽  
1965 ◽  
Vol 35 (4) ◽  
pp. 589-595
Author(s):  
John Lorber
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Spina Bifida ◽  
Index Case ◽  
Progressive Increase ◽  
Point Of View ◽  
The Family ◽  
History Of ◽  
The Central Nervous System ◽  
Spina Bifida Cystica

1. The family histories of 722 infants who were born with spina bifida cystica were studied. 2. The index cases were referred for surgical treatment and were not selected in any way from the genetic point of view. 3. Intensive inquiries were made to obtain a complete family pedigree, including a prospective follow-up of siblings born after the index case. 4. Of 1,256 siblings 85 or 6.8% had gross malformation of the central nervous system: spina bifida cystica in 54, anencephaly in 22, and uncomplicated hydrocephalus in 9. 5. Of 306 children born after the index case 25 (8%) or 1 in 12 were affected. 6. There was a progressive increase in multiple cases in the family with increasing family size. In sibships of five or more, multiple cases occurred in 24.1%. 7. In 118 families cases of gross malformation of the central nervous system were known to have occurred among members of the family other than siblings. Cases occurred in three generations. 8. It is possible that spina bifida cystica might be a recessively inherited condition.

The phenomenon of migration of nociogenic structures in the human sensor-algic system (results of clinical and neurophysiological studies and morphological experiments)

2020 ◽  
pp. 16-24
Author(s):  
Maksim Vladimirovich Shpagin ◽  
Mikhail Valerievich Kolesnikov ◽  
Olga Yurievna Khutorskaya ◽  
Dmitriy Evgenievich Timoshkin ◽  
Artem Andreevich Belikin ◽  
...  
Keyword(s):  
Chronic Pain ◽  
Nervous System ◽  
Pain Syndrome ◽  
Point Of View ◽  
Chronic Pain Syndrome ◽  
Integrative Therapy ◽  
Neurophysiological Studies ◽  
Positive Results ◽  
Structural Point ◽  
Chronicity Of Pain

From the informational and structural point of view, the chronicity of pain is associated with the migration of nociogenic zones. The phenomenon of migration is based on the mechanisms of neuroplasticity, compensatory-restorative processes in the nervous system. On the basis of the phenomenon of migration of the nociogenic zone, a system of regional integrative therapy of chronic pain syndrome has been developed. Recommendations on the advisability of invasive shutdown of the nociogenic zone using invasive pharmacotherapy or surgical denervation have been proposed. In the course of studying the characteristics of chronic pain, depending on the duration of the disease, a direct proportional correlation was revealed between the increase in the components of pain and the duration of the pain syndrome, which can be explained by the increase in the number of nociogenic structures that form the complexity and stability of the pain syndrome. Thus, the necessity of neurodestructive interventions increases for attaining positive results. An important area of therapy is the inclusion of psychotherapy, pharmacotherapy and neuromodulation into the system of regional-integrative influence.

DARK GEOMETRY

2004 ◽  
Vol 13 (10) ◽  
pp. 2275-2279 ◽  
Author(s):  
J. A. R. CEMBRANOS ◽  
A. DOBADO ◽  
A. L. MAROTO
Keyword(s):  
Dark Matter ◽  
Extra Dimensions ◽  
Degrees Of Freedom ◽  
Planck Scale ◽  
Point Of View ◽  
Missing Mass ◽  
Brane Worlds ◽  
Mass Problem ◽  
Extra Space ◽  
The Universe

Extra-dimensional theories contain additional degrees of freedom related to the geometry of the extra space which can be interpreted as new particles. Such theories allow to reformulate most of the fundamental problems of physics from a completely different point of view. In this essay, we concentrate on the brane fluctuations which are present in brane-worlds, and how such oscillations of the own space–time geometry along curved extra dimensions can help to resolve the Universe missing mass problem. The energy scales involved in these models are low compared to the Planck scale, and this means that some of the brane fluctuations distinctive signals could be detected in future colliders and in direct or indirect dark matter searches.

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