scholarly journals Author Correction: Costs of position, velocity, and force requirements in optimal control induce triphasic muscle activation during reaching movement

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Yuki Ueyama
Keyword(s):  
Optimal Control ◽  
Muscle Activation ◽  
Reaching Movement

scholarly journals Costs of position, velocity, and force requirements in optimal control induce triphasic muscle activation during reaching movement

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Yuki Ueyama
Keyword(s):  
Optimal Control ◽  
Nervous System ◽  
Muscle Activation ◽  
Arm Movement ◽  
The Body ◽  
Activation Patterns ◽  
Reaching Movement ◽  
Muscle Activation Patterns ◽  
Antagonist Muscles ◽  
Neural Input

AbstractThe nervous system activates a pair of agonist and antagonist muscles to determine the muscle activation pattern for a desired movement. Although there is a problem with redundancy, it is solved immediately, and movements are generated with characteristic muscle activation patterns in which antagonistic muscle pairs show alternate bursts with a triphasic shape. To investigate the requirements for deriving this pattern, this study simulated arm movement numerically by adopting a musculoskeletal arm model and an optimal control. The simulation reproduced the triphasic electromyogram (EMG) pattern observed in a reaching movement using a cost function that considered three terms: end-point position, velocity, and force required; the function minimised neural input. The first, second, and third bursts of muscle activity were generated by the cost terms of position, velocity, and force, respectively. Thus, we concluded that the costs of position, velocity, and force requirements in optimal control can induce triphasic EMG patterns. Therefore, we suggest that the nervous system may control the body by using an optimal control mechanism that adopts the costs of position, velocity, and force required; these costs serve to initiate, decelerate, and stabilise movement, respectively.

scholarly journals The costs of positon, velocity and force requirements in optimal control induce triphasic muscle activation during reaching movement

2021 ◽  
Author(s):  
Yuki Ueyama
Keyword(s):  
Optimal Control ◽  
Nervous System ◽  
Muscle Activation ◽  
Arm Movement ◽  
The Body ◽  
Activation Patterns ◽  
Reaching Movement ◽  
Muscle Activation Patterns ◽  
Antagonist Muscles ◽  
Neural Input

Abstract The nervous system activates a pair of agonist and antagonist muscles to determine the muscle activation pattern for a desired movement. Although there is a problem with redundancy, it is solved immediately, and movements are generated with characteristic muscle activation patterns in which antagonistic muscle pairs show alternate bursts with a triphasic shape. To investigate the requirements for deriving this pattern, this study simulated arm movement numerically by adopting a musculoskeletal arm model and an optimal control based on the minimization of neural input. The simulation reproduced the triphasic electromyogram (EMG) pattern observed in a reaching movement using a cost function that considered three terms: end-point position, velocity, and force required. The first, second and third bursts of muscle activity were generated by the cost terms of position, velocity and force, respectively. Thus we concluded that the costs of position, velocity and force requirements in optimal control can induce triphasic EMG patterns. Therefore we suggest that the nervous system may control the body by using an optimal control mechanism that adopts the costs of position, velocity and force required, which serve to initiate, decelerate and stabilize movement, respectively.

Dynamic Model of the Octopus Arm. I. Biomechanics of the Octopus Reaching Movement

2005 ◽  
Vol 94 (2) ◽  
pp. 1443-1458 ◽  
Author(s):  
Yoram Yekutieli ◽  
Roni Sagiv-Zohar ◽  
Ranit Aharonov ◽  
Yaakov Engel ◽  
Binyamin Hochner ◽  
...  
Keyword(s):  
Drag Coefficient ◽  
Dynamic Model ◽  
Muscle Activation ◽  
Movement Control ◽  
Constant Volume ◽  
Reaching Movement ◽  
Drag Forces ◽  
Direction Of Movement ◽  
Internal Forces ◽  
External Forces

The octopus arm requires special motor control schemes because it consists almost entirely of muscles and lacks a rigid skeletal support. Here we present a 2D dynamic model of the octopus arm to explore possible strategies of movement control in this muscular hydrostat. The arm is modeled as a multisegment structure, each segment containing longitudinal and transverse muscles and maintaining a constant volume, a prominent feature of muscular hydrostats. The input to the model is the degree of activation of each of its muscles. The model includes the external forces of gravity, buoyancy, and water drag forces (experimentally estimated here). It also includes the internal forces generated by the arm muscles and the forces responsible for maintaining a constant volume. Using this dynamic model to investigate the octopus reaching movement and to explore the mechanisms of bend propagation that characterize this movement, we found the following. 1) A simple command producing a wave of muscle activation moving at a constant velocity is sufficient to replicate the natural reaching movements with similar kinematic features. 2) The biomechanical mechanism that produces the reaching movement is a stiffening wave of muscle contraction that pushes a bend forward along the arm. 3) The perpendicular drag coefficient for an octopus arm is nearly 50 times larger than the tangential drag coefficient. During a reaching movement, only a small portion of the arm is oriented perpendicular to the direction of movement, thus minimizing the drag force.

Optimal control of reaching includes kinematic constraints

2013 ◽  
Vol 110 (1) ◽  
pp. 1-11 ◽  
Author(s):  
Michael Mistry ◽  
Evangelos Theodorou ◽  
Stefan Schaal ◽  
Mitsuo Kawato
Keyword(s):  
Optimal Control ◽  
Stochastic Optimal Control ◽  
Optimal Control Theory ◽  
Internal Model ◽  
Reaching Movement ◽  
Reaching Task ◽  
Hand Trajectory ◽  
Curved Trajectories ◽  
Hand Off ◽  
Directional Preference

We investigate adaptation under a reaching task with an acceleration-based force field perturbation designed to alter the nominal straight hand trajectory in a potentially benign manner: pushing the hand off course in one direction before subsequently restoring towards the target. In this particular task, an explicit strategy to reduce motor effort requires a distinct deviation from the nominal rectilinear hand trajectory. Rather, our results display a clear directional preference during learning, as subjects adapted perturbed curved trajectories towards their initial baselines. We model this behavior using the framework of stochastic optimal control theory and an objective function that trades off the discordant requirements of 1) target accuracy, 2) motor effort, and 3) kinematic invariance. Our work addresses the underlying objective of a reaching movement, and we suggest that robustness, particularly against internal model uncertainly, is as essential to the reaching task as terminal accuracy and energy efficiency.

Optimal Control and Forward Dynamics of Human Periodic Motions Using Fourier Series for Muscle Excitation Patterns

2013 ◽  
Vol 9 (2) ◽  
Author(s):  
Mohammad Sharif Shourijeh ◽  
John McPhee
Keyword(s):  
Optimal Control ◽  
Fourier Series ◽  
Dynamic Optimization ◽  
Muscle Activation ◽  
Metabolic Energy ◽  
Forward Dynamics ◽  
Objective Functions ◽  
Periodic Motions ◽  
Dynamic Simulations ◽  
Time Integral

Forward dynamic simulations of a periodic forearm motion were developed in order to explore the efficiency of using a Fourier-series-based parameterization function for muscle excitations within dynamic optimization. The specific objectives of this study were to develop such a simulation and validate the predictions. Several time-integral objective functions, including muscle activation effort and metabolic energy, were used to see the effects of each on the optimal results. For validation, the motion and muscle electromyograms (EMGs) of three adult subjects were captured, where each trial was replicated twice. Fourier-series pattern parameterization was found to be an efficient choice for the muscle excitations in simulating human musculoskeletal dynamics.

Optimal Control of Redundant Muscles in Step-Tracking Wrist Movements

2005 ◽  
Vol 94 (6) ◽  
pp. 4244-4255 ◽  
Author(s):  
Masahiko Haruno ◽  
Daniel M. Wolpert
Keyword(s):  
Optimal Control ◽  
Nervous System ◽  
Muscle Activation ◽  
Control Mechanisms ◽  
Specific Sequence ◽  
Data Set ◽  
Activation Patterns ◽  
Motor Commands ◽  
Preferred Direction ◽  
Agonist And Antagonist

An important question in motor neuroscience is how the nervous system controls the spatiotemporal activation patterns of redundant muscles in generating accurate movements. The redundant muscles may not only underlie the flexibility of our movements but also pose the challenging problem of how to select a specific sequence of muscle activation from the huge number of possible activations. Here, we propose that noise in the motor command that has an influence on task achievement should be considered in determining the optimal motor commands over redundant muscles. We propose an optimal control model for step-tracking wrist movements with redundant muscles that minimizes the end-point variance under signal-dependent noise. Step-tracking wrist movements of human and nonhuman primates provide a detailed data set to investigate the control mechanisms in movements with redundant muscles. The experimental EMG data can be summarized by two eminent features: 1) amplitude-graded EMG pattern, where the timing of the activity of the agonist and antagonist bursts show slight variations with changes in movement directions, and only the amplitude of activity is modulated; and 2) cosine tuning for movement directions exhibited by the agonist and antagonist bursts, and the discrepancy found between a muscle's agonist preferred direction and its pulling direction. In addition, it is also an important observation that subjects often overshoot the target. We demonstrate that the proposed model captures not only the spatiotemporal activation patterns of wrist muscles but also trajectory overshooting. This suggests that when recruiting redundant muscles, the nervous system may optimize the motor commands across the muscles to reduce the negative effects of motor noise.

Influence of the globus pallidus on arm movements in monkeys. III. Timing of movement-related information

1985 ◽  
Vol 54 (2) ◽  
pp. 433-448 ◽  
Author(s):  
M. E. Anderson ◽  
F. B. Horak
Keyword(s):  
Reaction Time ◽  
Globus Pallidus ◽  
Muscle Activation ◽  
Movement Time ◽  
Emg Activity ◽  
Movement Velocity ◽  
Critical Stimulus ◽  
Reaching Movement ◽  
Stimulus Period ◽  
Arm Reaching

Monkeys were trained to make a visually triggered arm-reaching movement to a lighted button in a simple reaction-time paradigm, during which the reaction time (RT) and movement time (MT) were measured. Stimulus trains of varying duration were applied at various times before and during the movement at locations in the globus pallidus where application of long stimulus trains caused increased MTs. A critical stimulus period was identified during which stimulus application effectively prolonged MTs. The activity of pallidal neurons was examined during performance of the same behavioral task. More than 60% of the neurons examined showed task-related changes in activity that began before or during the reaching movement. For 45% of these cells, the initial change in firing occurred during the critical stimulus period, 50-150 ms before mechanically detected movement. Comparison of the critical stimulus period, the time of task-related changes in the discharge of pallidal neurons, and the time of EMG activity in muscles acting at the back, shoulder, elbow, and wrist revealed that both the critical stimulus period and changes in neuronal discharge occurred at or after initial muscle activation and during the buildup of EMG activity. These data are consistent with a model in which the globus pallidus plays a role in scaling the magnitude of muscle activity that determines movement velocity without affecting the initiation or sequential organization of the programmed motor output.

scholarly journals Control of Hand Impedance Under Static Conditions and During Reaching Movement

2007 ◽  
Vol 97 (4) ◽  
pp. 2676-2685 ◽  
Author(s):  
Mohammad Darainy ◽  
Farzad Towhidkhah ◽  
David J. Ostry
Keyword(s):  
Muscle Activation ◽  
Impedance Control ◽  
Longitudinal Direction ◽  
Movement Direction ◽  
Reference Trajectory ◽  
Reaching Movement ◽  
Counterclockwise Rotation ◽  
Modeling Studies ◽  
Environmental Instability ◽  
Static Conditions

It is known that humans can modify the impedance of the musculoskeletal periphery, but the extent of this modification is uncertain. Previous studies on impedance control under static conditions indicate a limited ability to modify impedance, whereas studies of impedance control during reaching in unstable environments suggest a greater range of impedance modification. As a first step in accounting for this difference, we quantified the extent to which stiffness changes from posture to movement even when there are no destabilizing forces. Hand stiffness was estimated under static conditions and at the same position during both longitudinal (near to far) and lateral movements using a position-servo technique. A new method was developed to predict the hand “reference” trajectory for purposes of estimating stiffness. For movements in a longitudinal direction, there was considerable counterclockwise rotation of the hand stiffness ellipse relative to stiffness under static conditions. In contrast, a small counterclockwise rotation was observed during lateral movement. In the modeling studies, even when we used the same modeled cocontraction level during posture and movement, we found that there was a substantial difference in the orientation of the stiffness ellipse, comparable with that observed empirically. Indeed, the main determinant of the orientation of the ellipse in our modeling studies was the movement direction and the muscle activation associated with movement. Changes in the cocontraction level and the balance of cocontraction had smaller effects. Thus even when there is no environmental instability, the orientation of stiffness ellipse changes during movement in a manner that varies with movement direction.

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