scholarly journals The duration of reaching movement is longer than predicted by minimum variance

2016 ◽  
Vol 116 (5) ◽  
pp. 2342-2345 ◽  
Author(s):  
Chunji Wang ◽  
Yupeng Xiao ◽  
Etienne Burdet ◽  
James Gordon ◽  
Nicolas Schweighofer
Keyword(s):  
Minimum Variance ◽  
Reaching Movements ◽  
Movement Duration ◽  
Slow Movement ◽  
Reaching Movement ◽  
End Point ◽  
Parsimonious Explanation ◽  
Arm Reaching ◽  
The Central Nervous System ◽  
Duration Condition

Whether the central nervous system minimizes variability or effort in planning arm movements can be tested by measuring the preferred movement duration and end-point variability. Here we conducted an experiment in which subjects performed arm reaching movements without visual feedback in fast-, medium-, slow-, and preferred-duration conditions. Results show that 1) total end-point variance was smallest in the medium-duration condition and 2) subjects preferred to carry out movements that were slower than this medium-duration condition. A parsimonious explanation for the overall pattern of end-point errors across fast, medium, preferred, and slow movement durations is that movements are planned to minimize effort as well as end-point error due to both signal-dependent and constant noise.

Role of Non-Lesioned Hemisphere in Affected Arm Reaching Movements After Severe Stroke: A Pilot Study

2014 ◽  
Vol 95 (10) ◽  
pp. e26
Author(s):  
Sambit Mohapatra ◽  
Evan Chan ◽  
Rachael Harrington ◽  
Alexander Dromerick ◽  
Peter Turkeltaub ◽  
...  
Keyword(s):  
Pilot Study ◽  
Reaching Movements ◽  
Severe Stroke ◽  
Arm Reaching

Feedback Control of Functional Electrical Stimulation for 2-D Arm Reaching Movements

2018 ◽  
Vol 26 (10) ◽  
pp. 2033-2043 ◽  
Author(s):  
Reza Sharif Razavian ◽  
Borna Ghannadi ◽  
Naser Mehrabi ◽  
Mark Charlet ◽  
John McPhee
Keyword(s):  
Electrical Stimulation ◽  
Feedback Control ◽  
Functional Electrical Stimulation ◽  
Reaching Movements ◽  
Arm Reaching

Contrasting Neuronal Activity in the Dorsal and Ventral Premotor Areas During Preparation to Reach

2002 ◽  
Vol 87 (2) ◽  
pp. 1123-1128 ◽  
Author(s):  
Eiji Hoshi ◽  
Jun Tanji
Keyword(s):  
Neuronal Activity ◽  
Target Location ◽  
Delay Period ◽  
Reaching Movements ◽  
Target Acquisition ◽  
Trigger Signal ◽  
Arm Reaching ◽  
Motor Set ◽  
Premotor Areas

We compared neuronal activity in the dorsal and ventral premotor areas (PMd and PMv, respectively) when monkeys were preparing to perform arm-reaching movements in a motor-set period before their actual execution. They were required to select one of four possible movements (reaching to a target on the left or right, using either the left or right arm) in accordance with two sets of instruction cues, followed by a delay period, and a subsequent motor-set period. During the motor-set period, the monkeys were required to get ready for a movement-trigger signal to start the arm-reach promptly. We analyzed the activity of 211 PMd and 109 PMv neurons that showed selectivity for the combination of the two instruction cues during the motor-set period. A majority (53%) of PMd neurons exhibited activity significantly tuned to both target location and arm use, and an approximately equal number of PMd neurons showed selectivity to either forthcoming arm use or target location. In contrast, 60% of PMv neurons showed selectivity for target location only and not for arm use. These findings point to preference in the use of neuronal activity in the two areas: preparation for action in the PMd and preparation for target acquisition in the PMv.

Different Predictions by the Minimum Variance and Minimum Torque-Change Models on the Skewness of Movement Velocity Profiles

2004 ◽  
Vol 16 (10) ◽  
pp. 2021-2040 ◽  
Author(s):  
Hirokazu Tanaka ◽  
Meihua Tai ◽  
Ning Qian
Keyword(s):  
Velocity Profile ◽  
Velocity Profiles ◽  
Minimum Variance ◽  
Movement Planning ◽  
System Stability ◽  
Movement Duration ◽  
Movement Velocity ◽  
Change Models ◽  
External Forces ◽  
Minimum Torque

We investigated the differences between two well-known optimization principles for understanding movement planning: the minimum variance (MV) model of Harris and Wolpert (1998) and the minimum torque change (MTC) model of Uno, Kawato, and Suzuki (1989). Both models accurately describe the properties of human reaching movements in ordinary situations (e.g., nearly straight paths and bell-shaped velocity profiles). However, we found that the two models can make very different predictions when external forces are applied or when the movement duration is increased. We considered a second-order linear system for the motor plant that has been used previously to simulate eye movements and single-joint arm movements and were able to derive analytical solutions based on the MV and MTC assumptions. With the linear plant, the MTC model predicts that the movement velocity profile should always be symmetrical, independent of the external forces and movement duration. In contrast, the MV model strongly depends on the movement duration and the system's degree of stability; the latter in turn depends on the total forces. The MV model thus predicts a skewed velocity profile under many circumstances. For example, it predicts that the peak location should be skewed toward the end of the movement when the movement duration is increased in the absence of any elastic force. It also predicts that with appropriate viscous and elastic forces applied to increase system stability, the velocity profile should be skewed toward the beginning of the movement. The velocity profiles predicted by the MV model can even show oscillations when the plant becomes highly oscillatory. Our analytical and simulation results suggest specific experiments for testing the validity of the two models.

Optimal trajectory formation of constrained human arm reaching movements

2004 ◽  
Vol 91 (1) ◽  
Author(s):  
Ken Ohta ◽  
Mikhail M. Svinin ◽  
ZhiWei Luo ◽  
Shigeyuki Hosoe ◽  
Rafael Laboissi�re
Keyword(s):  
Optimal Trajectory ◽  
Reaching Movements ◽  
Trajectory Formation ◽  
Arm Reaching ◽  
Human Arm

Hand-held tools with complex kinematics are efficiently incorporated into movement planning and online control

2012 ◽  
Vol 108 (7) ◽  
pp. 1954-1964 ◽  
Author(s):  
Lee A. Baugh ◽  
Erica Hoe ◽  
J. Randall Flanagan
Keyword(s):  
Online Control ◽  
Movement Planning ◽  
Control Mechanisms ◽  
Movement Initiation ◽  
Reaching Movement ◽  
Hand Motion ◽  
Reversal Condition ◽  
End Point ◽  
Point Motion ◽  
Time Required

Certain hand-held tools alter the mapping between hand motion and motion of the tool end point that must be controlled in order to perform a task. For example, when using a pool cue, the motion of the cue tip is reversed relative to the hand. Previous studies have shown that the time required to initiate a reaching movement (Fernandez-Ruiz J, Wong W, Armstrong IT, Flanagan JR. Behav Brain Res 219: 8–14, 2011), or correct an ongoing reaching movement (Gritsenko V, Kalaska JF. J Neurophysiol 104: 3084–3104, 2010), is prolonged when the mapping between hand motion and motion of a cursor controlled by the hand is reversed. Here we show that these time costs can be significantly reduced when the reversal is instantiated by a virtual hand-held tool. Participants grasped the near end of a virtual tool, consisting of a rod connecting two circles, and moved the end point to displayed targets. In the reversal condition, the rod translated through, and rotated about, a pivot point such that there was a left-right reversal between hand and end point motion. In the nonreversal control, the tool translated with the hand. As expected, when only the two circles were presented, movement initiation and correction times were much longer in the reversal condition. However, when full vision of the tool was provided, the reaction time cost was almost eliminated. These results indicate that tools with complex kinematics can be efficiently incorporated into sensorimotor control mechanisms used in movement planning and online control.

Evaluation of Power-Assist System by Computer Simulation

2016 ◽  
Vol 20 (3) ◽  
pp. 477-483 ◽  
Author(s):  
Yoshiaki Taniai ◽  
◽  
Tomohide Naniwa ◽  
Yasutake Takahashi ◽  
Masayuki Kawai
Keyword(s):  
Computer Simulation ◽  
Evaluation Framework ◽  
Metabolic Energy ◽  
Evaluation Index ◽  
Optimality Principle ◽  
Upper Arm ◽  
Reaching Movement ◽  
Effective Power ◽  
Arm Reaching ◽  
Motor Paralysis

Powered exoskeletons have been proposed and developed in various works with the aim of compensating for motor paralysis or reducing weight, workload, or metabolic energy consumption. However, development of the power-assist system depends on the development and evaluation of real powered exoskeletons, and few studies have evaluated the performance of the power-assist system by means of computer simulation. In this paper, we propose an evaluation framework based on computer simulation for the development of an effective power-assist system and demonstrate an analysis of a power-assisted upper-arm reaching movement. We employed the optimality principle to obtain the adapted movements of humans for power-assist systems and compared the performances of power- and non-power-assisted movements in terms of the evaluation index of the power-assist system.

The modulatory influence of end-point controllability on decisions between actions

2012 ◽  
Vol 108 (6) ◽  
pp. 1764-1780 ◽  
Author(s):  
Ignasi Cos ◽  
Farid Medleg ◽  
Paul Cisek
Keyword(s):  
Selection Process ◽  
Dynamic Properties ◽  
Human Subjects ◽  
Reaching Movements ◽  
End Point ◽  
Gradual Process ◽  
Path Distance ◽  
Maximal Mobility ◽  
Motor Actions ◽  
Biomechanical Factors

Recent work has shown that human subjects are able to predict the biomechanical ease of potential reaching movements and use these predictions to influence their choices. Here, we examined how reach decisions are influenced by specific biomechanical factors related to the control of end-point stability, such as aiming accuracy or stopping control. Human subjects made free choices between two potential reaching movements that varied in terms of path distance and biomechanical cost in four separate blocks that additionally varied two constraints: the width of the targets (narrow or wide) and the requirement of stopping in them. When movements were unconstrained (very wide targets and no requirement of stopping), subjects' choices were strongly biased toward directions aligned with the direction of maximal mobility. However, as the movements became progressively constrained, factors related to the control of the end point gained relevance, thus reducing this bias. This demonstrates that, before movement onset, constraints such as stopping and aiming participate in a remarkably adaptive and flexible action selection process that trades off the advantage of moving along directions of maximal mobility for unconstrained movements against exploiting biomechanical anisotropies to facilitate control of end-point stability whenever the movement constraints require it. These results support a view of decision making between motor actions as a highly context-dependent gradual process in which the subjective desirability of potential actions is influenced by their dynamic properties in relation to the intrinsic properties of the motor apparatus.

10 Modulation of arm reaching movements during hand-related verb processing in Parkinson’s patients

Basal Ganglia ◽  
2012 ◽  
Vol 2 (4) ◽  
pp. 260 ◽  
Author(s):  
S. Spadacenta ◽  
G. Giannini ◽  
N. Modugno ◽  
G. Mirabella
Keyword(s):  
Reaching Movements ◽  
Arm Reaching ◽  
Verb Processing
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