Organizing principles for single joint movements. III. Speed-insensitive strategy as a default

1990 ◽  
Vol 63 (3) ◽  
pp. 625-636 ◽  
Author(s):  
G. L. Gottlieb ◽  
D. M. Corcos ◽  
G. C. Agarwal ◽  
M. L. Latash
Keyword(s):  
Human Subjects ◽  
Movement Control ◽  
Initial Position ◽  
Initial Slope ◽  
Range Of Movement ◽  
Stationary Target ◽  
Wide Range ◽  
Inertial Torque ◽  
Maximal Speed ◽  
Speed Accuracy

1. Human subjects made discrete elbow flexions in a horizontal plane over different distances, from a stationary initial position to a visually defined stationary target 9 degrees wide. We measured joint angle, acceleration, and electromyograms (EMGs) from two agonist and two antagonist muscles. 2. Subjects made movements over four different distances following one of four different instructions. The first instructed the subject simply to choose a comfortable speed. The other three explicitly emphasized either speed, accuracy, or maintenance of the "same" speed over different distances. These instructions produced a wide range of movement velocities. 3. The initial rises of the acceleration (and therefore of the inertial torque), as well as the initial slope of the agonist EMG, were all invariant over changes in the target distance for any single instruction but were all sensitive to the given instruction. 4. Our results demonstrate that the speed-insensitive strategy is a standard or default pattern for performing movements that may be carried out for different instructions over a wide range of speeds. A uniform intensity of excitation pulse is not a byproduct of moving at maximal speed. Submaximal intensities are associated with submaximal speeds and are a selected feature of the pattern of movement control.

Organizing principles for single-joint movements. II. A speed-sensitive strategy

1989 ◽  
Vol 62 (2) ◽  
pp. 358-368 ◽  
Author(s):  
D. M. Corcos ◽  
G. L. Gottlieb ◽  
G. C. Agarwal
Keyword(s):  
Muscle Activation ◽  
Human Subjects ◽  
Movement Time ◽  
Initial Position ◽  
Joint Torque ◽  
Movement Speed ◽  
Movement Kinematics ◽  
Antagonist Muscles ◽  
Speed Accuracy ◽  
Organizing Principles

1. Normal human subjects made discrete flexions of the elbow over a fixed distance in the horizontal plane from a stationary initial position to a visually defined target. We measured joint angle, acceleration, and electromyograms (EMGs) from two agonist and two antagonist muscles. 2. Changes in movement speed were elicited either by explicit instruction to the subject or by adjusting the target width. Instructions always required accurately stopping in the target zone. 3. Peak inertial torques and accelerations, movement times, and integrated EMGs were all highly correlated with speed. We show that inertial torque can be used as a linking variable that is almost sufficient to explain all correlations between the task, the EMG, and movement kinematics. 4. When subjects perform tasks that require control of movement speed, they adjust the rate at which torque is developed by the muscles. This rate is modulated by the way in which the muscles are activated. The rate at which joint torque develops is correlated with the rate at which the agonist EMG rises as well as with integrated EMG. 5. The antagonist EMG shows two components. The latency of the first is 30-50 ms and independent of movement dynamics. The latency of the second component is proportional to movement time. The rate of rise and area of both components scale with torque. 6. We propose organizing principles for the control of single-joint movements in which tasks are performed by one of two strategies. These are called speed-insensitive and speed-sensitive strategies. 7. A model is proposed in which movements made under a speed-sensitive strategy are executed by controlling the intensity of an excitation pulse delivered to the motoneuron pool. The effect is to regulate the rate at which joint torque, and consequently acceleration, increases. 8. Movements of variable distance, speed, accuracy, and load are shown to be controlled by one of two consistent sets of rules for muscle activation. These rules apply to the control of both the agonist and antagonist muscles. Rules of activation lead to distinguishable patterns of EMG and torque development. All observable changes in movement kinematics are explained as deterministic consequences of these effects.

Organizing principles for single-joint movements. I. A speed-insensitive strategy

1989 ◽  
Vol 62 (2) ◽  
pp. 342-357 ◽  
Author(s):  
G. L. Gottlieb ◽  
D. M. Corcos ◽  
G. C. Agarwal
Keyword(s):  
Human Subjects ◽  
Movement Time ◽  
Muscle Length ◽  
Initial Position ◽  
Inertial Load ◽  
Antagonist Muscles ◽  
Human Movements ◽  
Inertial Torque ◽  
Highly Correlated ◽  
Organizing Principles

1. Normal human subjects made discrete elbow flexions and extensions in the horizontal plane from a stationary initial position to visually defined targets at different distances with a constant inertial load or made flexions to a visually defined target with different inertial loads. We measured joint angle, acceleration, and electromyograms (EMGs) from two agonist and two antagonist muscles. 2. Subjects were instructed to move their limbs accurately but quickly to the targets. Movements of greater distances or lesser loads were performed at higher velocities. 3. Peak inertial torque, acceleration and velocity, movement time, and integrated, rectified EMG were all highly correlated with the task variables, distance and inertial load. We show that peak inertial torque can be used as a linking variable that is almost sufficient to explain all correlations between the tasks, the EMG, and movement kinematics. 4. The rate at which subjects initially developed torque to accelerate their movements was invariant over changes in the value of either task variable. The rising phase of the agonist EMG was also independent of the distance or load moved. 5. Two components were distinguished in the antagonist EMG. The first had a relatively constant latency and amplitude. It terminated on the onset of the second and larger component at a latency that was delayed as both distance and load increased. 6. The integrated, rectified antagonist EMG was proportional to inertial load and peak decelerating torque for changes in inertial load. When target distance varied, proportionality between peak decelerating torque and antagonist EMG could be found if correction was made for the effects of muscle length on the torque-EMG relationship. 7. We propose organizing principles for the control of single-joint human movements in which tasks are performed by one of two strategies. These are called speed-insensitive and speed-sensitive strategies. 8. A model is described in which movements made under a speed-insensitive strategy are executed by controlling the duration and the relative timing of amplitude invariant patterns of activation to the spinal motoneuron pools.

A Cortico-Spinal Model of Reaching and Proprioception under Multiple Task Constraints

1998 ◽  
Vol 10 (4) ◽  
pp. 425-444 ◽  
Author(s):  
Paul Cisek ◽  
Stephen Grossberg ◽  
Daniel Bullock
Keyword(s):  
Movement Control ◽  
Arm Movement ◽  
Movement Speed ◽  
Dynamic Feedback ◽  
Range Of Movement ◽  
Tonic Vibration Reflex ◽  
Task Constraints ◽  
Feedback Information ◽  
Wide Range ◽  
The Brain

A model of cortico-spinal trajectory generation for voluntary reaching movements is developed to functionally interpret a broad range of behavioral, physiological, and anatomical data. The model simulates how arm movements achieve their remarkable efficiency and accuracy in response to widely varying positional, speed, and force constraints. A key issue in arm movement control is how the brain copes with such a wide range of movement contexts. The model suggests how the brain may set automatic and volitional gating mechanisms to vary the balance of static and dynamic feedback information to guide the movement command and to compensate for external forces. For example, with increasing movement speed, the system shifts from a feedback position controller to a feedforward trajectory generator with superimposed dynamics compensation. Simulations of the model illustrate how it reproduces the effects of elastic loads on fast movements, endpoint errors in Coriolis fields, and several effects of muscle tendon vibration, including tonic and antagonist vibration reflexes, position and movement illusions, effects of obstructing the tonic vibration reflex, and reaching undershoots caused by antagonist vibration.

The Costs of Non-Simultaneity of Action

1982 ◽  
Vol 26 (9) ◽  
pp. 808-808
Author(s):  
D. Goodman ◽  
J. A. S. Kelso ◽  
D. L. Southard
Keyword(s):  
Reaction Times ◽  
Movement Control ◽  
Task Demands ◽  
Simultaneous Action ◽  
System Control ◽  
Timing Constraints ◽  
Movement Initiation ◽  
Wide Range ◽  
Speed Accuracy ◽  
Accuracy Relationship

Raibert (1978) has pointed out that our limbs are useful tools only if they will do our bidding. While it is abundantly clear that, for the most part, our limbs do indeed do as bidded, what is not clear is how the language of our wishes is translated into a language which motoneurons and muscles understand. A simple example should suffice: “close your eyes and move your hand to grasp the dial and then twist counterclockwise”. Even though this specification gives no explicit information about the requisite muscle forces, the action is carried out as intended. This, in spite of the fact that answers to the question only recently phrased by Stein (1982, in press) as “What muscle variable(s) does the nervous system control in limb movements?” still eludes us. The behavioural approach adopted in the present set of experiments aims to shed some light on the above issue by examining timing constraints. A pervasive finding in movement control and coordination is that the relative or proportional timing of an act remains invariant over a wide range of kinematic changes in the act (e.g. amplitude and force). In previous work (Kelso, Southard and Goodman, 1979) it was shown that even under differing task demands in a two-handed coordination task, the two hands exhibit simultaneity of response. In the present study movement initiation and execution are examined when the timing demands of the task are altered for each hand. Reaction times in the first two experiments were inflated relative to control conditions which required simultaneity of movement. This was taken as preliminary indication of the costs involved in preparing for non-simultaneous action. The third experiment further examined the issue in a choice reaction time paradigm. Either simultaneous or non-simultaneous two handed movements were required. Twelve subjects performed 4 blocks of 48 trials in which they responded to one of two equi-probable stimuli by performing a two-hand response. The costs of non-simultaneity of action are revealed by examining the characteristics of the speed-accuracy relationship. Reaction times were inflated on those trials requiring a non-simultaneous response. However, movement times for the hand striking first (in the non-simultaneous trials) were not significantly different from the movement times of those trials in which a simultaneous response was required. Evidence is provided that timing is intrinsic to the organization (as distinct from the execution) of an act. This regulation of timing and costs incurred by disruption are further discussed from a dynamics perspective.

Krypton 85 myocardial blood flow: precordial scintillation versus coronary sinus sampling

1965 ◽  
Vol 209 (4) ◽  
pp. 705-710 ◽  
Author(s):  
Michael D. Klein ◽  
Lawrence S. Cohen ◽  
Richard Gorlin
Keyword(s):  
Blood Flow ◽  
Myocardial Blood Flow ◽  
Coronary Sinus ◽  
Human Subjects ◽  
Radioactive Decay ◽  
Empirical Correction ◽  
Wide Range ◽  
Actual Flow ◽  
Flow Through ◽  
High Degree

Myocardial blood flow in human subjects was assessed by comparative simultaneous measurement of krypton 85 radioactive decay from coronary sinus and precordial scintillation. Empirical correction of postclearance background from precordial curves yielded a high degree of correlation between flows derived from the two sampling sites (r = .889, P < .001). Comparison of left and right coronary flows in nine subjects revealed similarity in flow through the two vessels over a wide range of actual flow values (r = .945, P < .001).

Trading accuracy for speed over the course of a decision

2021 ◽  
Author(s):  
Gerard Derosiere ◽  
David Thura ◽  
Paul Cisek ◽  
Julie Duqué
Keyword(s):  
Late Stage ◽  
Human Subjects ◽  
Sensory Information ◽  
Decision Task ◽  
Unique Extension ◽  
Dynamic Changes ◽  
Performance Accuracy ◽  
Accuracy Criterion ◽  
Speed Accuracy ◽  
Accuracy Tradeoff

Humans and other animals often need to balance the desire to gather sensory information (to make the best choice) with the urgency to act, facing a speed-accuracy tradeoff (SAT). Given the ubiquity of SAT across species, extensive research has been devoted to understanding the computational mechanisms allowing its regulation at different timescales, including from one context to another, and from one decision to another. However, animals must frequently change their SAT on even shorter timescales - i.e., over the course of an ongoing decision - and little is known about the mechanisms that allow such rapid adaptations. The present study aimed at addressing this issue. Human subjects performed a decision task with changing evidence. In this task, subjects received rewards for correct answers but incurred penalties for mistakes. An increase or a decrease in penalty occurring halfway through the trial promoted rapid SAT shifts, favoring speeded decisions either in the early or in the late stage of the trial. Importantly, these shifts were associated with stage-specific adjustments in the accuracy criterion exploited for committing to a choice. Those subjects who decreased the most their accuracy criterion at a given decision stage exhibited the highest gain in speed, but also the highest cost in terms of performance accuracy at that time. Altogether, the current findings offer a unique extension of previous work, by suggesting that dynamic changes in accuracy criterion allow the regulation of the SAT within the timescale of a single decision.

An Efficient Smartphone Assisted Indoor Localization with Tracking Approach using Glowworm Swarm Optimization Algorithm

2021 ◽  
pp. 101-107
Author(s):  
Mohammad Alshehri ◽  
Keyword(s):  
Real Time ◽  
Indoor Localization ◽  
Initial Position ◽  
Swarm Optimization ◽  
The Real ◽  
Assisted Navigation ◽  
Glowworm Swarm Optimization ◽  
Tracking Process ◽  
Wide Range ◽  
Localization And Tracking

Presently, a precise localization and tracking process becomes significant to enable smartphone-assisted navigation to maximize accuracy in the real-time environment. Fingerprint-based localization is the commonly available model for accomplishing effective outcomes. With this motivation, this study focuses on designing efficient smartphone-assisted indoor localization and tracking models using the glowworm swarm optimization (ILT-GSO) algorithm. The ILT-GSO algorithm involves creating a GSO algorithm based on the light-emissive characteristics of glowworms to determine the location. In addition, the Kalman filter is applied to mitigate the estimation process and update the initial position of the glowworms. A wide range of experiments was carried out, and the results are investigated in terms of distinct evaluation metrics. The simulation outcome demonstrated considerable enhancement in the real-time environment and reduced the computational complexity. The ILT-GSO algorithm has resulted in an increased localization performance with minimal error over the recent techniques.

Predictive human pursuit and "orbital goal" of microstimulated smooth eye movements

1995 ◽  
Vol 74 (3) ◽  
pp. 1358-1361 ◽  
Author(s):  
P. van Gelder ◽  
S. Lebedev ◽  
W. H. Tsui
Keyword(s):  
Smooth Pursuit ◽  
Human Subjects ◽  
Initial Position ◽  
Common Point ◽  
Frontal Eye Field ◽  
Moving Target ◽  
The Gaze ◽  
Target Trajectory ◽  
Eye Field ◽  
Normal Human

1. Anticipatory saccades in smooth pursuit move the point of gaze from near the moving target to well ahead of it, interrupting accurate smooth pursuit. Their effects on the pursuit process were studied in 22 normal human subjects. We presented horizontal periodic target trajectories of 30 degrees amplitude and 30 degrees/s constant velocity or 0.4 Hz sinusoidal velocity in 40-s trials. Saccades and surrounding smooth eye movement (SEM) segments were marked and classified by computer. 2. Anticipatory saccades were often followed by slowed SEM that tended to intercept the target at the endpoint of its trajectory. This was seen in the distribution of projections of the initial 60 ms of postsaccadic SEM to the time of the trajectory endpoint. Magnitude of this SEM tended to follow a function of the time and location of the endpoint of the anticipatory saccade, decreasing as the anticipatory saccades landed closer to the trajectory endpoint. 3. The time and location of the target trajectory endpoint seemed to be the goal for this SEM. We believe this to demonstrate the predictive use of the period and amplitude of the trajectory in smooth pursuit, apart from the instantaneous velocity match of the target. 4. Gottlieb and coworkers in the frontal eye field and Ron and Robinson in the cerebellum produced SEMs in the monkey by microstimulation. At some sites in both structures, direction and velocity of the SEMs depended on the initial position of the eye in that the elicited SEMs appeared to be converging toward a common point, or "orbital goal", and the SEM velocity diminished as the gaze neared that goal.2+ Both our SEM after anticipatory saccades and microstimulated SEM in the monkey slowed as the initial position was brought closer to the inferred orbital goal. This similarity suggests that the goal-directed SEM sites in the monkey might be part of a mechanism for predictive pursuit.

scholarly journals A Robust Tracking-by-Detection Algorithm Using Adaptive Accumulated Frame Differencing and Corner Features

2020 ◽  
Vol 6 (4) ◽  
pp. 25
Author(s):  
Nahlah Algethami ◽  
Sam Redfern
Keyword(s):  
Detection Algorithm ◽  
Image Features ◽  
Corner Detection ◽  
Wide Angle ◽  
Tracking Accuracy ◽  
Range Of Movement ◽  
Illumination Variation ◽  
Detection Techniques ◽  
Wide Range ◽  
Tracking By Detection

We propose a tracking-by-detection algorithm to track the movements of meeting participants from an overhead camera. An advantage of using overhead cameras is that all objects can typically be seen clearly, with little occlusion; however, detecting people from a wide-angle overhead view also poses challenges such as people’s appearance significantly changing due to their position in the wide-angle image, and generally from a lack of strong image features. Our experimental datasets do not include empty meeting rooms, and this means that standard motion based detection techniques (e.g., background subtraction or consecutive frame differencing) struggle since there is no prior knowledge for a background model. Additionally, standard techniques may perform poorly when there is a wide range of movement behaviours (e.g. periods of no movement and periods of fast movement), as is often the case in meetings. Our algorithm uses a novel coarse-to-fine detection and tracking approach, combining motion detection using adaptive accumulated frame differencing (AAFD) with Shi-Tomasi corner detection. We present quantitative and qualitative evaluation which demonstrates the robustness of our method to track people in environments where object features are not clear and have similar colour to the background. We show that our approach achieves excellent performance in terms of the multiple object tracking accuracy (MOTA) metrics, and that it is particularly robust to initialisation differences when compared with baseline and state of the art trackers. Using the Online Tracking Benchmark (OTB) videos we also demonstrate that our tracker is very strong in the presence of background clutter, deformation and illumination variation.

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