scholarly journals Generalizing movement patterns following shoulder fixation

2019 ◽  
Author(s):  
Rodrigo S. Maeda ◽  
Julia M. Zdybal ◽  
Paul L. Gribble ◽  
J. Andrew Pruszynski
Keyword(s):  
Feedback Control ◽  
Shoulder Joint ◽  
Substantial Reduction ◽  
Physical Property ◽  
Movement Patterns ◽  
Forearm Rotation ◽  
Reaching Task ◽  
General Internal ◽  
Shoulder Muscles ◽  
Interaction Torques

AbstractA common goal of motor learning is generalizing newly learned movement patterns beyond the training context. Here we tested whether learning a new physical property of the arm during self-initiated reaching generalizes to new arm configurations. One hundred human participants performed a single-joint elbow reaching task and/or countered mechanical perturbations that created pure elbow motion. Participants did so with the shoulder joint either free to rotate or locked by the robotic manipulandum. With the shoulder free, we found activation of shoulder extensor muscles for pure elbow extension trials, as required to counter the interaction torques that arise at the shoulder due to forearm rotation. After locking the shoulder joint, we found a substantial reduction in shoulder muscle activity that developed slowly over many trials. This reduction is appropriate because locking the shoulder joint cancels the interaction torques that arise at the shoulder to do forearm rotation and thus removes the need to activate shoulder muscles. In our first three experiments, we tested whether this reduction generalizes when reaching is self-initiated in (1) a different initial shoulder orientation, (2) a different initial elbow orientation and (3) for a different reach distance/speed. We found reliable generalization across initial shoulder orientation and reach distance/speed but not for initial elbow orientation. In our fourth experiment, we tested whether generalization is also transferred to feedback control by applying mechanical perturbations and observing reflex responses in a distinct shoulder orientation. We found robust transfer to feedback control.New & NoteworthyHere we show that learning to reduce shoulder muscles activity following shoulder fixation generalizes to other movement conditions but does not generalize globally, indicating that the nervous system does not implement such learning by modifying a general internal model of arm dynamics.DisclosuresThe authors declare no conflict of interest.

scholarly journals Generalizing movement patterns following shoulder fixation

2020 ◽  
Vol 123 (3) ◽  
pp. 1193-1205 ◽  
Author(s):  
Rodrigo S. Maeda ◽  
Julia M. Zdybal ◽  
Paul L. Gribble ◽  
J. Andrew Pruszynski
Keyword(s):  
Muscle Activity ◽  
Shoulder Joint ◽  
Internal Model ◽  
Movement Patterns ◽  
Partial Reduction ◽  
Forearm Rotation ◽  
General Internal ◽  
Shoulder Muscle ◽  
Intersegmental Dynamics ◽  
Partial Learning

Generalizing newly learned movement patterns beyond the training context is challenging for most motor learning situations. Here we tested whether learning of a new physical property of the arm during self-initiated reaching generalizes to new arm configurations. Human participants performed a single-joint elbow reaching task and/or countered mechanical perturbations that created pure elbow motion with the shoulder joint free to rotate or locked by the manipulandum. With the shoulder free, we found activation of shoulder extensor muscles for pure elbow extension trials, appropriate for countering torques that arise at the shoulder due to forearm rotation. After locking the shoulder joint, we found a partial reduction in shoulder muscle activity, appropriate because locking the shoulder joint cancels the torques that arise at the shoulder due to forearm rotation. In our first three experiments, we tested whether and to what extent this partial reduction in shoulder muscle activity generalizes when reaching in different situations: 1) different initial shoulder orientation, 2) different initial elbow orientation, and 3) different reach distance/speed. We found generalization for the different shoulder orientation and reach distance/speed as measured by a reliable reduction in shoulder activity in these situations but no generalization for the different elbow orientation. In our fourth experiment, we found that generalization is also transferred to feedback control by applying mechanical perturbations and observing reflex responses in a distinct shoulder orientation. These results indicate that partial learning of new intersegmental dynamics is not sufficient for modifying a general internal model of arm dynamics. NEW & NOTEWORTHY Here we show that partially learning to reduce shoulder muscle activity following shoulder fixation generalizes to other movement conditions, but it does not generalize globally. These findings suggest that the partial learning of new intersegmental dynamics is not sufficient for modifying a general internal model of the arm’s dynamics.

scholarly journals Feedforward and feedback control share an internal model of the arm’s dynamics

2018 ◽  
Author(s):  
Rodrigo S. Maeda ◽  
Tyler Cluff ◽  
Paul L. Gribble ◽  
J. Andrew Pruszynski
Keyword(s):  
Nervous System ◽  
Feedback Control ◽  
Shoulder Joint ◽  
Internal Model ◽  
Feedforward Control ◽  
Substantial Reduction ◽  
Baseline Phase ◽  
Intersegmental Dynamics ◽  
Adaptation Phase ◽  
Feedback Responses

AbstractHumans have a remarkable capacity to learn novel movement patterns in a wide variety of contexts. Recent work has shown that, when countering external forces, the nervous system adjusts not only voluntary (ie. feedforward) control but also reflex (ie. feedback) responses. Here we show that directly altering the physical properties of the arm (i.e. intersegmental dynamics) causes the nervous system to adjust feedforward control and that this learning also transfers to feedback responses even though they were never directly trained. In our first experiment, we altered intersegmental dynamics by asking participants to generate pure elbow movements with the shoulder joint either free to rotate or locked. Locking the shoulder joint cancels the interaction forces that arise at the shoulder during forearm rotation and thus removes the need to activate shoulder muscles to prevent shoulder joint rotation. We first asked whether the nervous system learns this altered mapping of intersegmental dynamics. In the baseline phase, we found robust activation of shoulder flexor muscles for pure elbow flexion trials prior to movement onset – as required to counter the intersegmental dynamics. After locking the shoulder joint in the adaptation phase, we found a substantial reduction in shoulder muscle activity over many trials. After unlocking the shoulder joint in the post-adaptation phase, we observed after-effects, as participants made systematic hand path errors. In our second experiment, we investigated whether such learning transfers to feedback control. Mechanical perturbations applied to the limb in the baseline phase revealed that feedback responses, like feedforward control, also appropriately countered intersegmental dynamics. In the adaptation phase, we found a substantial reduction in shoulder feedback responses – as appropriate for the altered intersegmental dynamics. We also found that this decay in shoulder feedback responses correlated across subjects with the amount of decay during feedforward control. Our work adds to the growing evidence that feedforward and feedback control share an internal model of the arm’s dynamics.

scholarly journals Compensation for Interaction Torques During Single- and Multijoint Limb Movement

1999 ◽  
Vol 82 (5) ◽  
pp. 2310-2326 ◽  
Author(s):  
Paul L. Gribble ◽  
David J. Ostry
Keyword(s):  
Human Subjects ◽  
Emg Activity ◽  
Interaction Torque ◽  
Control Signals ◽  
Shoulder Muscles ◽  
Multijoint Movements ◽  
Movement Parameters ◽  
Shoulder Kinematics ◽  
Interaction Torques ◽  
Elbow Motion

During multijoint limb movements such as reaching, rotational forces arise at one joint due to the motions of limb segments about other joints. We report the results of three experiments in which we assessed the extent to which control signals to muscles are adjusted to counteract these “interaction torques.” Human subjects performed single- and multijoint pointing movements involving shoulder and elbow motion, and movement parameters related to the magnitude and direction of interaction torques were manipulated systematically. We examined electromyographic (EMG) activity of shoulder and elbow muscles and, specifically, the relationship between EMG activity and joint interaction torque. A first set of experiments examined single-joint movements. During both single-joint elbow ( experiment 1) and shoulder ( experiment 2) movements, phasic EMG activity was observed in muscles spanning the stationary joint (shoulder muscles in experiment 1 and elbow muscles in experiment 2). This muscle activity preceded movement and varied in amplitude with the magnitude of upcoming interaction torque (the load resulting from motion of the nonstationary limb segment). In a third experiment, subjects performed multijoint movements involving simultaneous motion at the shoulder and elbow. Movement amplitude and velocity at one joint were held constant, while the direction of movement about the other joint was varied. When the direction of elbow motion was varied (flexion vs. extension) and shoulder kinematics were held constant, EMG activity in shoulder muscles varied depending on the direction of elbow motion (and hence the sign of the interaction torque arising at the shoulder). Similarly, EMG activity in elbow muscles varied depending on the direction of shoulder motion for movements in which elbow kinematics were held constant. The results from all three experiments support the idea that central control signals to muscles are adjusted, in a predictive manner, to compensate for interaction torques—loads arising at one joint that depend on motion about other joints.

scholarly journals Effects of Acupuncture on Explosive Force Production by the Healthy Female Shoulder Joint

2020 ◽  
Vol 2020 ◽  
pp. 1-7
Author(s):  
I-Lin Wang ◽  
Yi-Ming Chen ◽  
Jun Wang ◽  
Rui Hu ◽  
Ke-Ke Zhang ◽  
...  
Keyword(s):  
Shoulder Joint ◽  
Force Production ◽  
Maximum Speed ◽  
Maximum Torque ◽  
Shoulder Muscles ◽  
Potentiation Effect ◽  
Average Maximum ◽  
Significant Difference ◽  
Before And After ◽  
Explosive Force

Background. Acupuncture is often used to treat chronic conditions, such as pain. In recent years, given the importance of the explosive forces generated by shoulder muscles for the completion of motor tasks, studies in which nerves were stimulated through acupuncture to increase the explosive forces were conducted. This study explored the effect of acupuncture on explosive force production by the muscles of the female shoulder joint. Methods. Eighteen healthy women underwent shoulder adduction (Add), abduction (Abd), flexion (Flex), and extension (Ext) tests with an isokinetic measurement system. Acupuncture was used to stimulate the Zhongfu (LU1), Tianfu (LI3), Xiabai (LU4), Binao (LI14), Naohui (SJ13), Jianliao (SJ14), and Xiaoluo (SJ12) points, and electromyography (EMG) signals were recorded before and after acupuncture. Results. After acupuncture, there was a significant difference in the average maximum work, the average maximum power, the average maximum speed, the total work in Add/Abd and Flex/Ext, the EMG signals, and the stiffness of the muscles in Abd and Ext ( P < 0.05 ). There were no significant differences in the average maximum torque in Abd or Flex. Conclusion. Based on the results, there may be a significant correlation between the manipulation of different acupoints by acupuncture and the average maximum torque and stiffness. Acupuncture may stimulate nerves to activate muscles and induce a postactivation potentiation effect that improves explosive force production. Therefore, acupuncture as an auxiliary tool may increase the explosive forces generated by acupoint-related muscles by stimulating nerves.

scholarly journals Shared internal models for feedforward and feedback control of arm dynamics in non-human primates

2020 ◽  
Author(s):  
Rodrigo S. Maeda ◽  
Rhonda Kersten ◽  
J. Andrew Pruszynski
Keyword(s):  
Feedback Control ◽  
Muscle Activity ◽  
Shoulder Joint ◽  
Feedforward Control ◽  
Neural Mechanisms ◽  
Shoulder Muscle ◽  
Intersegmental Dynamics ◽  
Systematic Reduction ◽  
Elbow Motion ◽  
Feedback Responses

AbstractPrevious work has shown that humans account for and learn novel properties or the arm’s dynamics, and that such learning causes changes in both the predictive (i.e., feedforward) control of reaching and reflex (i.e., feedback) responses to mechanical perturbations. Here we show that similar observations hold in old-world monkeys (macaca fascicularis). Two monkeys were trained to use an exoskeleton to perform a single-joint elbow reaching and to respond to mechanical perturbations that created pure elbow motion. Both of these tasks engaged robust shoulder muscle activity as required to account for the torques that typically arise at the shoulder when the forearm rotates around the elbow joint (i.e., intersegmental dynamics). We altered these intersegmental arm dynamics by having the monkeys generate the same elbow movements with the shoulder joint either free to rotate, as normal, or fixed by the robotic manipulandum, which eliminates the shoulder torques caused by forearm rotation. After fixing the shoulder joint, we found a systematic reduction in shoulder muscle activity. In addition, after releasing the shoulder joint again, we found evidence of kinematic aftereffects (i.e., reach errors) in the direction predicted if failing to compensate for normal arm dynamics. We also tested whether such learning transfers to feedback responses evoked by mechanical perturbations and found a reduction in shoulder feedback responses, as appropriate for these altered arm intersegmental dynamics. Demonstrating this learning and transfer in non-human primates will allow the investigation of the neural mechanisms involved in feedforward and feedback control of the arm’s dynamics.

scholarly journals Atrophy of the supra and infraspinatus muscles due to injury of the suprascapular nerve in horse (sweeny)

2017 ◽  
Vol 24 (1) ◽  
pp. 130-134
Author(s):  
Joandes Henrique Fonteque ◽  
Anderson Fernando De Souza ◽  
Thiago Rinaldi Muller ◽  
Jackson Schade ◽  
Paulo Eduardo Ferian
Keyword(s):  
Case Report ◽  
Nerve Injury ◽  
Muscle Atrophy ◽  
Shoulder Joint ◽  
Clinical Signs ◽  
Suprascapular Nerve ◽  
Santa Catarina ◽  
Shoulder Muscles ◽  
Veterinary Hospital ◽  
Scapular Region

This is a case report of atrophy of the shoulder muscles (sweeny) – supra and infraspinatusdue to suprascapular nerve injury in a horse, cross breed, male, with 15 years of age, weigh350 kg, used for traction, seen at the Veterinary Hospital (HCV) from the Santa Catarina StateUniversity (UDESC), Agroveterinary Sciences Center (CAV) from Lages, SC, Brazil. Theanimal showed clinical signs such as muscle atrophy of the scapular region and moderateinstability of the shoulder joint of the left forelimb. Due to chronic and irreversible changes inthe musculature, with no further complications to the animal, treatment was based onreducing workload and suitability of tack used in the animal. This is the first clinicaldescription in Brazil of atrophy of the supra and infraspinatus muscles due to injury of thesuprascapular nerve with chronic presentation.

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