scholarly journals Task-dependent modulation of spinal and transcortical stretch reflexes linked to motor learning rate

2017 ◽  
Author(s):  
Michael Dimitriou
Keyword(s):  
Motor Learning ◽  
Conflict Of Interest ◽  
Learning Performance ◽  
Monosynaptic Reflex ◽  
Reflex Response ◽  
Level Control ◽  
Visuomotor Rotation ◽  
Stretch Reflexes ◽  
Visuomotor Task ◽  
Long Latency

AbstractIt is generally believed that task-dependent control of body configuration (‘posture’) is achieved by adjusting voluntary motor activity and transcortical ‘long-latency’ reflexes. Spinal monosynaptic circuits are thought not to be engaged in such task-level control. Similarly, being in a state of motor learning has been strongly associated only with an upregulation of feedback responses at transcortical latencies and beyond. In two separate experiments, the current study examined the task-dependent modulation of stretch reflexes by perturbing the hand of human subjects while they were waiting for a ‘Go’ signal to move at the different stages of a classic kinematic learning task (visuomotor rotation). Although the subjects had to resist all haptic perturbations equally, the study leveraged that task-dependent feedback controllers may already be ’loaded’ at the movement anticipation stage. In addition to an upregulation of short- and long-latency reflex gains during early exposure to the visual distortion, I found a relative inhibition of reflex responses in the ‘washout’ stage (sensory realignment state). For more distal muscles (brachioradialis), this inhibition also extended to the monosynaptic reflex response (‘R1’). These R1 gains reflected individual motor learning performance in the visuomotor task. The results demonstrate that the system’s ‘control policy’ in visuomotor adaptation can also include inhibition of proprioceptive reflexes, and that aspects of this policy can affect monosynaptic spinal circuits. The latter finding suggests a novel form of state-related control, probably realized by independent control of fusimotor neurons, through which segmental circuits can tune to higher-level features of a sensorimotor task.Additional InformationConflict of interestThe author declares no conflict of interest.Author contributionsM.D. devised, designed and implemented the project, analyzed the data and wrote the manuscript. The author approves the final version of the manuscript and is fully accountable for all aspects of the work. The experiments were performed at the Department of Integrative Medical Biology, Umeå University, Sweden.FundingThis work was financially supported through grants awarded to M.D. by the Kempe Foundation, the local Foundation for Medical Research (“Insamlingsstiftelsen”) and the Swedish Research Council (project 2016-02237).

Review of Motor Learning & Performance: From Principles to Practice.

1993 ◽  
Vol 38 (12) ◽  
pp. 1336-1336
Author(s):  
Terri Gullickson ◽  
Pamela Ramser
Keyword(s):  
Motor Learning ◽  
Learning Performance

scholarly journals MONOSYNAPTIC REFLEX RESPONSE OF INDIVIDUAL MOTONEURONS AS A FUNCTION OF FREQUENCY

1957 ◽  
Vol 40 (3) ◽  
pp. 435-450 ◽  
Author(s):  
David P. C. Lloyd
Keyword(s):  
High Frequency ◽  
Temporal Summation ◽  
Low Frequency ◽  
Stimulation Frequency ◽  
Monosynaptic Reflex ◽  
Reflex Response ◽  
High Frequency Stimulation ◽  
Low Frequency Stimulation ◽  
Frequency Stimulation ◽  
Frequency Of Stimulation

An assemblage of individual motoneurons constituting a synthetic motoneuron pool has been studied from the standpoint of relating monosynaptic reflex responses to frequency of afferent stimulation. Intensity of low frequency depression is not a simple function of transmitter potentiality. As frequency of stimulation increases from 3 per minute to 10 per second, low frequency depression increases in magnitude. Between 10 and approximately 60 per second low frequency depression apparently diminishes and subnormality becomes a factor in causing depression. At frequencies above 60 per second temporal summation occurs, but subnormality limits the degree of response attainable by summation. At low stimulation frequencies rhythm is determined by stimulation frequency. Interruptions of rhythmic firing depend solely upon temporal fluctuation of excitability. At high frequency of stimulation rhythm is determined by subnormality rather than inherent rhythmicity, and excitability fluctuation leads to instability of response rhythm. In short, whatever the stimulation frequency, random excitability fluctuation is the factor disrupting rhythmic response. Monosynaptic reflex response latency is stable during high frequency stimulation as it is in low frequency stimulation provided a significant extrinsic source of random bombardment is not present. In the presence of powerful random bombardment discharge may become random with respect to monosynaptic afferent excitation provided the latter is feeble. When this occurs it does so equally at low frequency and high frequency. Thus temporal summation is not a necessary factor. There is, then, no remaining evidence to suggest that the agency for temporal summation in the monosynaptic system becomes a transmitting agency in its own right.

Reflex Responses Induced by Tooth Unloading

2000 ◽  
Vol 84 (2) ◽  
pp. 1088-1092 ◽  
Author(s):  
Kemal S. Türker ◽  
Melissa Jenkins
Keyword(s):  
Local Anesthetic ◽  
Muscle Activity ◽  
Masseter Muscle ◽  
Horizontal Direction ◽  
Reflex Response ◽  
Maxillary Incisor ◽  
Static Force ◽  
Incisor Tooth ◽  
Long Latency ◽  
Unloading Reflex

The reflex response of the masseter muscle to the rapid unloading of a single maxillary incisor tooth was studied. Unloading of a static force of 2 N in the horizontal direction resulted in a short-latency excitation, inhibition, and long-latency excitation of masseter muscle activity occurring at latencies of approximately 13, 20, and 40 ms, respectively, with a corresponding change in bite force occurring slightly later in each case. Following the blocking of periodontal input by the injection of local anesthetic around the stimulated tooth, inhibitory responses were abolished. Therefore, it is concluded that the observed masseteric inhibition was caused by the unloading of periodontal mechanoreceptors and thus that these receptors may contribute to the jaw unloading reflex.

scholarly journals Motor learning and transfer: from feedback to feedforward control

2019 ◽  
Author(s):  
Rodrigo S. Maeda ◽  
Paul L. Gribble ◽  
J. Andrew Pruszynski
Keyword(s):  
Motor Learning ◽  
Muscle Activity ◽  
Shoulder Joint ◽  
Stretch Reflex ◽  
Feedforward Control ◽  
Motor Task ◽  
Joint Torques ◽  
Motor Commands ◽  
Shoulder Muscle ◽  
Long Latency

AbstractPrevious work has demonstrated that when learning a new motor task, the nervous system modifies feedforward (ie. voluntary) motor commands and that such learning transfers to fast feedback (ie. reflex) responses evoked by mechanical perturbations. Here we show the inverse, that learning new feedback responses transfers to feedforward motor commands. Sixty human participants (34 females) used a robotic exoskeleton and either 1) received short duration mechanical perturbations (20 ms) that created pure elbow rotation or 2) generated self-initiated pure elbow rotations. They did so with the shoulder joint free to rotate (normal arm dynamics) or locked (altered arm dynamics) by the robotic manipulandum. With the shoulder unlocked, the perturbation evoked clear shoulder muscle activity in the long-latency stretch reflex epoch (50-100ms post-perturbation), as required for countering the imposed joint torques, but little muscle activity thereafter in the so-called voluntary response. After locking the shoulder joint, which alters the required joint torques to counter pure elbow rotation, we found a reliable reduction in the long-latency stretch reflex over many trials. This reduction transferred to feedforward control as we observed 1) a reduction in shoulder muscle activity during self-initiated pure elbow rotation trials and 2) kinematic errors (ie. aftereffects) in the direction predicted when failing to compensate for normal arm dynamics, even though participants never practiced self-initiated movements with the shoulder locked. Taken together, our work shows that transfer between feedforward and feedback control is bidirectional, furthering the notion that these processes share common neural circuits that underlie motor learning and transfer.

scholarly journals Neural Excursions from Low-Dimensional Manifold Structure Explain Intersubject Variation in Human Motor Learning

2021 ◽  
Author(s):  
Corson N Areshenkoff ◽  
Daniel J Gale ◽  
Joe Y Nashed ◽  
Dominic Standage ◽  
John Randall Flanagan ◽  
...  
Keyword(s):  
Motor Learning ◽  
Large Scale ◽  
Brain Activity ◽  
Dimensional Subspace ◽  
Learning Performance ◽  
Dimensional Manifold ◽  
Learning Abilities ◽  
Manifold Structure ◽  
Electrophysiological Studies ◽  
Low Dimensional

Humans vary greatly in their motor learning abilities, yet little is known about the neural mechanisms that underlie this variability. Recent neuroimaging and electrophysiological studies demonstrate that large-scale neural dynamics inhabit a low-dimensional subspace or manifold, and that learning is constrained by this intrinsic manifold architecture. Here we asked, using functional MRI, whether subject-level differences in neural excursion from manifold structure can explain differences in learning across participants. We had subjects perform a sensorimotor adaptation task in the MRI scanner on two consecutive days, allowing us to assess their learning performance across days, as well as continuously measure brain activity. We find that the overall neural excursion from manifold activity in both cognitive and sensorimotor brain networks is associated with differences in subjects' patterns of learning and relearning across days. These findings suggest that off-manifold activity provides an index of the relative engagement of different neural systems during learning, and that intersubject differences in patterns of learning and relearning across days are related to reconfiguration processes in cognitive and sensorimotor networks during learning.

Sensorimotor knowledge from task-irrelevant feedback contributes to motor learning

2021 ◽  
Author(s):  
Wanying Jiang ◽  
Yajie Liu ◽  
Yuqing Bi ◽  
Kunlin Wei
Keyword(s):  
Motor Learning ◽  
Perceptual Learning ◽  
Implicit Learning ◽  
Motor Adaptation ◽  
Strategic Learning ◽  
Visuomotor Rotation ◽  
Saving Effect ◽  
Sensorimotor Knowledge ◽  
Sensory Processes ◽  
Task Irrelevant

Exposure to task-irrelevant feedback leads to perceptual learning, but its effect on motor learning has been understudied. Here we asked human participants to reach a visual target with a hand-controlled cursor while observing another cursor moving independently in a different direction. While the task-irrelevant feedback did not change the main task's performance, it elicited robust savings in subsequent adaptation to classical visuomotor rotation perturbation. We demonstrated that the saving effect resulted from a faster formation of strategic learning through a series of experiments, not from gains in the implicit learning process. Furthermore, the saving effect was robust against drastic changes in stimulus features (i.e., rotation size or direction) or task types (i.e., for motor adaptation and skill learning). However, the effect was absent when the task-irrelevant feedback did not carry the visuomotor relationship embedded in visuomotor rotation. Thus, though previous research on perceptual learning has related task-irrelevant feedback to changes in early sensory processes, our findings support its role in acquiring abstract sensorimotor knowledge during motor learning. Motor learning studies have traditionally focused on task-relevant feedback, but our study extends the scope of feedback processes and sheds new light on the dichotomy of explicit and implicit learning in motor adaptation as well as motor structure learning.

scholarly journals Stabilizing stretch reflexes are modulated independently from the rapid release of perturbation-triggered motor plans

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Hyunglae Lee ◽  
Eric J. Perreault
Keyword(s):  
Motor Response ◽  
Spinal Reflexes ◽  
Reflex Response ◽  
Voluntary Activity ◽  
Motor Responses ◽  
Triggered Reaction ◽  
Triggered Reactions ◽  
Long Latency ◽  
Target Effect ◽  
Long Latency Reflex

Abstract Responses elicited after the shortest latency spinal reflexes but prior to the onset of voluntary activity can display sophistication beyond a stereotypical reflex. Two distinct behaviors have been identified for these rapid motor responses, often called long-latency reflexes. The first is to maintain limb stability by opposing external perturbations. The second is to quickly release motor actions planned prior to the disturbance, often called a triggered reaction. This study investigated their interaction when motor tasks involve both limb stabilization and motor planning. We used a robotic manipulator to change the stability of the haptic environment during 2D arm reaching tasks, and to apply perturbations that could elicit rapid motor responses. Stabilizing reflexes were modulated by the orientation of the haptic environment (field effect) whereas triggered reactions were modulated by the target to which subjects were instructed to reach (target effect). We observed that there were no significant interactions between the target and field effects in the early (50–75 ms) portion of the long-latency reflex, indicating that these components of the rapid motor response are initially controlled independently. There were small but significant interactions for two of the six relevant muscles in the later portion (75–100 ms) of the reflex response. In addition, the target effect was influenced by the direction of the perturbation used to elicit the motor response, indicating a later feedback correction in addition to the early component of the triggered reaction. Together, these results demonstrate how distinct components of the long-latency reflex can work independently and together to generate sophisticated rapid motor responses that integrate planning with reaction to uncertain conditions.

Optimal Variability for Effective Motor Learning

2019 ◽  
Author(s):  
Jürgen Birklbauer
Keyword(s):  
Motor Learning ◽  
Focal Point ◽  
Contextual Interference ◽  
Learning Performance ◽  
Practical Training ◽  
Movement Variability ◽  
Theoretical Concepts ◽  
Beneficial Effects ◽  
Differential Learning ◽  
Variable Practice

This thesis addresses different manifestations and practical implementations of movement variability in respect to their beneficial effects on movement coordination and learning. The focal point of this topic is formed by the comparison between the contextual interference paradigm and the differential learning approach, representing two variable practice strategies found to improve motor learning performance under certain conditions. The theoretical backgrounds and empirical findings of each approach are thoroughly reviewed in the first part of this work. These theoretical concepts, and their resultant practical training approaches, arrive at the notion of an optimal magnitude and structure of movement variability that should be encouraged during practice. The second part of this work presents a parallelgroup study designed to contrast the effects of a high contextual interference and schema-based practice regime with two variants of differential training on the adoption of two indoor hockey skills in beginners.

The comparison of motor learning performance with and without feedback

2012 ◽  
Vol 29 (3) ◽  
pp. 103-110 ◽  
Author(s):  
Abbas Orand ◽  
Junichi Ushiba ◽  
Yutaka Tomita ◽  
Satoashi Honda
Keyword(s):  
Motor Learning ◽  
Learning Performance
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