scholarly journals Visually-updated hand state estimates modulate the proprioceptive reflex independently of motor task requirements

eLife ◽  
2020 ◽  
Vol 9 ◽  
Author(s):  
Sho Ito ◽  
Hiroaki Gomi
Keyword(s):  
Stretch Reflex ◽  
Muscle Activation ◽  
Motor Task ◽  
Proprioceptive Information ◽  
Motor Tasks ◽  
Stretch Reflexes ◽  
Motor Mapping ◽  
Task Requirements ◽  
Multimodal Information ◽  
Proprioceptive Reflex

Fast signaling from vision and proprioception to muscle activation plays essential roles in quickly correcting movement. Though many studies have demonstrated modulation of the quick sensorimotor responses as depending on context in each modality, the contribution of multimodal information has not been established. Here, we examined whether state estimates contributing to stretch reflexes are represented solely by proprioceptive information or by multimodal information. Unlike previous studies, we newly found a significant stretch-reflex attenuation by the distortion and elimination of visual-feedback without any change in motor tasks. Furthermore, the stretch-reflex amplitude reduced with increasing elimination durations which would degrade state estimates. By contrast, even though a distortion was introduced in the target-motor-mapping, the stretch reflex was not simultaneously attenuated with visuomotor reflex. Our results therefore indicate that the observed stretch-reflex attenuation is specifically ascribed to uncertainty increase in estimating hand states, suggesting multimodal contributions to the generation of stretch reflexes.

Measuring poststroke spasticity

2000 ◽  
Vol 10 (1) ◽  
pp. 69-74 ◽  
Author(s):  
J. M. Gregson ◽  
A. K. Sharma
Keyword(s):  
Normal State ◽  
Stretch Reflex ◽  
Muscle Activation ◽  
Muscle Tone ◽  
Clinical Syndrome ◽  
Motor Disorder ◽  
Muscle Forces ◽  
Joint Movement ◽  
Stretch Reflexes ◽  
Reflex Action

What is spasticity?Spasticity is a well-recognized and potentially important clinical syndrome comprising inappropriate and involuntary high muscle tone. It has been variably defined, with debate still ongoing. Currently, the most widely accepted definition is that of Lance, stating that spasticity is ‘a motor disorder characterized by a velocity-dependent increase in tonic stretch reflexes (muscle tone) with exaggerated tendon jerks, resulting from hyper-excitability of the stretch reflex.’ Unfortunately, even this description does not fully encompass the multifactorial nature of spasticity, since resistance to movement, even in the normal state, is subject to varied contributors. These include patient volition, inertia, visco-elastic muscle forces and range of joint movement, as well as true muscle activation secondary to reflex action. In the real clinical world, it is often not possible to distinguish which of these features is/are dominant. Furthermore, spastic muscle undergoes physiopathological, rheologic change with stiffness, atrophy, fibrosis and finally contracture.

scholarly journals The influence of startReact on long-latency reflexive muscle activation during the transition from posture to movement

2017 ◽  
Author(s):  
Claire F. Honeycutt ◽  
Vengateswaran J. Ravichandran ◽  
Eric J. Perreault
Keyword(s):  
Muscle Activity ◽  
Stretch Reflex ◽  
Muscle Activation ◽  
Strong Influence ◽  
Time Window ◽  
Motor Tasks ◽  
Motor Pathways ◽  
Long Latency ◽  
Startreact Effect ◽  
The Continuum

AbstractMany motor tasks involve transitions from posture to movement such as shifting from holding an object to setting it on a surface. Although many movements are voluntary processes, they are facilitated through motor pathways that span the continuum between reflexive and voluntary control. The mechanisms driving the long-latency stretch reflex (LLSR) have remained hotly contested. Recently, startReact has been shown to influence the fast muscular response to perturbations (Ravichandran et. al. 2013). The objective of this study was to evaluate how the LLSR and startReact impact the muscular response during the transition from posture to movement. We hypothesized that both the LLSR and startReact would be involved throughout the transition from posture to movement; however there would be a clear transition from LLSR dominance during posture to startReact dominance near/during movement. We tested this hypothesis using perturbations of elbow posture at various times before a fast ballistic extension movement. We found clear evidence that both the LLSR and startReact components were influenced changes in the late long-latency time window. The results provide insights on how the nervous system regulates involuntary responses to perturbations during the transition from maintenance of arm posture to movement.New and NoteworthyWe recently demonstrated that the startReact effect, the startled release of a planned movement, can influence the muscular response during the LLSR. Here we observe how the influence of startReact can change from the transition from posture (no/little influence) to movement (strong influence). While not all paradigms trigger a startReact effect, this work demonstrates that when present startRect can have a profound effect on the overall muscle activity - even obscuring the traditional LLSR response.

scholarly journals Contributions of Altered Stretch Reflex Coordination to Arm Impairments Following Stroke

2010 ◽  
Vol 104 (6) ◽  
pp. 3612-3624 ◽  
Author(s):  
Randy D. Trumbower ◽  
Vengateswaran J. Ravichandran ◽  
Matthew A. Krutky ◽  
Eric J. Perreault
Keyword(s):  
Stretch Reflex ◽  
Muscle Activation ◽  
Motor Impairment ◽  
Load Condition ◽  
Elbow Flexion ◽  
Control Group ◽  
Stretch Reflexes ◽  
Reflex Pathways ◽  
Stroke Group ◽  
Arm Function

Patterns of stereotyped muscle coactivation, clinically referred to as synergies, emerge following stroke and impair arm function. Although researchers have focused on cortical contributions, there is growing evidence that altered stretch reflex pathways may also contribute to impairment. However, most previous reflex studies have focused on passive, single-joint movements without regard to their coordination during volitional actions. The purpose of this study was to examine the effects of stroke on coordinated activity of stretch reflexes elicited in multiple arm muscles following multijoint perturbations. We hypothesized that cortical injury results in increased stretch reflexes of muscles characteristic of the abnormal flexor synergy during active arm conditions. To test this hypothesis, we used a robot to apply position perturbations to impaired arms of 10 stroke survivors and dominant arms of 8 healthy age-matched controls. Corresponding reflexes were assessed during volitional contractions simulating different levels of gravitational support, as well as during voluntary flexion and extension of the elbow and shoulder. Reflexes were quantified by average rectified surface electromyogram, recorded from eight muscles spanning the elbow and shoulder. Reflex coordination was quantified using an independent components analysis. We found stretch reflexes elicited in the stroke group were significantly less sensitive to changes in background muscle activation compared with those in the control group ( P < 0.05). We also observed significantly increased reflex coupling between elbow flexor and shoulder abductor–extensor muscles in stroke subjects relative to that in control subjects. This increased coupling was present only during volitional tasks that required elbow flexion ( P < 0.001), shoulder extension ( P < 0.01), and gravity opposition ( P < 0.01), but not during the “no load” condition. During volitional contractions, reflex amplitudes scaled with the level of impairment, as assessed by Fugl-Meyer scores ( r2 = 0.63; P < 0.05). We conclude that altered reflex coordination is indicative of motor impairment level and may contribute to impaired arm function following stroke.

Statistical Considerations When Assessing Short Latency Stretch Reflexes in the Human Soleus Muscle

Motor Control ◽  
2015 ◽  
Vol 19 (4) ◽  
pp. 253-270 ◽  
Author(s):  
Asger Roer Pedersen ◽  
Peter William Stubbs ◽  
Jørgen Feldbæk Nielsen
Keyword(s):  
Ankle Joint ◽  
Soleus Muscle ◽  
Stretch Reflex ◽  
Short Latency ◽  
Response Magnitude ◽  
Variance Heterogeneity ◽  
Stretch Reflexes ◽  
Response Characteristics ◽  
Normally Distributed

The aim was to investigate trial-by-trial response characteristics in the short-latency stretch reflex (SSR). Fourteen dorsiflexion stretches were applied to the ankle joint with a precontracted soleus muscle on 2 days. The magnitude and variability of trial-by-trial responses of the SSR were assessed. The SSR was log-normally distributed and variance heterogeneous between subjects. For some subjects, the magnitude and variance differed between days and stretches. As velocity increased, variance heterogeneity tended to decrease and response magnitude increased. The current study demonstrates the need to assess trial-by-trial response characteristics and not averaged curves. Moreover, it provides an analysis of SSR characteristics accounting for log-normally distributed and variance heterogeneous trial-by-trial responses.

Combination of musculoskeletal and wear models to investigate the effect of daily living activities on wear of hip prostheses

2021 ◽  
Vol 235 (12) ◽  
pp. 2675-2687
Author(s):  
Lorenza Mattei ◽  
Matilde Tomasi ◽  
Alessio Artoni ◽  
Enrico Ciulli ◽  
Francesca Di Puccio
Keyword(s):  
Motor Task ◽  
Analysis Data ◽  
Daily Activities ◽  
Wear Depth ◽  
Motor Tasks ◽  
Hip Prostheses ◽  
Wear Modelling ◽  
Sporting Activities ◽  
Joint Prostheses ◽  
Hip Arthroplasties

Abstract Numerical wear predictions are gaining increasing interest in many engineering applications, as they allow to simulate complex operative conditions not easily replicable in the laboratory. As far as hip prostheses are concerned, most of the wear models in the literature are based on the simulation of gait (recommended also in experimental wear tests), since gait is considered the most frequent and important motor task to recover after arthroplasty. However, since joint prostheses have been increasingly implanted in younger people, high loads and potentially severe conditions, e.g. due to sporting activities, should also be considered for a more reliable wear assessment of these implants. In this study, we propose a profitable combination of musculoskeletal and analytical wear modelling for the prediction of wear caused by common daily activities in metal-on-plastic hip arthroplasties. Several motion analysis data available in the literature (walking, fast walking, lunge, squat, stair negotiation) were selected and the effects of such motor tasks on prosthesis wear were investigated, both separately and in combination. Additionally, for comparative purposes, wear prediction for simplified gait conditions prescribed by the ISO 14242 standard, were also considered. Results suggest that this latter case produces lower wear depth and volume with respect to a relatively demanding combination of the selected daily activities. The preliminary results of the present study represent a first step towards the auspicious goal of validating the proposed procedure for in silico trials of hip arthroplasties.

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.

Assessing multiple muscle activation during squat movements with different loading conditions – an EMG study

2018 ◽  
Vol 63 (4) ◽  
pp. 413-420
Author(s):  
Amir Pourmoghaddam ◽  
Marius Dettmer ◽  
Stefany J.K. Malanka ◽  
Mitchell Veverka ◽  
Daniel P. O’Connor ◽  
...  
Keyword(s):  
Repeated Measures ◽  
Muscle Activation ◽  
Linear Analysis ◽  
Clinical Diagnostics ◽  
Analysis Tool ◽  
Loading Conditions ◽  
Motor Tasks ◽  
Cyclic Movements ◽  
Non Linear ◽  
Clinical Environments

Abstract Surface electromyography (EMG) is a valuable tool in clinical diagnostics and research related to human neuromotor control. Non-linear analysis of EMG data can help with detection of subtle changes of control due to changes of external or internal constraints during motor tasks. However, non-linear analysis is complex and results may be difficult to interpret, particularly in clinical environments. We developed a non-linear analysis tool (SYNERGOS) that evaluates multiple muscle activation (MMA) features and provides a single value for description of activation characteristics. To investigate the responsiveness of SYNERGOS to kinetic changes during cyclic movements, 13 healthy young adults performed squat movements under different loading conditions (100%–120% of body weight). We processed EMG data to generate SYNERGOS indices and used two-way repeated measures ANOVA to determine changes of MMA in response to loading conditions during movement. SYNERGOS values were significantly different for each loading condition. We concluded that the algorithm is sensitive to kinetic changes during cyclic movements, which may have implications for applications in a variety of experimental and diagnostic settings.

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