scholarly journals On the origin of finger enslaving: control with referent coordinates and effects of visual feedback

2020 ◽  
Vol 124 (6) ◽  
pp. 1625-1636 ◽  
Author(s):  
Valters Abolins ◽  
Alex Stremoukhov ◽  
Caroline Walter ◽  
Mark L. Latash
Keyword(s):  
Visual Feedback ◽  
Force Production ◽  
Slow Increase ◽  
Cortical Excitation

We report a consistent slow increase in finger enslaving (force production by noninstructed fingers) when visual feedback was presented on the force produced by either two instructed fingers or two noninstructed fingers of the hand. In contrast, force drifts could be in opposite directions depending on the visual feedback. We interpret enslaving and its drifts at the level of control with referent coordinates for the involved muscles, possibly reflecting spread of cortical excitation.

Intermittency in the Control of Continuous Force Production

2000 ◽  
Vol 84 (4) ◽  
pp. 1708-1718 ◽  
Author(s):  
Andrew B. Slifkin ◽  
David E. Vaillancourt ◽  
Karl M. Newell
Keyword(s):  
Visual Feedback ◽  
Visual Information ◽  
Spectral Power ◽  
Force Production ◽  
Motor Output ◽  
Force Variability ◽  
Force Output ◽  
Feedback Information ◽  
Information Processes ◽  
Feedback Frequency

The purpose of the current investigation was to examine the influence of intermittency in visual information processes on intermittency in the control continuous force production. Adult human participants were required to maintain force at, and minimize variability around, a force target over an extended duration (15 s), while the intermittency of on-line visual feedback presentation was varied across conditions. This was accomplished by varying the frequency of successive force-feedback deliveries presented on a video display. As a function of a 128-fold increase in feedback frequency (0.2 to 25.6 Hz), performance quality improved according to hyperbolic functions (e.g., force variability decayed), reaching asymptotic values near the 6.4-Hz feedback frequency level. Thus, the briefest interval over which visual information could be integrated and used to correct errors in motor output was approximately 150 ms. The observed reductions in force variability were correlated with parallel declines in spectral power at about 1 Hz in the frequency profile of force output. In contrast, power at higher frequencies in the force output spectrum were uncorrelated with increases in feedback frequency. Thus, there was a considerable lag between the generation of motor output corrections (1 Hz) and the processing of visual feedback information (6.4 Hz). To reconcile these differences in visual and motor processing times, we proposed a model where error information is accumulated by visual information processes at a maximum frequency of 6.4 per second, and the motor system generates a correction on the basis of the accumulated information at the end of each 1-s interval.

Timing and visual feedback constraints on repetitive finger force production

2009 ◽  
Vol 201 (4) ◽  
pp. 673-679 ◽  
Author(s):  
Amanda S. Therrien ◽  
Ramesh Balasubramaniam
Keyword(s):  
Visual Feedback ◽  
Force Production ◽  
Finger Force

scholarly journals Force illusions and drifts observed during muscle vibration

2018 ◽  
Vol 119 (1) ◽  
pp. 326-336 ◽  
Author(s):  
Sasha Reschechtko ◽  
Cristian Cuadra ◽  
Mark L. Latash
Keyword(s):  
Visual Feedback ◽  
Force Production ◽  
The Other ◽  
Muscle Vibration ◽  
Finger Force ◽  
Force Perception ◽  
Other Hand ◽  
Referent Coordinate ◽  
Perceived Force ◽  
Frame Set

We explored predictions of a scheme that views position and force perception as a result of measuring proprioceptive signals within a reference frame set by ongoing efferent process. In particular, this hypothesis predicts force illusions caused by muscle vibration and mediated via changes in both afferent and efferent components of kinesthesia. Healthy subjects performed accurate steady force production tasks by pressing with the four fingers of one hand (the task hand) on individual force sensors with and without visual feedback. At various times during the trials, subjects matched the perceived force using the other hand. High-frequency vibration was applied to one or both of the forearms (over the hand and finger extensors). Without visual feedback, subjects showed a drop in the task hand force, which was significantly smaller under the vibration of that forearm. Force production by the matching hand was consistently higher than that of the task hand. Vibrating one of the forearms affected the matching hand in a manner consistent with the perception of higher magnitude of force produced by the vibrated hand. The findings were consistent between the dominant and nondominant hands. The effects of vibration on both force drift and force mismatching suggest that vibration led to shifts in both signals from proprioceptors and the efferent component of perception, the referent coordinate and/or coactivation command. The observations fit the hypothesis on combined perception of kinematic-kinetic variables with little specificity of different groups of peripheral receptors that all contribute to perception of forces and coordinates. NEW & NOTEWORTHY We show that vibration of hand/finger extensors produces consistent errors in finger force perception. Without visual feedback, finger force drifted to lower values without a drift in the matching force produced by the other hand; hand extensor vibration led to smaller finger force drift. The findings fit the scheme with combined perception of kinematic-kinetic variables and suggest that vibration leads to consistent shifts of the referent coordinate and, possibly, of coactivation command to the effector.

Neural correlates of task-related changes in physiological tremor

2013 ◽  
Vol 110 (1) ◽  
pp. 170-176 ◽  
Author(s):  
Christopher M. Laine ◽  
Francesco Negro ◽  
Dario Farina
Keyword(s):  
Motor Unit ◽  
Visual Feedback ◽  
Muscle Force ◽  
Maximum Voluntary Contraction ◽  
Force Production ◽  
The Self ◽  
Frequency Content ◽  
Neural Drive ◽  
Force Tremor ◽  
Command Signals

Appropriate control of muscle contraction requires integration of command signals with sensory feedback. Sensorimotor integration is often studied under conditions in which muscle force is controlled with visual feedback. While it is known that alteration of visual feedback can influence task performance, the underlying changes in neural drive to the muscles are not well understood. In this study, we characterize the frequency content of force fluctuations and neural drive when production of muscle force is target guided versus self guided. In the self-guided condition, subjects performed isometric contractions of the first dorsal interosseous (FDI) muscle while slowly and randomly varying their force level. Subjects received visual feedback of their own force in order to keep contractions between 6% and 10% of maximum voluntary contraction (MVC). In the target-guided condition, subjects used a display of their previously generated force as a target to track over time. During target tracking, force tremor increased significantly in the 3–5 and 7–9 Hz ranges, compared with self-guided contractions. The underlying changes in neural drive were assessed by coherence analysis of FDI motor unit activity. During target-guided force production, pairs of simultaneously recorded motor units showed less coherent activity in the 3–5 Hz frequency range but greater coherence in the 7–9 Hz range than in the self-guided contractions. These results show that the frequency content of common synaptic input to motoneurons is altered when force production is visually guided. We propose that a change in stretch-reflex gain could provide a potential mechanism for the observed changes in force tremor and motor unit coherence.

scholarly journals On the nature of unintentional action: a study of force/moment drifts during multifinger tasks

2016 ◽  
Vol 116 (2) ◽  
pp. 698-708 ◽  
Author(s):  
Behnoosh Parsa ◽  
Daniel J. O'Shea ◽  
Vladimir M. Zatsiorsky ◽  
Mark L. Latash
Keyword(s):  
Visual Feedback ◽  
Sensory Information ◽  
Force Production ◽  
Total Force ◽  
Total Moment ◽  
Individual Finger ◽  
Referent Coordinate ◽  
Force Moment ◽  
Finger Forces ◽  
The Right

We explored the origins of unintentional changes in performance during accurate force production in isometric conditions seen after turning visual feedback off. The idea of control with referent spatial coordinates suggests that these phenomena could result from drifts of the referent coordinate for the effector. Subjects performed accurate force/moment production tasks by pressing with the fingers of a hand on force sensors. Turning the visual feedback off resulted in slow drifts of both total force and total moment to lower magnitudes of these variables; these drifts were more pronounced in the right hand of the right-handed subjects. Drifts in individual finger forces could be in different direction; in particular, fingers that produced moments of force against the required total moment showed an increase in their forces. The force/moment drift was associated with a drop in the index of synergy stabilizing performance under visual feedback. The drifts in directions that changed performance (non-motor equivalent) and in directions that did not (motor equivalent) were of about the same magnitude. The results suggest that control with referent coordinates is associated with drifts of those referent coordinates toward the corresponding actual coordinates of the hand, a reflection of the natural tendency of physical systems to move toward a minimum of potential energy. The interaction between drifts of the hand referent coordinate and referent orientation leads to counterdirectional drifts in individual finger forces. The results also demonstrate that the sensory information used to create multifinger synergies is necessary for their presence over the task duration.

Changes in the force-sharing pattern induced by modifications of visual feedback during force production by a set of fingers

1998 ◽  
Vol 123 (3) ◽  
pp. 255-262 ◽  
Author(s):  
M. L. Latash ◽  
Israel M. Gelfand ◽  
Zong-Ming Li ◽  
Vladimir M. Zatsiorsky
Keyword(s):  
Visual Feedback ◽  
Force Production ◽  
Force Sharing

Effects of Force Requirements on Pinch Force Production in Healthy Adults

Motor Control ◽  
2016 ◽  
Vol 20 (3) ◽  
pp. 299-315 ◽  
Author(s):  
Aisha Khan ◽  
Stacey L. Gorniak
Keyword(s):  
Motor Unit ◽  
Visual Feedback ◽  
Grip Force ◽  
Force Production ◽  
Error Rates ◽  
Visual Signal ◽  
Signal Frequency ◽  
Fine Motor ◽  
Pinch Force ◽  
Motor Unit Firing

Previous studies of fine motor control have focused on the ability of participants to match their grip force production to a visually provided template. We investigated differences exhibited in pinch force control during variable force production templates, including sine-, sawtooth-, and square-wave templates. Our results indicate that increased force requirements are associated with increased error rates and a noisier frequency spectrum, consistent with previous studies. Our results also indicate that visual feedback, in the form of template shape, directly affect pinch force production features and motor unit firing patterns, despite the use of consistent baseline force requirements, amplitude changes, and visual signal frequency. This suggests that CNS modulation of motor unit responses can be triggered by basic changes in visual feedback unrelated to force requirements. The potential implications of error compensation based on this study due to aging are also discussed.

scholarly journals Role of Post-Trial Visual Feedback on Unintentional Force Drift During Isometric Finger Force Production Tasks

Motor Control ◽  
2021 ◽  
pp. 1-14
Author(s):  
S. Balamurugan ◽  
Rachaveti Dhanush ◽  
S.K.M. Varadhan
Keyword(s):  
Visual Feedback ◽  
Maximum Voluntary Contraction ◽  
Control Variable ◽  
Force Production ◽  
Voluntary Contraction ◽  
Central Controller ◽  
The Difference ◽  
Post Trial ◽  
Fingertip Forces

A reduction in fingertip forces during a visually occluded isometric task is called unintentional drift. In this study, unintentional drift was studied for two conditions, with and without “epilogue.” We define epilogue as the posttrial visual feedback in which the outcome of the just-concluded trial is shown before the start of the next trial. For this study, 14 healthy participants were recruited and were instructed to produce fingertip forces to match a target line at 15% maximum voluntary contraction. The results showed a significant reduction in unintentional drift in the epilogue condition. This reduction is probably due to the difference in the shift in λ, the threshold of the tonic stretch reflex, the hypothetical control variable that the central controller can set.

scholarly journals Role of post-trial visual feedback on unintentional force drift during isometric finger force production tasks

2019 ◽  
Author(s):  
S Balamurugan ◽  
Dhanush Rachaveti ◽  
Varadhan SKM
Keyword(s):  
Visual Feedback ◽  
Visual Information ◽  
Force Production ◽  
Finger Force ◽  
Visual Occlusion ◽  
Referent Configuration ◽  
Central Controller ◽  
Post Trial ◽  
Lower Magnitude ◽  
The Right

AbstractForce produced during an isometric finger force production task tends to drift towards a lower magnitude when visual information is occluded. This phenomenon of drift in force without one’s awareness is called unintentional drift. The present study used epilogue, a particular case of post-trial visual feedback, and compared the unintentional drift for two conditions, i.e., with and without the epilogue. For this purpose, fourteen healthy participants were recruited for the experiments and were instructed to produce fingertip forces using four fingers of the right hand with the target line at 15% MVC. A trial lasted for sixteen seconds, where for the initial eight seconds, there is visual feedback followed by the visual occlusion period. The results showed a significant reduction in unintentional drift for the condition involving epilogue when compared to no epilogue. This reduction in drift is due to the shift in the referent configuration parameter by the phenomenon of RC back coupling. Further, we also claim that there might be a distribution of λs or RCs, based on the history of tuning of the control parameter by the central controller. This distribution of λs selected by the central controller in a redundant environment based on the epilogue resulted in a reduction of unintentional drift.

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