scholarly journals Fast-adapting mechanoreceptors are important for force control in precision grip but not for sensorimotor memory

2016 ◽  
Vol 115 (6) ◽  
pp. 3156-3161 ◽  
Author(s):  
Susanna B. Park ◽  
Marco Davare ◽  
Marika Falla ◽  
William R. Kennedy ◽  
Mona M. Selim ◽  
...  
Keyword(s):  
Force Control ◽  
Precision Grip ◽  
Object Manipulation ◽  
Load Force ◽  
Type I ◽  
Tactile Sensitivity ◽  
Latex Gloves ◽  
Variable Weight ◽  
Sensorimotor Memory ◽  
Force Scaling

Sensory feedback from cutaneous mechanoreceptors in the fingertips is important in effective object manipulation, allowing appropriate scaling of grip and load forces during precision grip. However, the role of mechanoreceptor subtypes in these tasks remains incompletely understood. To address this issue, psychophysical tasks that may specifically assess function of type I fast-adapting (FAI) and slowly adapting (SAI) mechanoreceptors were used with object manipulation experiments to examine the regulation of grip force control in an experimental model of graded reduction in tactile sensitivity (healthy volunteers wearing 2 layers of latex gloves). With gloves, tactile sensitivity decreased significantly from 1.9 ± 0.4 to 12.3 ± 2.2 μm in the Bumps task assessing function of FAI afferents but not in a grating orientation task assessing SAI afferents (1.6 ± 0.1 to 1.8 ± 0.2 mm). Six axis force/torque sensors measured peak grip (PGF) and load (PLF) forces generated by the fingertips during a grip-lift task. With gloves there was a significant increase of PGF (14 ± 6%), PLF (17 ± 5%), and grip and load force rates (26 ± 8%, 20 ± 8%). A variable-weight series task was used to examine sensorimotor memory. There was a 20% increase in PGF when the lift of a light object was preceded by a heavy relative to a light object. This relationship was not significantly altered when lifting with gloves, suggesting that the addition of gloves did not change sensorimotor memory effects. We conclude that FAI fibers may be important for the online force scaling but not for the buildup of a sensorimotor memory.

Grip force anticipation of nonlinear, underactuated load force

2021 ◽  
Author(s):  
Francis M. Grover ◽  
Christopher Riehm ◽  
Paula L. Silva ◽  
Tamara Lorenz ◽  
Michael A. Riley
Keyword(s):  
Force Control ◽  
Internal Model ◽  
Grip Force ◽  
Object Manipulation ◽  
Load Force ◽  
Complex Object ◽  
Active Object ◽  
Grip Force Control ◽  
Motor Commands ◽  
Model Approach

Feedforward internal model-based control enabled by efference copies of motor commands is the prevailing theoretical account of motor anticipation. Grip force control during object manipulation-a paradigmatic example of motor anticipation-is a key line of evidence for that account. However, the internal model approach has not addressed the computational challenges faced by the act of manipulating mechanically complex objects with nonlinear, underactuated degrees of freedom. These objects exhibit complex and unpredictable load force dynamics which cannot be encoded by efference copies of underlying motor commands, leading to the prediction from the perspective of an efference copy-enabled feedforward control scheme that grip force should either lag or fail to coordinate with changes in load force. In contrast to that prediction, we found evidence for strong, precise, anticipatory grip force control during manipulations of a complex object. The results are therefore inconsistent with the internal forward model approach and suggest that efference copies of motor commands are not necessary to enable anticipatory control during active object manipulation.

scholarly journals Proximal arm kinematics affect grip force-load force coordination

2015 ◽  
Vol 114 (4) ◽  
pp. 2265-2277 ◽  
Author(s):  
Billy C. Vermillion ◽  
Peter S. Lum ◽  
Sang Wook Lee
Keyword(s):  
Force Control ◽  
Muscle Activation ◽  
Grip Force ◽  
Object Manipulation ◽  
Load Force ◽  
Hand Muscles ◽  
Grip Force Control ◽  
Arm Kinematics ◽  
Force Ratio ◽  
The Impact

During object manipulation, grip force is coordinated with load force, which is primarily determined by object kinematics. Proximal arm kinematics may affect grip force control, as proximal segment motion could affect control of distal hand muscles via biomechanical and/or neural pathways. The aim of this study was to investigate the impact of proximal kinematics on grip force modulation during object manipulation. Fifteen subjects performed three vertical lifting tasks that involved distinct proximal kinematics (elbow/shoulder), but resulted in similar end-point (hand) trajectories. While temporal coordination of grip and load forces remained similar across the tasks, proximal kinematics significantly affected the grip force-to-load force ratio ( P = 0.042), intrinsic finger muscle activation ( P = 0.045), and flexor-extensor ratio ( P < 0.001). Biomechanical coupling between extrinsic hand muscles and the elbow joint cannot fully explain the observed changes, as task-related changes in intrinsic hand muscle activation were greater than in extrinsic hand muscles. Rather, between-task variation in grip force (highest during task 3) appears to contrast to that in shoulder joint velocity/acceleration (lowest during task 3). These results suggest that complex neural coupling between the distal and proximal upper extremity musculature may affect grip force control during movements, also indicated by task-related changes in intermuscular coherence of muscle pairs, including intrinsic finger muscles. Furthermore, examination of the fingertip force showed that the human motor system may attempt to reduce variability in task-relevant motor output (grip force-to-load force ratio), while allowing larger fluctuations in output less relevant to task goal (shear force-to-grip force ratio).

Grip and load force control and coordination in object manipulation during a night of sleep deprivation

2014 ◽  
Vol 13 (2) ◽  
pp. 163-171 ◽  
Author(s):  
Sabrina Tiago Pedão ◽  
Stefane Aline Aguiar ◽  
Bianca Pinto Cunha ◽  
Paulo Barbosa de Freitas
Keyword(s):  
Sleep Deprivation ◽  
Force Control ◽  
Object Manipulation ◽  
Load Force

Adaptive control of grip force to compensate for static and dynamic torques during object manipulation

2011 ◽  
Vol 106 (6) ◽  
pp. 2973-2981 ◽  
Author(s):  
F. Crevecoeur ◽  
T. Giard ◽  
J.-L. Thonnard ◽  
P. Lefèvre
Keyword(s):  
Grip Force ◽  
Opposite Effect ◽  
Visual Target ◽  
Center Of Mass ◽  
Precision Grip ◽  
Object Manipulation ◽  
Grip Force Control ◽  
Slow Adaptation ◽  
The Moment ◽  
Force Scaling

Manipulating a cup by the handle requires compensating for the torque induced by the moment of the mass of the cup relative to the location of the handle. In the present study, we investigated the control strategy of subjects asked to perform grip-lift movements with an object with center of mass located away from the grip axis. Participants were asked to lift the manipulandum with a two-fingers precision grip and stabilize it in front of a visual target. Subjects showed a gradual and slow adaptation of the grip-force scaling across trials: the grip force tended to decrease slowly, and the temporal coordination between grip-force and load-torque rates displayed gradually, better-coordinated patterns. Importantly, this adaptation was much slower than the stabilization of the same parameters measured either when no torque came into play or after previous adaptation to the presence of a torque. In contrast, the maximum rotation induced by the torque was controlled efficiently after only few trials, and an unexpected decrease in the tangential torque produced significant overcompensation. An unexpected increase in torque produced a consistent opposite effect. This shows that the compensation for the dynamic torque was based on an anticipatory, dynamic counter-torque produced by the arm and wrist motor commands. The comparatively slow stabilization of grip-force control suggests a specific adaptation process engaged by the presence of the torque. This paradigm, including tangential torques, clearly constitutes a powerful tool to extract the adaptive component of grip control during object manipulation.

Anticipatory and Reactive Grip Force Control in Patients with Alzheimer’s Disease: A Pilot Study

2021 ◽  
pp. 1-15
Author(s):  
Anna Gabriel ◽  
Carolin T. Lehner ◽  
Chiara Höhler ◽  
Thomas Schneider ◽  
Tessa P.T. Pfeiffer ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Pilot Study ◽  
Force Control ◽  
Grip Force ◽  
Object Manipulation ◽  
Step Test ◽  
Grip Force Control ◽  
Potential Biomarker ◽  
Neurological Conditions

Background: Alzheimer’s disease (AD) affects several cognitive functions and causes altered motor function. Fine motor deficits during object manipulation are evident in other neurological conditions, but have not been assessed in dementia patients yet. Objective: Investigate reactive and anticipatory grip force control in response to unexpected and expected load force perturbation in AD. Methods: Reactive and anticipatory grip force was investigated using a grip-device with force sensors. In this pilot study, fifteen AD patients and fourteen healthy controls performed a catching task. They held the device with one hand while a sandbag was dropped into an attached receptacle either by the experimenter or by the participant. Results: In contrast to studies of other neurological conditions, the majority of AD patients exerted lower static grip force levels than controls. Interestingly, patients who were slow in the Luria’s three-step test produced normal grip forces. The timing and magnitude of reactive grip force control were largely preserved in patients. In contrast, timing and extent of anticipatory grip forces were impaired in patients, although anticipatory control was generally preserved. These deficits were correlated with decreasing Mini-Mental State Examination scores. Apraxia scores, assessed by pantomime of tool-use, did not correlate with performance in the catching task. Conclusion: We interpreted the decreased grip force in AD in the context of loss of strength and lethargy, typical for patients with AD. The lower static grip force during object manipulation may emerge as a potential biomarker for early stages of AD, but more studies with larger sample sizes are necessary.

Deficits of predictive grip force control during object manipulation in acute stroke

2003 ◽  
Vol 250 (7) ◽  
pp. 850-860 ◽  
Author(s):  
Dennis A. Nowak ◽  
Joachim Hermsd�rfer ◽  
Helge Topka
Keyword(s):  
Acute Stroke ◽  
Force Control ◽  
Grip Force ◽  
Object Manipulation ◽  
Grip Force Control

Variable and intermittent grip force control in response to differing load force dynamics

2018 ◽  
Vol 237 (3) ◽  
pp. 687-703 ◽  
Author(s):  
Francis M. Grover ◽  
Patrick Nalepka ◽  
Paula L. Silva ◽  
Tamara Lorenz ◽  
Michael A. Riley
Keyword(s):  
Force Control ◽  
Grip Force ◽  
Load Force ◽  
Force Dynamics ◽  
Grip Force Control

Wrist Action Affects Precision Grip Force

1997 ◽  
Vol 78 (1) ◽  
pp. 271-280 ◽  
Author(s):  
Mary M. Werremeyer ◽  
Kelly J. Cole
Keyword(s):  
Grip Force ◽  
Precision Grip ◽  
Load Force ◽  
Myoelectric Activity ◽  
Resistive Load ◽  
Wrist Flexion ◽  
Wrist Extension ◽  
Hand Muscles ◽  
Force Pulse ◽  
Grasp Stability

Werremeyer, Mary M. and Kelly J. Cole. Wrist action affects precision grip force. J. Neurophysiol. 78: 271–280, 1997. When moving objects with a precision grip, fingertip forces normal to the object surface (grip force) change in parallel with forces tangential to the object (load force). We investigated whether voluntary wrist actions can affect grip force independent of load force, because the extrinsic finger muscles cross the wrist. Grip force increased with wrist angular speed during wrist motion in the horizontal plane, and was much larger than the increased tangential load at the fingertips or the reaction forces from linear acceleration of the test object. During wrist flexion the index finger muscles in the hand and forearm increased myoelectric activity; during wrist extension this myoelectric activity increased little, or decreased for some subjects. The grip force maxima coincided with wrist acceleration maxima, and grip force remained elevated when subjects held the wrist in extreme flexion or extension. Likewise, during isometric wrist actions the grip force increased even though the fingertip loads remained constant. A grip force “pulse” developed that increased with wrist force rate, followed by a static grip force while the wrist force was sustained. Subjects could not suppress the grip force pulse when provided visual feedback of their grip force. We conclude that the extrinsic hand muscles can be recruited to assist the intended wrist action, yielding higher grip-load ratios than those employed with the wrist at rest. This added drive to hand muscles overcame any loss in muscle force while the extrinsic finger flexors shortened during wrist flexion motion. During wrist extension motion grip force increases apparently occurred from eccentric contraction of the extrinsic finger flexors. The coactivation of hand closing muscles with other wrist muscles also may result in part from a general motor facilitation, because grip force increased during isometric knee extension. However, these increases were related weakly to the knee force. The observed muscle coactivation, from all sources, may contribute to grasp stability. For example, when transporting grasped objects, upper limb accelerations simultaneously produce inertial torques at the wrist that must be resisted, and inertial loads at the fingertips from the object that must be offset by increased grip force. The muscle coactivation described here would cause similarly timed pulses in the wrist force and grip force. However, grip-load coupling from this mechanism would not contribute much to grasp stability when small wrist forces are required, such as for slow movements or when the object's total resistive load is small.

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