scholarly journals Flexible organization of grip force control during movement frequency scaling

2019 ◽  
Vol 122 (6) ◽  
pp. 2304-2315
Author(s):  
Francis M. Grover ◽  
Sarah M. Schwab ◽  
Paula L. Silva ◽  
Tamara Lorenz ◽  
Michael A. Riley
Keyword(s):  
Force Control ◽  
Grip Force ◽  
Sagittal Plane ◽  
Oscillation Amplitude ◽  
Load Force ◽  
Force Load ◽  
Grip Force Control ◽  
Force Coupling ◽  
Tightly Coupled ◽  
Oscillation Frequencies

The grip force applied to maintain grasp of a handheld object has been typically reported as tightly coupled to the load force exerted by the object as it is actively manipulated, occurring proportionally and consistently in phase with changes in load force. However, continuous grip force-load force coupling breaks down when overall load force levels and oscillation amplitudes are lower (Grover F, Lamb M, Bonnette S, Silva PL, Lorenz T, Riley MA. Exp Brain Res 236: 2531–2544, 2018) or more predictable (Grover FM, Nalepka P, Silva PL, Lorenz T, Riley MA. Exp Brain Res 237: 687–703, 2019). Under these circumstances, grip force is instead only intermittently coupled to load force; continuous coupling is prompted only when load force levels or variations become sufficiently high or unpredictable. The current study investigated the nature of the transition between continuous and intermittent modes of grip force control by scaling the load force level and the oscillation amplitude continuously in time by means of scaling the required frequency of movement oscillations. Participants grasped a cylindrical object between the thumb and forefinger and oscillated their arm about the shoulder in the sagittal plane. Oscillation frequencies were paced with a metronome that scaled through an ascending or descending frequency progression. Due to greater accelerations, faster frequencies produced greater overall load force levels and more pronounced load oscillations. We observed smooth but nonlinear transitions between clear regimes of intermittent and continuous grip force-load force coordination, for both scaling directions, indicating that grip force control can flexibly reorganize as parameters affecting grasp (e.g., variations in load force) change over time. NEW & NOTEWORTHY Grip force (GF) is synchronously coupled to changing load forces (LF) during object manipulation when LF levels are high or unpredictable, but only intermittently coupled to LF during less challenging grasp conditions. This study characterized the nature of transitions between synchronous and intermittent GF-LF coupling, revealing a smooth but nonlinear change in intermittent GF modulation in response to continuous scaling of LF amplitude. Intermittent, “drift-and-act” control may provide an alternative framework for understanding GF-LF coupling.

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

Do novel gravitational environments alter the grip-force/load-force coupling at the fingertips?

2005 ◽  
Vol 163 (3) ◽  
pp. 324-334 ◽  
Author(s):  
Olivier White ◽  
Joseph McIntyre ◽  
Anne-Sophie Augurelle ◽  
Jean-Louis Thonnard
Keyword(s):  
Grip Force ◽  
Load Force ◽  
Force Load ◽  
Force Coupling

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).

Force level independent representations of predictive grip force–load force coupling: A PET activation study

NeuroImage ◽  
2005 ◽  
Vol 25 (1) ◽  
pp. 243-252 ◽  
Author(s):  
H. Boecker ◽  
A. Lee ◽  
M. Mühlau ◽  
A. Ceballos-Baumann ◽  
A. Ritzl ◽  
...  
Keyword(s):  
Grip Force ◽  
Load Force ◽  
Force Level ◽  
Force Load ◽  
Force Coupling

Grip Force-Load Force Coupling Is Influenced by Altered Visual Feedback about Object Kinematics

2019 ◽  
Vol 52 (5) ◽  
pp. 612-624 ◽  
Author(s):  
Francis M. Grover ◽  
Sarah M. Schwab ◽  
Michael A. Riley
Keyword(s):  
Visual Feedback ◽  
Grip Force ◽  
Load Force ◽  
Force Load ◽  
Force Coupling

scholarly journals Stretching the skin of the fingertip creates a perceptual and motor illusion of touching a harder spring

2017 ◽  
Author(s):  
Mor Farajian ◽  
Raz Leib ◽  
Tomer Zaidenberg ◽  
Ferdinando Mussa-Ivaldi ◽  
Ilana Nisky
Keyword(s):  
Mechanical Properties ◽  
Force Control ◽  
Grip Force ◽  
Tactile Feedback ◽  
Load Force ◽  
Robot Assisted ◽  
Haptic Devices ◽  
Grip Force Control ◽  
Skin Stretch ◽  
Robot Assisted Surgery

AbstractWe investigated how artificial tactile feedback in the form of a skin-stretch affects perception of stiffness and grip force adjustment. During interactions with objects, information from kinesthetic and tactile sensors is used to estimate the forces acting on the limbs. These enable the perception of the mechanical properties of objects to form, and the creation of internal models to predict the consequences of interactions with these objects, such as feedforward grip-force adjustments to prevent slippage. Previous studies showed that an artificial stretch of the skin of the fingertips can produce a linear additive effect on stiffness perception, but it remains unclear how such stretch affects the control of grip force. Here, we used a robotic device and a custom-built skin-stretch device to manipulate kinesthetic and tactile information. Using a stiffness discrimination task, we found that adding artificial tactile feedback to a kinesthetic force can create the illusion of touching a harder spring which affects both perception and action. The magnitude of the illusion is linearly related to the amplitude of the applied stretch. We also isolated the contribution of tactile stimulation to the predictive and reactive components of grip force adjustment, and found that unlike in other cases of perceptual illusions, the predictive grip force is modulated consistently with the perceptual tactile-induced illusion. These results have major implications for the design of tactile interfaces across a variety of touch applications such as wearable haptic devices, teleoperations, robot-assisted surgery, and prosthetics.Significance StatementSensing forces, using kinesthetic and tactile modalities, is important for assessing the mechanical properties of objects, and for acting the objects while stabilizing grasp against slippage. A major challenge in understanding the internal representations that allow for a predictive grip force control during contact with objects is to dissociate the contribution of tactile and kinesthetic stimuli. To date, this contribution was investigated only in impaired cases either through local anesthesia or in patients with sensory impairment. Our study demonstrates using a programmable mechatronic device that artificially applied skin-stretch creates an illusion of a greater load force that affects grip force control and stiffness perception. These results are applicable in tactile technologies for wearable haptic devices, teleoperation, robot-assisted surgery, and prosthetics.

scholarly journals The Effect of Between-Probe Variability in Haptic Feedback on Stiffness Perception and Grip Force Adjustment

2020 ◽  
Author(s):  
Hanna Kossowsky ◽  
Mor Farajian ◽  
Amit Milstein ◽  
Ilana Nisky
Keyword(s):  
Force Field ◽  
Force Control ◽  
Grip Force ◽  
Haptic Feedback ◽  
Weighted Average ◽  
Load Force ◽  
Haptic Information ◽  
Grip Force Control ◽  
Medium Level ◽  
Variability Level

AbstractWhen interacting with objects, haptic information is used to create perception of the object stiffness and to regulate grip force. Studies have shown that introducing noise into sensory inputs can create uncertainty in those sensory channels, yet a method of creating haptic uncertainty without distorting the haptic information has yet to be discovered. Toward this end, we investigated the effect of between-probe haptic variability on stiffness perception and grip force control. In a stiffness discrimination task, we added different levels of between-probe haptic variability by changing the stiffness of the force fields between consecutive probes. Unlike the low and high variability levels, the medium level created perceptual haptic uncertainty. Additionally, we ascertained that participants calculated a weighted average of the different stiffness levels applied by a given force field. Examining participants’ grip force showed that the modulation of the grip force with the load force decreased with repeated exposure to the force field, whereas no change in the baseline was observed. These results were observed in all the variability levels and suggest that between-probe variability created haptic uncertainty that affected the grip force control. Overall, the medium variability level can be effective in inducing uncertainty in both perception and action.

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.

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