Effect of blocking tactile information from the fingertips on adaptation and execution of grip forces to friction at the grasping surface

Adaptation of fingertip forces to friction at the grasping surface is necessary to prevent use of inadequate or excessive grip forces. In the current study we investigated the effect of blocking tactile information from the fingertips noninvasively on the adaptation and efficiency of grip forces to surface friction during precision grasp. Ten neurologically intact subjects grasped and lifted an instrumented grip device with 18 different frictional surfaces under three conditions: with bare hands or with a thin layer of plastic (Tegaderm) or an additional layer of foam affixed to the fingertips. The coefficient of friction at the finger-object interface of each surface was obtained for each subject with bare hands and Tegaderm by measuring the slip ratio (grip force/load force) at the moment of slip. We found that the foam layer reduced sensibility for two-point discrimination and pressure sensitivity at the fingertips, but Tegaderm did not. However, Tegaderm reduced static, but not dynamic, tactile discrimination. Adaptation of fingertip grip forces to surface friction measured by the rate of change of peak grip force, and grip force efficiency measured by the grip-load force ratio at lift, showed a proportional relationship with bare hands but were impaired with Tegaderm and foam. Activation of muscles engaged in precision grip also varied with the frictional surface with bare hands but not with Tegaderm and foam. The results suggest that sensitivity for static tactile discrimination is necessary for feedforward and feedback control of grip forces and for adaptive modulation of muscle activity during precision grasp.

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Wrist Action Affects Precision Grip Force

Journal of Neurophysiology ◽

10.1152/jn.1997.78.1.271 ◽

1997 ◽

Vol 78 (1) ◽

pp. 271-280 ◽

Cited By ~ 53

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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Impaired Grip Force Modulation in the Ipsilesional Hand after Unilateral Middle Cerebral Artery Stroke

Neurorehabilitation and Neural Repair ◽

10.1177/1545968305282269 ◽

2005 ◽

Vol 19 (4) ◽

pp. 338-349 ◽

Cited By ~ 52

Author(s):

Barbara M. Quaney ◽

Subashan Perera ◽

Rebecca Maletsky ◽

Carl W. Luchies ◽

Randolph J. Nudo

Keyword(s):

Middle Cerebral Artery ◽

Cerebral Artery ◽

Cognitive Deficits ◽

Grip Force ◽

Precision Grip ◽

Load Force ◽

Cutaneous Sensation ◽

Sensorimotor Processing ◽

Object Weight ◽

Stroke Group

Understanding grasping control after stroke is important for relearning motor skills. The authors examined 10 individuals (5 males; 5 females; ages 32-86) with chronic unilateral middle cerebral artery (MCA) stroke (4 right lesions; 6 left lesions) when lifting a novel test object using skilled precision grip with their ipsilesional (“unaffected”) hand compared to healthy controls (n = 14; 6 males; 8 females; ages 19-86). All subjects possessed normal range of motion, cutaneous sensation, and proprioception in the hand tested and had no apraxia or cognitive deficits. Subjects lifted the object 10 times at each object weight (260 g, 500 g, 780 g) using a moderately paced self-selected lifting speed. The normal horizontal (“grip”) force and vertical tangential (“lift”) force were separately measured at the thumb and index finger. Regardless of the object weight or stroke location, the stroke group generated greater grip forces at liftoff of the object (≥ 39%; P ≤ 0.05) and across the dynamic (P ≤ 0.05) and static portions (P ≤ 0.05) of the lifts compared to the healthy group. Peak lift forces were equivalent between groups, suggesting accurate load force information processing occurred. These results warrant further investigation of altered sensorimotor processing or compensatory biomechanical strategies that may lead to inaccurate grip force execution after strokes.

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Maintaining Grip: Anticipatory and Reactive EEG Responses to Load Perturbations

Journal of Neurophysiology ◽

10.1152/jn.01112.2006 ◽

2008 ◽

Vol 99 (2) ◽

pp. 545-553 ◽

Cited By ~ 16

Author(s):

D. Kourtis ◽

H. F. Kwok ◽

N. Roach ◽

A. M. Wing ◽

P. Praamstra

Keyword(s):

Grip Force ◽

Precision Grip ◽

Reflex Response ◽

Load Force ◽

Brain Potentials ◽

Long Latency ◽

Long Latency Reflex ◽

The Brain ◽

Load Perturbations ◽

Predictable Condition

Previous behavioral work has shown the existence of both anticipatory and reactive grip force responses to predictable load perturbations, but how the brain implements anticipatory control remains unclear. Here we recorded electroencephalographs while participants were subjected to predictable and unpredictable external load perturbations. Participants used precision grip to maintain the position of an object perturbed by load force pulses. The load perturbations were either distributed randomly over an interval 700- to 4,300-ms (unpredictable condition) or they were periodic with interval 2,000 ms (predictable condition). Preparation for the predictable load perturbation was manifested in slow preparatory brain potentials and in electromyographic and force signals recorded concurrently. Preparation modulated the long-latency reflex elicited by load perturbations with a higher amplitude reflex response for unpredictable compared with predictable perturbations. Importantly, this modulation was also reflected in the amplitude of sensorimotor cortex potentials just preceding the long-latency reflex. Together, these results support a transcortical pathway for the long-latency reflex and a central modulation of the reflex grip force response.

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Movement Stability Under Uncertain Internal Models of Dynamics

Journal of Neurophysiology ◽

10.1152/jn.00315.2010 ◽

2010 ◽

Vol 104 (3) ◽

pp. 1301-1313 ◽

Cited By ~ 27

Author(s):

F. Crevecoeur ◽

J. McIntyre ◽

J.-L. Thonnard ◽

P. Lefèvre

Keyword(s):

Grip Force ◽

Precision Grip ◽

Control Policy ◽

Optimization Criterion ◽

Internal Models ◽

Optimal Feedback Control ◽

Load Force ◽

Early Exposure ◽

Short Term Exposure ◽

Movement Stability

Sensory noise and feedback delay are potential sources of instability and variability for the on-line control of movement. It is commonly assumed that predictions based on internal models allow the CNS to anticipate the consequences of motor actions and protect the movements from uncertainty and instability. However, during motor learning and exposure to unknown dynamics, these predictions can be inaccurate. Therefore a distinct strategy is necessary to preserve movement stability. This study tests the hypothesis that in such situations, subjects adapt the speed and accuracy constraints on the movement, yielding a control policy that is less prone to undesirable variability in the outcome. This hypothesis was tested by asking subjects to hold a manipulandum in precision grip and to perform single-joint, discrete arm rotations during short-term exposure to weightlessness (0 g), where the internal models of the limb dynamics must be updated. Measurements of grip force adjustments indicated that the internal predictions were altered during early exposure to the 0 g condition. Indeed, the grip force/load force coupling reflected that the grip force was less finely tuned to the load-force variations at the beginning of the exposure to the novel gravitational condition. During this learning period, movements were slower with asymmetric velocity profiles and target undershooting. This effect was compared with theoretical results obtained in the context of optimal feedback control, where changing the movement objective can be directly tested by adjusting the cost parameters. The effect on the simulated movements quantitatively supported the hypothesis of a change in cost function during early exposure to a novel environment. The modified optimization criterion reduces the trial-to-trial variability in spite of the fact that noise affects the internal prediction. These observations support the idea that the CNS adjusts the movement objective to stabilize the movement when internal models are uncertain.

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The effect of force feedback delay on stiffness perception and grip force modulation during tool-mediated interaction with elastic force fields

Journal of Neurophysiology ◽

10.1152/jn.00229.2014 ◽

2015 ◽

Vol 113 (9) ◽

pp. 3076-3089 ◽

Cited By ~ 20

Author(s):

Raz Leib ◽

Amir Karniel ◽

Ilana Nisky

Keyword(s):

Grip Force ◽

Force Feedback ◽

Force Fields ◽

Precision Grip ◽

Internal Representation ◽

Force Sensor ◽

Elastic Force ◽

Load Force ◽

Perceptual Task ◽

Virtual Force

During interaction with objects, we form an internal representation of their mechanical properties. This representation is used for perception and for guiding actions, such as in precision grip, where grip force is modulated with the predicted load forces. In this study, we explored the relationship between grip force adjustment and perception of stiffness during interaction with linear elastic force fields. In a forced-choice paradigm, participants probed pairs of virtual force fields while grasping a force sensor that was attached to a haptic device. For each pair, they were asked which field had higher level of stiffness. In half of the pairs, the force feedback of one of the fields was delayed. Participants underestimated the stiffness of the delayed field relatively to the nondelayed, but their grip force characteristics were similar in both conditions. We analyzed the magnitude of the grip force and the lag between the grip force and the load force in the exploratory probing movements within each trial. Right before answering which force field had higher level of stiffness, both magnitude and lag were similar between delayed and nondelayed force fields. These results suggest that an accurate internal representation of environment stiffness and time delay was used for adjusting the grip force. However, this representation did not help in eliminating the bias in stiffness perception. We argue that during performance of a perceptual task that is based on proprioceptive feedback, separate neural mechanisms are responsible for perception and action-related computations in the brain.

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Stretching the skin immediately enhances perceived stiffness and gradually enhances the predictive control of grip force

eLife ◽

10.7554/elife.52653 ◽

2020 ◽

Vol 9 ◽

Cited By ~ 2

Author(s):

Mor Farajian ◽

Raz Leib ◽

Hanna Kossowsky ◽

Tomer Zaidenberg ◽

Ferdinando A Mussa-Ivaldi ◽

...

Keyword(s):

Predictive Control ◽

Sensory Processing ◽

Grip Force ◽

Perception And Action ◽

Internal Representation ◽

Load Force ◽

Behavioral Study ◽

Tactile Information ◽

Gradual Development ◽

Kinesthetic Information

When manipulating objects, we use kinesthetic and tactile information to form an internal representation of their mechanical properties for cognitive perception and for preventing their slippage using predictive control of grip force. A major challenge in understanding the dissociable contributions of tactile and kinesthetic information to perception and action is the natural coupling between them. Unlike previous studies that addressed this question either by focusing on impaired sensory processing in patients or using local anesthesia, we used a behavioral study with a programmable mechatronic device that stretches the skin of the fingertips to address this issue in the intact sensorimotor system. We found that artificial skin-stretch increases the predictive grip force modulation in anticipation of the load force. Moreover, the stretch causes an immediate illusion of touching a harder object that does not depend on the gradual development of the predictive modulation of grip force.

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Visual and Tactile Information About Object-Curvature Control Fingertip Forces and Grasp Kinematics in Human Dexterous Manipulation

Journal of Neurophysiology ◽

10.1152/jn.2000.84.6.2984 ◽

2000 ◽

Vol 84 (6) ◽

pp. 2984-2997 ◽

Cited By ~ 64

Author(s):

Per Jenmalm ◽

Seth Dahlstedt ◽

Roland S. Johansson

Keyword(s):

Visual Processing ◽

Visual Cues ◽

Grip Force ◽

Center Of Mass ◽

Precision Grip ◽

Sensory Information ◽

Afferent Input ◽

Dependent Manner ◽

Tactile Sensibility ◽

Grasp Stability

Most objects that we manipulate have curved surfaces. We have analyzed how subjects during a prototypical manipulatory task use visual and tactile sensory information for adapting fingertip actions to changes in object curvature. Subjects grasped an elongated object at one end using a precision grip and lifted it while instructed to keep it level. The principal load of the grasp was tangential torque due to the location of the center of mass of the object in relation to the horizontal grip axis joining the centers of the opposing grasp surfaces. The curvature strongly influenced the grip forces required to prevent rotational slips. Likewise the curvature influenced the rotational yield of the grasp that developed under the tangential torque load due to the viscoelastic properties of the fingertip pulps. Subjects scaled the grip forces parametrically with object curvature for grasp stability. Moreover in a curvature-dependent manner, subjects twisted the grasp around the grip axis by a radial flexion of the wrist to keep the desired object orientation despite the rotational yield. To adapt these fingertip actions to object curvature, subjects could use both vision and tactile sensibility integrated with predictive control. During combined blindfolding and digital anesthesia, however, the motor output failed to predict the consequences of the prevailing curvature. Subjects used vision to identify the curvature for efficient feedforward retrieval of grip force requirements before executing the motor commands. Digital anesthesia caused little impairment of grip force control when subjects had vision available, but the adaptation of the twist became delayed. Visual cues about the form of the grasp surface obtained before contact was used to scale the grip force, whereas the scaling of the twist depended on visual cues related to object movement. Thus subjects apparently relied on different visuomotor mechanisms for adaptation of grip force and grasp kinematics. In contrast, blindfolded subjects used tactile cues about the prevailing curvature obtained after contact with the object for feedforward adaptation of both grip force and twist. We conclude that humans use both vision and tactile sensibility for feedforward parametric adaptation of grip forces and grasp kinematics to object curvature. Normal control of the twist action, however, requires digital afferent input, and different visuomotor mechanisms support the control of the grasp twist and the grip force. This differential use of vision may have a bearing to the two-stream model of human visual processing.

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Effects of local and core body temperature on grip force modulation during movement-induced load force fluctuations

European Journal of Applied Physiology ◽

10.1007/s00421-008-0671-4 ◽

2008 ◽

Vol 103 (1) ◽

pp. 59-69 ◽

Cited By ~ 18

Author(s):

Stephen S. Cheung ◽

Luke F. Reynolds ◽

Mark A. B. Macdonald ◽

Constance L. Tweedie ◽

Robin L. Urquhart ◽

...

Keyword(s):

Body Temperature ◽

Grip Force ◽

Core Body Temperature ◽

Load Force ◽

Force Fluctuations ◽

Force Modulation ◽

Core Body

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Biomechanical Models for Radial Distance Determination by the Rat Vibrissal System

Journal of Neurophysiology ◽

10.1152/jn.00707.2006 ◽

2007 ◽

Vol 98 (4) ◽

pp. 2439-2455 ◽

Cited By ~ 97

Author(s):

J. Alexander Birdwell ◽

Joseph H. Solomon ◽

Montakan Thajchayapong ◽

Michael A. Taylor ◽

Matthew Cheely ◽

...

Keyword(s):

Angular Position ◽

Three Dimensional ◽

Radial Distance ◽

Rate Of Change ◽

Dynamic State ◽

Rhythmic Movements ◽

Tactile Information ◽

Biomechanical Models ◽

Object Distance ◽

Dimensional Object

Rats use active, rhythmic movements of their whiskers to acquire tactile information about three-dimensional object features. There are no receptors along the length of the whisker; therefore all tactile information must be mechanically transduced back to receptors at the whisker base. This raises the question: how might the rat determine the radial contact position of an object along the whisker? We developed two complementary biomechanical models that show that the rat could determine radial object distance by monitoring the rate of change of moment (or equivalently, the rate of change of curvature) at the whisker base. The first model is used to explore the effects of taper and inherent whisker curvature on whisker deformation and used to predict the shapes of real rat whiskers during deflections at different radial distances. Predicted shapes closely matched experimental measurements. The second model describes the relationship between radial object distance and the rate of change of moment at the base of a tapered, inherently curved whisker. Together, these models can account for recent recordings showing that some trigeminal ganglion (Vg) neurons encode closer radial distances with increased firing rates. The models also suggest that four and only four physical variables at the whisker base—angular position, angular velocity, moment, and rate of change of moment—are needed to describe the dynamic state of a whisker. We interpret these results in the context of our evolving hypothesis that neural responses in Vg can be represented using a state-encoding scheme that includes combinations of these four variables.

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