Neural Representations of Sensorimotor Memory- and Digit Position-Based Load Force Adjustments Before the Onset of Dexterous Object Manipulation

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.

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Does slippage influence the EEG response to load force variations during object manipulation?

IFMBE Proceedings - 4th European Conference of the International Federation for Medical and Biological Engineering ◽

10.1007/978-3-540-89208-3_500 ◽

2009 ◽

pp. 2097-2100

Author(s):

T. André ◽

J. Delbeke ◽

P. Lefèvre ◽

Jean-Louis Thonnard

Keyword(s):

Object Manipulation ◽

Load Force

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Dexterous Object Manipulation Requires Context-Dependent Sensorimotor Cortical Interactions in Humans

Cerebral Cortex ◽

10.1093/cercor/bhz296 ◽

2019 ◽

Vol 30 (5) ◽

pp. 3087-3101 ◽

Cited By ~ 3

Author(s):

Pranav J Parikh ◽

Justin M Fine ◽

Marco Santello

Keyword(s):

Motor Cortex ◽

Primary Motor Cortex ◽

Object Manipulation ◽

Storage And Retrieval ◽

Relative Contribution ◽

Contact Points ◽

Behavioral Studies ◽

Online Feedback ◽

Digit Position

Abstract Dexterous object manipulation is a hallmark of human evolution and a critical skill for everyday activities. A previous work has used a grasping context that predominantly elicits memory-based control of digit forces by constraining where the object should be grasped. For this “constrained” grasping context, the primary motor cortex (M1) is involved in storage and retrieval of digit forces used in previous manipulations. In contrast, when choice of digit contact points is allowed (“unconstrained” grasping), behavioral studies revealed that forces are adjusted, on a trial-to-trial basis, as a function of digit position. This suggests a role of online feedback of digit position for force control. However, despite the ubiquitous nature of unconstrained hand–object interactions in activities of daily living, the underlying neural mechanisms are unknown. Using noninvasive brain stimulation, we found the role of primary motor cortex (M1) and somatosensory cortex (S1) to be sensitive to grasping context. In constrained grasping, M1 but not S1 is involved in storing and retrieving learned digit forces and position. In contrast, in unconstrained grasping, M1 and S1 are involved in modulating digit forces to position. Our findings suggest that the relative contribution of memory and online feedback modulates sensorimotor cortical interactions for dexterous manipulation.

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Hand Interactions in Rapid Grip Force Adjustments Are Independent of Object Dynamics

Journal of Neurophysiology ◽

10.1152/jn.90593.2008 ◽

2008 ◽

Vol 100 (5) ◽

pp. 2738-2745 ◽

Cited By ~ 20

Author(s):

Olivier White ◽

Noreen Dowling ◽

R. Martyn Bracewell ◽

Jörn Diedrichsen

Keyword(s):

Grip Force ◽

Object Manipulation ◽

Load Force ◽

Single Object ◽

Stereo Display ◽

Force Increase ◽

Robotic Devices ◽

The Moment ◽

Pure Measurement ◽

Object Dynamics

Object manipulation requires rapid increase in grip force to prevent slippage when the load force of the object suddenly increases. Previous experiments have shown that grip force reactions interact between the hands when holding a single object. Here we test whether this interaction is modulated by the object dynamics experienced before the perturbation of the load force. We hypothesized that coupling of grip forces should be stronger when holding a single object than when holding separate objects. We measured the grip force reactions elicited by unpredictable load perturbations when participants were instructed to hold one single or two separate objects. We simulated these objects both visually and dynamically using a virtual environment consisting of two robotic devices and a calibrated stereo display. In contrast to previous studies, the load forces arising from a single object could be uncoupled at the moment of perturbation, allowing for a pure measurement of grip force coupling. Participants increased grip forces rapidly (onset ∼70 ms) in response to perturbations. Grip force increases were stronger when the load force on the other hand also increased. No such coupling was present in the reaction of the arms to the load force increase. Surprisingly, however, the grip force interaction did not depend on the nature of the manipulated object. These results show fast obligatory coupling of bimanual grip force responses. Although this coupling may play a functional role for providing stability in bimanual object manipulation, it seems to constitute a relatively hard-wired modulation of a reflex.

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Grip force anticipation of nonlinear, underactuated load force

Journal of Neurophysiology ◽

10.1152/jn.00616.2020 ◽

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.

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Proximal arm kinematics affect grip force-load force coordination

Journal of Neurophysiology ◽

10.1152/jn.00227.2015 ◽

2015 ◽

Vol 114 (4) ◽

pp. 2265-2277 ◽

Cited By ~ 1

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).

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Material evidence: interaction of well-learned priors and sensorimotor memory when lifting objects

Journal of Neurophysiology ◽

10.1152/jn.00263.2012 ◽

2012 ◽

Vol 108 (5) ◽

pp. 1262-1269 ◽

Cited By ~ 40

Author(s):

Lee A. Baugh ◽

Michelle Kao ◽

Roland S. Johansson ◽

J. Randall Flanagan

Keyword(s):

Rate Of Change ◽

Core Material ◽

Load Force ◽

Small Object ◽

Surface Material ◽

Phase Duration ◽

Material Density ◽

Small Cube ◽

Object Weight ◽

Sensorimotor Memory

Skilled object lifting requires the prediction of object weight. When lifting new objects, such prediction is based on well-learned size-weight and material-density correlations, or priors. However, if the prediction is erroneous, people quickly learn the weight of the particular object and can use this knowledge, referred to as sensorimotor memory, when lifting the object again. In the present study, we explored how sensorimotor memory, gained when lifting a given object, interacts with well-learned material-density priors when predicting the weight of a larger but otherwise similar-looking object. Different groups of participants 1st lifted 1 of 4 small objects 10 times. These included a pair of wood-filled objects and a pair of brass-filled objects where 1 of each pair was covered in a wood veneer and the other was covered in a brass veneer. All groups then lifted a larger, brass-filled object with the same covering as the small object they had lifted. For each lift, we determined the initial peak rate of change of vertical load-force rate and the load-phase duration, which provide estimates of predicted object weight. Analysis of the 10th lift of the small cube revealed no effects of surface material, indicating participants learned the appropriate forces required to lift the small cube regardless of object appearance. However, both surface material and core material of the small cube affected the 1st lift of the large block. We conclude that sensorimotor memory related to object density can contribute to weight prediction when lifting novel objects but also that long-term priors related to material properties can influence the prediction.

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Sensorimotor Memory for Object Weight is Based on Previous Experience During Lifting, Not Holding

10.1101/464693 ◽

2018 ◽

Author(s):

Vonne van Polanen ◽

Marco Davare

Keyword(s):

Motor Command ◽

Object Manipulation ◽

Recent Experience ◽

List Type ◽

Holding Period ◽

Object Weight ◽

Object Lifting ◽

Time Period ◽

Sensorimotor Memory ◽

Force Planning

ABSTRACTTo allow skilled object manipulation, the brain must generate a motor command specifically tailored to the object properties. For instance, in object lifting, the forces applied by the fingertips must be scaled to the object’s weight. When lifting a series of objects, forces are usually scaled according to recent experience from previously lifted objects, an effect often referred to as sensorimotor memory. In this study, we investigated the specific time period during which stored information from previous object manipulation is used to mediate sensorimotor memory. More specifically, we examined whether sensorimotor memory was based on weight information obtained between object contact and lift completion (lifting phase) or during stable holding (holding phase). Participants lifted objects in virtual reality that could increase or decrease in weight after the object was lifted and held in the air. In this way, we could distinguish whether the force planning in the next lift was scaled depending on weight information gathered from either the dynamic lifting or static holding period. We found that force planning was based on the previous object weight experienced during the lifting, but not holding, phase. This suggest that the lifting phase, while merely lasting a few hundred milliseconds, is a key time period for building up internal object representations used for planning future hand-object interactions.HIGHLIGHTSWhen lifting objects, fingertip force scaling is based on the most recent liftWe investigated what time period is critical for acquiring sensorimotor memorySensorimotor memory is based on weight experienced during previous lift, not holdThe lifting phase is a key period for building up internal models of object lifting

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