Digit Position and Force Synergies During Unconstrained Grasping

2016 ◽  
pp. 29-40 ◽  
Author(s):  
Abdeldjallil Naceri ◽  
Marco Santello ◽  
Alessandro Moscatelli ◽  
Marc O. Ernst
Keyword(s):  
Digit Position

digit position

2000 ◽  
pp. 415-415
Author(s):  
Martin H. Weik
Keyword(s):  
Digit Position

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

2019 ◽  
Vol 30 (5) ◽  
pp. 3087-3101 ◽  
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.

Multi-digit Position and Force Coordination in Three- and Four-Digit Grasping

2014 ◽  
pp. 101-108 ◽  
Author(s):  
Abdeldjallil Naceri ◽  
Alessandro Moscatelli ◽  
Marco Santello ◽  
Marc O. Ernst
Keyword(s):  
Force Coordination ◽  
Digit Position

scholarly journals Role of digit placement control in sensorimotor transformations for dexterous manipulation

2017 ◽  
Vol 118 (5) ◽  
pp. 2935-2943 ◽  
Author(s):  
Daisuke Shibata ◽  
Marco Santello
Keyword(s):  
Force Feedback ◽  
Force Production ◽  
Passive Movement ◽  
Position Estimation ◽  
Accurate Estimation ◽  
Dexterous Manipulation ◽  
Motor Commands ◽  
Sensorimotor Transformations ◽  
Sensorimotor Mechanisms ◽  
Digit Position

Dexterous manipulation relies on the ability to modulate grasp forces to variable digit position. However, the sensorimotor mechanisms underlying such critical ability are not well understood. The present study addressed whether digit force-to-position modulation relies entirely on feedback of digit placement and force, or on the integration of such feedback with motor commands responsible for digit positioning. In two experiments, we asked 25 subjects to estimate the index fingertip position relative to the thumb (perception test) or to grasp and lift an object with an asymmetrical mass distribution while preventing object roll (action test). Both tests were performed after subjects’ digits were placed actively or passively at different distances (active and passive condition, respectively) and without visual feedback. Because motor commands for digit positioning would be integrated with position and force feedback in the active condition, we hypothesized this condition to be characterized by greater accuracy of digit position estimation and digit force-to-position modulation. Surprisingly, discrimination of digit position and force-to-position modulation was statistically indistinguishable in the active and passive conditions. We conclude that voluntary commands for digit positioning are not essential for accurate estimation of finger position or modulation of digit forces to variable digit position. Thus digit force-to-position modulation can be implemented by integrating sensory feedback of digit position and voluntary commands of digit force production following contact. NEW & NOTEWORTHY This study was designed to understand the sensorimotor mechanisms underlying digit force-to-position modulation required for manipulation. Surprisingly, estimation of relative digit position and force-to-position modulation was accurate regardless of whether the digits were passively or actively positioned. Therefore, accurate estimation of digit position does not require an efference copy of active digit positioning, and the hypothesized advantage of active over passive movement on estimation of end-point position appears to be task and effector dependent.

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