Efficiency of Grip Force Adjustments for Impulsive Loading during Imposed and Actively Produced Collisions

Abstract

During object manipulation, both predictive feedforward and reactive feedback mechanisms are available to adjust grip force (GF) levels to compensate for the destabilizing effects of load force changes. During collisions, load force increases impulsively (< 20 ms). Thus, only predictive control of GF can be used to ensure grasp stabilization. A collision paradigm is here used to investigate the effects of practice and vision on the efficiency of the predictive control of GF. Subjects actively produced or received an imposed collision with a pendulum. Subjects were more efficient (used smaller GF for identical loads) when producing than when receiving the collisions. Effects of practice were evident in the active producing task only, with GF levels reducing over repetitions, suggesting that sensorimotor memory for the task was used to adjust GF more efficiently. With imposed collisions, GF levels did not reduce with repetition, which suggests that a direct relation between motor action and sensory feedback may be necessary to improve efficiency. Nevertheless, in this condition GF was lower with visual feedback, indicating potential for more efficient grip possibly associated with subjects degree of confidence. We discuss the implications of these results for accounts of the predictive and the reactive control of movement.

Visual impressions of forces between objects: Entraining, enforced disintegration, and shattering

“…For objects of known mass, the planned action is adjusted to take account of the mass of the object in order to ensure that the desired outcome is achieved, and mechanoreceptor feedback is attenuated. However, particularly during learning with unfamiliar objects or objects whose mass or behaviour cannot be assessed prior to action, mass is perceived through the haptic system and action is adjusted if necessary to compensate for this (Delevoye-Turrell, Li, & Wing, 2003;Gandevia & Burke, 1992;Wolpert & Flanagan, 2001).…”

Precision Grip Control while Walking Down a Stair Step

“…This anticipatory mechanism was also studied in collisions induced by a pendulum on a handheld object. A GF increase after the impact was also observed, highlighting the predictive nature of the grip mechanism [8–10]. In addition, the GF/LF adaptation to brisk changes has been studied in altered gravity while performing collisions in a point-to-point task [11–13].…”

Motor Agency: A New and Highly Sensitive Measure to Reveal Agency Disturbances in Early Psychosis

“…To evaluate the motor and agency capacities of the participants, the collision paradigm was used [20]. The subjects' task was to use a hand-held object to resist impacts produced by the collision between the hand-held object and a pendulum (see Figure 1).…”

“…As suggested by the equation, the smaller the safety margin, the more efficient the interaction [20]. The objective indicator of the motor Sense of Agency (SoA) was then taken as the safety margin difference between other-released and self-released collisions [17].…”

“…Indeed, we have proposed the use of the collision paradigm [20] because it requires neither reflective responses nor explicit judgments. It provides the means to reveal behaviourally a difference in experiential states between a situation for which the participant is an active agent of the initiation of a collision, and the contrasting situation for which the same participant is passively experiencing collisions that are initiated by someone else.…”