Patterns of Hand Motion during Grasping and the Influence of Sensory Guidance

TLDR

The study aimed to describe temporal synergies of hand movement and assess how sensory cues influence their control. Participants grasped objects under memory‑guided, virtual‑image, and real‑object conditions while arm and 15 hand degrees of freedom were recorded and analyzed with principal component analysis to capture spatiotemporal patterns. Vision did not affect reaching kinematics, while the physical presence of the object influenced motion only after contact; two principal components explained over 75 % of variance, with PC1 showing a finger extension‑to‑flexion pattern and PC2 emerging only in the latter half of the reach, and both components exhibited strong positive correlations among metacarpophalangeal and proximal interphalangeal joint rotations.

Abstract

This study was aimed at describing temporal synergies of hand movement and determining the influence of sensory cues on the control of these synergies. Subjects were asked to reach to and grasp various objects under three experimental conditions: (1) memory-guided movements, in which the object was not in view during the movement; (2) virtual object, in which a virtual image of the object was in view but the object was not physically present; and (3) real object, in which the object was in view and physically present. Motion of the arm and of 15 degrees of freedom of the hand was recorded. A principal components analysis was developed to provide a concise description of the spatiotemporal patterns underlying the motion. Vision of the object during the reaching movement had no influence on the kinematics, and the effect of the physical presence of the object became manifest primarily after the fingers had contacted the object. Two principal components accounted for >75% of the variance. For both components, there was a strong positive correlation in the rotations of metacarpophalangeal and proximal interphalangeal joints of the fingers. The first principal component exhibited a pattern of finger extension reversing to flexion, whereas the second principal component became important only in the second half of the reaching movement.