The Timing of Natural Prehension Movements

TLDR

The study examines the central programming of multisegmental movements. The authors filmed prehension movements in seven adult participants. Hand transportation to a target shows a fast‑velocity initial phase followed by a low‑velocity final phase, with peak velocity scaling with amplitude while duration remains constant, and finger grip formation begins during transportation, with closure onset tightly linked to the low‑velocity phase; this pattern persists regardless of visual feedback.

Abstract

Prehension movements were studied by film in 7 adult subjects. Transportation of the hand to the target-object location had features very similar to any aiming arm movement, that is, it involved a fast-velocity initial phase and a low-velocity final phase. The peak velocity of the movement was highly correlated with its amplitude, although total movement duration tended to remain invariant when target distance was changed. The low-velocity phase consistently began after about 75 % of movement time had elapsed. This ratio was maintained for different movement amplitudes. Formation of the finger grip occurred during hand transportation. Fingers were first stretched and then began to close in anticipation to contact with the object. The onset of the closure phase was highly correlated to the beginning of the low velocity phase of transportation. This pattern for both transportation and finger grip formation was maintained in conditions whether visual feedback from the moving limb was present or not. Implications of these findings for the central programming of multisegmental movements are discussed.