The Timing of Natural Prehension Movements

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 ration 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.

Prehension is really reaching and grasping

“…The reaching component of prehension is concerned with bringing the hand to the object to be grasped, whereas the grasping component refers to the opening and closing of the hand. This suggested division of labor stems from the seminal studies performed by Marc Jeannerod, about 25 years ago, which, for the Wrst time, reported details of the kinematics of prehensile movements (Jeannerod 1981(Jeannerod , 1984. Countless studies have addressed all kinds of aspects of prehension, taking this division in components as their starting point.…”

“…As mentioned earlier, with his Wrst systematic analysis of the kinematics of prehension, Jeannerod (1981Jeannerod ( , 1984 set the stage for a large number of studies of the control and coordination of reaching and grasping (for reviews, see Castiello 2005;Jeannerod 1988;MacKenzie and Iberall 1994). Jeannerod's proposal that a reaching (or transport) component and a grasping (or manipulation) component make up prehension was based on a number of arguments, such as anatomical arguments that diVerent muscles and Electronic supplementary material The online version of this article (doi:10.1007/s00221-007-0968-2) contains supplementary material, which is available to authorized users.…”

“…Most often, when the coordination of prehension has been addressed, hypotheses regarding the moment of peak hand aperture, the moment that hand opening goes into hand closing, have been put forward (for an overview, see Zaal and Bootsma 2004). For instance, it has been proposed that peak hand aperture would occur at the moment of peak deceleration of the reaching movement (Jeannerod 1984), at a Wxed time (Gentilucci et al 1992) or distance (Rand and Stelmach 2005;Rand et al 2006;Stelmach 1998, 2001) before hand-object contact, or that coordination is based on time-to-contact information (Bootsma and Van Wieringen 1992;Zaal and Bootsma 2004;Zaal et al 1998). In our opinion, the latter hypothesis is the most promising of the ones currently available, but it certainly still needs a critical test.…”

Non-obstructing 3D depth cues influence reach-to-grasp kinematics

“…Under normal viewing conditions with visual feedback, maximum grip aperture (MGA) typically occurs ~75% relative to the total movement time (Glover, 2002). Numerous other studies have confirmed Jeannerod's (1984) division of prehension into two distinct and separable components (Dohl, Ostermann, Hefter & Freund, 2000;Shallice, Venable & Rumiati, 2005) with some authors demonstrating that these, furthermore, have distinct neural substrates (e.g. Cavina-Pratesi et al 2010).…”

“…During the 1980s, Jeannerod (1981Jeannerod ( , 1984 demonstrated that manual prehension can be divided into two distinct neural and behavioural components -reaching and grasping.…”