Abstract The goal of the present study was to under- stand which characteristics (movement time or velocity) of target motion are important in the control and coordi- nation of the transport and grasp-preshape components of prehensile movements during an interception task. Subjects were required to reach toward, grasp and lift an object as it entered a target area. Targets approached along a track at four velocities (500, 750, 1000 and 1250 mm/s) which were presented in two conditions. In the distance-controlled condition, targets moving at all velocities traveled the same distance. In the viewing- time-controlled condition, combinations of velocity and starting distances were performed such that the moving target was visible for 1000 ms for all trials. Analyses of kinematic data revealed that when, target distance was controlled, velocity affected all transport-dependent measures; however, when viewing time was controlled, these dependent measures were no longer affected by target velocity. Thus, the use of velocity information was limited in the viewing-time-controlled condition, and subjects used other information, such as target move- ment time, when generating the transport component of the prehensile movement. For the grasp-preshape com- ponent, both peak aperture and peak-aperture velocity in- creased as target velocity increased, regardless of condi- tion, indicating that target velocity was used to control the spatial aspects of aperture formation. However, the timing of peak aperture was affected by target velocity in the distance-controlled condition, but not in the viewing- time-controlled condition. These results provide evi- dence for the autonomous generation of the spatial and temporal aspects of grasp preshape. Thus, an indepen- dence between the transport and grasp-preshape phases was found, whereby the use of target velocity as a source of information for generating the transport component was limited; however, target velocity was an important source of information in the grasp-preshape phase. Key words Target interception · Reaching · Grasping · Human Introduction The task of reaching for and grasping an object requires the coordination of different motor components, such as hand transport and grasp. The transport (reach) compo- nent involves the displacement of the arm, which brings the hand from its initial position to the target. The grasp- preshape component (i.e. control of the distance between the index and thumb, or finger aperture, prior to contact with the object) is involved in selecting and controlling the fingers’ configurations, according to the stimulus size and shape (Arbib 1981). The initiation and termination of the grasp-preshape and transport phases have been reported to be temporally and spatially linked for simple prehensile tasks (Gent- ilucci et al. 1991; Jeannerod 1984; von Hofsten and Ronnqvist 1988; Wallace and Weeks 1988; Wing and Fraser 1983; Wing et al. 1986). This relationship be- tween the transport and grasp phases can, however, be uncoupled when simple prehensile movements are per- turbed (Gentilucci et al. 1992; Paulignan et al. 1990). Thus, while there is evidence that, for simple move- ments, there is a temporal and spatial coupling of the transport and grasp-preshape systems, when prehensile movements are perturbed, the relationship between the two phases can be uncoupled such that the transport and grasp are organized independently. Jeannerod (1981, 1984) hypothesized the existence of distinct visuomotor channels that work independently and are specialized to program only the transport or the grasp-preshape components. The channeling of visual in- put is related to object characteristics, which have been termed either intrinsic (i.e. size, shape) or extrinsic (i.e. distance, orientation) object properties. Extrinsic proper- A.H. Mason · H. Carnahan ( ✉ ) Department of Kinesiology, University of Waterloo, Waterloo, Ontario, N2L 3G1, Canada e-mail: carnahan@healthy.uwaterloo.ca Fax: +1-519-746-6776 Exp Brain Res (1999) 127:83–94 © Springer-Verlag 1999 RESEARCH ARTICLE Andrea H. Mason · Heather Carnahan Target viewing time and velocity effects on prehension Received: 16 March 1998 / Accepted: 2 February 1999