The role of vision on hand preshaping during reach to grasp

Abstract

During reaching to grasp objects with different shapes hand posture is molded gradually to the object's contours. The present study examined the extent to which the temporal evolution of hand posture depends on continuous visual feedback. We asked subjects to reach and grasp objects with different shapes under five vision conditions (VCs). Subjects wore liquid crystal spectacles that occluded vision at four different latencies from onset of the reach. As a control, full-vision trials (VC5) were interspersed among the blocked vision trials. Object shapes and all VCs were presented to the subjects in random order. Hand posture was measured by 15 sensors embedded in a glove. Linear regression analysis, discriminant analysis, and information theory were used to assess the effect of removing vision on the temporal evolution of hand shape. We found that reach duration increased when vision was occluded early in the reach. This was caused primarily by a slower approach of the hand toward the object near the end of the reach. However, vision condition did not have a significant effect on the covariation patterns of joint rotations, indicating that the gradual evolution of hand posture occurs in a similar fashion regardless of vision. Discriminant analysis further supported this interpretation, as the extent to which hand posture resembled object shape and the rate at which hand posture discrimination occurred throughout the movement were similar across vision conditions. These results extend previous observations on memory-guided reaches by showing that continuous visual feedback of the hand and/or object is not necessary to allow the hand to gradually conform to object contours.

Using Object Affordances to Improve Object Recognition

“…From this point fo view, the dB has the potentiality to support much more research than is described here; in fact, here we have been neglecting the orientation of the hand at the time of grasping, the dynamics embedded in the reaching phase (containing a lot of information more, see, e.g. [34], [35]) and the possibility of exploiting the two points of view (we only use one of the cameras); but these data are available in the dB. Such a research could finally lead to a significant advance also in robotic grasping, too, as the reconstructed grasp might be somehow mapped onto the robotic end-effector in a teloperated setup.…”

To know or not to know: influence of explicit advance knowledge of occlusion on interceptive actions

“…The human perceptuo-motor system has been shown to adapt to information-based perturbations in a variety of tasks, including repetitive (Woodworth 1899;Vince 1948) and discrete aiming tasks (Keele and Posner 1968;Carlton 1981;Moore 1984;Elliott 1988;, grasping (Wing et al 1986;Winges et al 2003;Fukui and Inui 2006), catching (Whiting et al 1970(Whiting et al , 1973Whiting and Sharp 1974;Whiting 1974, 1975;Lamb and Burwitz 1988;Lacquaniti and Maioli 1989;Mazyn et al 2007b;Dessing et al 2009) and hitting (Marinovic et al 2009;van Soest et al 2010). Imposing such perturbations in experimental settings influences factors such as movement preparation, as well as underlying control processes that are responsible for adaptations in kinematics as the movement unfolds (Elliott and Lee 1995;van der Kamp et al 1997;Schenk et al 2004).…”

Egocentric Object Recognition Leveraging the 3D Shape of the Grasping Hand

“…Research in kinesiology and neuroscience reveals that the physical attributes, such as the shape, size and weight, of the object to be grasped by the user determine the posture of the grasping hand, even before contact is made [21,22,29]. These findings largely motivated the research conducted in this paper.…”

“…The shape, size and weight of the object to be grasped determine the posture of the hand even before contact is made [29]. A variety of grips that can be broadly distinguished into precision or power grips and further subdivided into finer categories have been identified in the relevant literature; see [21] and references therein.…”