Reach-to-grasp movements feature the integration of a reach directed by the extrinsic (location) features of a target and a grasp directed by the intrinsic (size, shape) features of a target. The action-perception theory suggests that integration and scaling of a reach-to-grasp movement, including its trajectory and the concurrent digit shaping, are features that depend upon online action pathways of the dorsal visuomotor stream. Scaling is much less accurate for a pantomime reach-to-grasp movement, a pretend reach with the target object absent. Thus, the action-perception theory proposes that pantomime movement is mediated by perceptual pathways of the ventral visuomotor stream. A distinguishing visual feature of a real reach-to-grasp movement is gaze anchoring, in which a participant visually fixates the target throughout the reach and disengages, often by blinking or looking away/averting the head, at about the time that the target is grasped. The present study examined whether gaze anchoring is associated with pantomime reaching. The eye and hand movements of participants were recorded as they reached for a ball of one of three sizes, located on a pedestal at arms’ length, or pantomimed the same reach with the ball and pedestal absent. The kinematic measures for real reach-to-grasp movements were coupled to the location and size of the target, whereas the kinematic measures for pantomime reach-to-grasp, although grossly reflecting target features, were significantly altered. Gaze anchoring was also tightly coupled to the target for real reach-to-grasp movements, but there was no systematic focus for gaze, either in relation with the virtual target, the previous location of the target, or the participant’s reaching hand, for pantomime reach-to-grasp. The presence of gaze anchoring during real vs. its absence in pantomime reach-to-grasp supports the action–perception theory that real, but not pantomime, reaches are online visuomotor actions and is discussed in relation with the neural control of real and pantomime reach-to-grasp movements.
This is a preview of subscription content, log in to check access.
This work was supported by the Natural Sciences and Engineering Research Council of Canada (NSERC) [JRK], NSERC Discovery Grant [JBD], and NSERC Discovery Grant [JMK]. The authors would like to thank Tsz Yin (Ian) Fung for his help with data collection.
Compliance with ethical standards
Conflict of interest
The authors declare no competing financial interests.
Arbib MA (1981). Perceptual structures and distributed motor control. Comprehensive physiologyGoogle Scholar
de Bruin N, Sacrey L-AR, Brown LA, Doan J, Whishaw IQ (2008) Visual guidance for hand advance but not hand withdrawal in a reach-to-eat task in adult humans: reaching is a composite movement. J Motor Behav 40(4):337–346CrossRefGoogle Scholar
Westwood DA, Chapman CD, Roy EA (2000). Pantomimed actions may be controlled by the ventral visual stream. Exp Brain Res, 130(4)Google Scholar
Whishaw IQ, Suchowersky O, Davis L, Sarna J, Metz GA, Pellis SM (2002) Impairment of pronation, supination, and body co-ordination in reach-to-grasp tasks in human Parkinson’s disease (PD) reveals homology to deficits in animal models. Behav Brain Res 133(2):165–176CrossRefPubMedGoogle Scholar