Dissociation of gaze anchoring in real and pantomime reach-to-grasp

Abstract

Prehension consists of two temporally integrated components, a reach and a grasp, each mediated by distinct neural networks. Under visual control, the reach transports the hand to the target while the grasp simultaneously shapes the hand for target purchase. When prehension is performed from memory, as occurs in pantomime, the kinematics of the movement are altered. It is posited that real actions are primarily mediated via the dorsal vision-for-action stream and that pantomime actions are mediated via the ventral vision-for-perception stream. The purpose of the present thesis was to examine components of prehension under conditions of altered cues by monitoring gaze-point and hand kinematics. Removal of cues lead to the dissociation of the reach and grasp such that when the extrinsic properties were present and remained unchanged a real reach was performed with a pantomime grasp. Thus, the reach and grasp, have separate flexible mechanisms by which they can be mediated.