Different roles of PMv and PMd during object lifting.

摘要

The ventral premotor (PMv) and the dorsal premotor (PMd) areas are well placed to influence movements required for object lifting (Fig. 1). In the macaque monkey, these areas connect strongly with the hand area of primary motor cortex and project fibers directly to the spinal cord (DumandStrick, 1991). PMv and the anterior intraparietal cortex transform the representation of the geometrical properties of an object to the motor commands required for grasping (Rizzolatti and Lup-pino, 2001). PMd receives information for the visual guidance of arm movement trajectories required to reach for an object (Rizzolatti et al., 1998) and also selects motor programs based on learned associations (Wise and Murray, 2000; Chouinard and Paus, 2006). Guiding the arm toward an object and the shaping of the hand for grasping are not enough to ensure proper manipulation of objects. To lift objects successfully, people must also apply forces that match their expected weight (Johansson and Westling, 1984).