Movement-specific repetition suppression in ventral and dorsal premotor cortex during action observation

There are several models of premotor cortex contributions to sensorimotor behavior. For instance, the ventral premotor cortex (PMv) appears to be involved in processing visuospatial object properties for grasping, whereas the dorsal premotor cortex (PMd) is involved in using arbitrary rules to guide advance motor planning. These models have focused on individual movements. Here, we examine the premotor responses evoked during the processing of individual movements functionally embedded in an action. We tested whether processing hand-object interactions and action end states would differentially engage PMv and PMd. We used a repetition suppression (RS)-functional magnetic resonance imaging paradigm in which we independently manipulated the observed grip, the end position of the object (independent of its spatial location), and the hand trajectory. By comparing novel and repeated trials for each of these action components, we could isolate RS effects specific to each of them. Repeating the grasp component attenuated activity in right PMv, whereas repeating the end state of the action reduced blood oxygen level-dependent activity in the left PMd. These results suggest that PMv is involved in controlling the kinematic means of an appropriate hand-object interaction, whereas PMd is focused on specifying the desired end state of an action.