Reach and Gaze Representations in Macaque Parietal and Premotor Grasp Areas

Voluntary movements are frequently composed of several actions that are combined to achieve a specific behavior. For example, prehension involves reaching and grasping actions to transport the hand to a target to grasp or manipulate it. For controlling these actions, separate parietofrontal networks have been described for generating reaching and grasping actions. However, this separation has been challenged recently for the dorsomedial part of this network (area V6A). Here we report that the anterior intraparietal (AIP) and the rostral ventral premotor area (F5) in the macaque, which are both part of the dorsolateral parietofrontal network and causally linked to hand grasping movements, also represent spatial information during the execution of a reach-to-grasp task. In addition to grip type information, gaze and target positions were represented in AIP and F5 and could be readily decoded from single unit activity in these areas. Whereas the fraction of grip type tuned units increased toward movement execution, the number of cells with spatial representations stayed relatively constant throughout the task, although more prominently in AIP than in F5. Furthermore, the recorded target position signals were substantially encoded in retinotopic coordinates. In conclusion, the simultaneous presence of grasp-related and spatial information in AIP and F5 suggests at least a supportive role of these spatial signals for the planning of grasp actions. Whether these spatial signals in AIP and F5 also play a causal role for the planning of reach actions would need to be the subject of further investigations.