Figure 1.

Behavioral task design and recording sites. A, Task paradigm showing the delayed reach-to-grasp task with the epochs fixation, cue, planning, and movement. Monkeys initiated trials by placing both hands on rest sensors and fixating a red LED in the dark. After a delay of 500–700 ms (fixation epoch), target position was revealed together with the instruction (color of a second LED) of which grip type to apply (cue epoch). After a variable delay of 800–1200 ms (planning epoch), a short blink of the fixation light instructed the animal to reach and grasp the target in darkness while maintaining gaze. B, Target could be grasped by performing either a precision grip (left) or a power grip (right). C, Schematic of the reach-to-grasp setup. Having placed both hands on sensors close to the body (open circles), the animal had to grasp a target presented in front of it. Off-center panels mark alternative target and fixation positions. D, Schematic view of spatial variations. Target and gaze position were systematically varied, resulting in the subtasks CV (left) with target and gaze presented in five joint positions, TV (middle) with gaze position in the center, and GV (right) with target position in the center. E, Penetrations sites of recording electrodes (dots) in the cortical areas AIP (along the intraparietal sulcus, IPS) and F5 (along the arcuate sulcus, AS) for both animals. CS indicates central sulcus; PS, principal sulcus. Crosshair in right panel is the chamber coordinate frame.