Examples of grasping and reach-only movements.
From A to E: a monkey grasping a cylinder, a cube, a cube placed between two fixed plastic bars and two spheres of different sizes (23 mm and 40 mm). F: a monkey reaching and placing its hand on the disk (reach-only task).

Flatmaps showing grasping-related fMRI activations.
Flatmaps showing grasping-related fMRI responses (p< 0.05, corr.) in contralateral (left) and ipsilateral (right) hemispheres. Black outlines indicate regions of interest. Group data (n = 2). CiS: Cingulate Sulcus. Other conventions as in Figure 3.

Time courses of MR signal in grasping and reaching circuit.
Figure 6A,B: Time courses plotting percent MR signal change for both subjects (M1: A; M2: B) in lateral parieto-frontal grasping circuit (areas AIP and F5p/F5a) over a 2 min period consisting of: 30 seconds each of reach-only (grey), rest, grasping (black), and again rest. Horizontal axis represents time in seconds. Grey bands flanking the time courses indicate variability between epochs.
Figure 6C,D: Time courses plotting percent MR signal change for both subjects (M1: C; M2: D) in the medial parieto-frontal reaching circuit (areas V6A, MIP and F2) as well as in F2vr (distal field of F2), over a 2 min period consisting of: 30 seconds each of reach-only (grey), rest, grasping (black), and rest. Other conventions same as in A and B.
Figure 6E: Raw time course of a single run for AIP and F5p of M1, showing 4 cycles of reach-only - rest - reach-and-grasp - rest. During rest, the monkey kept its gaze upon the central fixation point, while leaving its hand in the start position without moving. Numbers on horizontal axis indicate time in seconds, numbers on y-axis indicate arbitrary scanner units.

Grasping setup and experimental design
Figure 1A: The MR-compatible device for studying grasping consists of a horizontal rotating disk containing 5 different objects. The objects are connected through a plastic shaft to a small plastic weight under the disk, allowing the objects to fall back in place after being grasped and lifted by the monkey. One slot on the disk is left empty for the reach-only trials. The rotating disk is powered by an MR-compatible pneumatic stepper motor and connected through a belt and gear system below the disk. Start and end positions for the hand trajectory during the grasping and reaching trials are indicated. Hand and object position, as well as speed of the transport phase of the hand during the grasping and reaching trials is monitored through the use of several optic switches along the path.
Figure 1B,C: Visual cues used during the grasping and reaching trials. Grasping and reach-only tasks were performed in the dark. In order to initiate the trial, the monkey had to place its right hand in the start position (Figure 1C, arrow1) and fixate a small green fixation point displayed centrally on a screen (Figure 1B). After fixating for a random period of time (500 – 1500 ms) while keeping its hand in the start position, the fixation point changes to blue. This color signals to the monkey that he could reach and, depending on the current task, either grasp and lift (5 mm upwards) the object on the rotating disk (Figure 1C, arrow 2), or place its open hand on the empty slot of the disk (Figure 2F). After holding the object for 530 ms during the grasping trials (or leaving its open hand on the disk for 530 ms during the reach-only trials), a juice reward was given. Failure to either place the hand in the correct start position at the beginning of the trial, failure to grasp and lift the object (or place the hand) within 2000 ms after onset of the blue fixation point, or breaking fixation in general during a trial would result in an abort during which a yellow cross was presented. A new trial (green fixation point) started only if the monkey fixated the fixation point and placed its hand in the correct starting position.

Grasping-related fMRI activations in the monkey brain.
Figure 3A: Top view of template brain (M12) showing cortical areas responding significantly (p< 0.05, corr.) during execution of grasping movements (compared to reach-only). Group data (n = 2). Significant responses were found in ventral premotor cortex F5, primary (area 3a, 3b, 1, 2) and secondary somatosensory cortex, motor area F1, rostral intraparietal sulcus (AIP), rostral inferior (PFG) and superior parietal lobule (area 5).
Figure 3B,C: Lateral views of contralateral (B) and ipsilateral (C) hemispheres showing grasping-related fMRI activations. LuS: Lunate Sulcus, IOS: Inferior Occipital Sulcus, STS: Superior Temporal Sulcus; IPS: Intraparietal Sulcus, CS: Central Sulcus, LS: Lateral Sulcus, AS: Arcuate Sulcus, PS: Principal Sulcus.

Region-of-interest (ROI) analysis.
Figure 5A–F: Plots showing percent MR signal change for both monkey subjects (M1: A, C, E; M2:B, D, F) for reach-only (grey) and grasping (black) compared to rest (fixation-only) for several ROIs in contralateral motor and premotor cortex (A,B), primary and secondary somatosensory cortex (C,D) and parietal cortex (E,F). Asterisks indicate significantly (p< 0.05, corr.) stronger responses for grasping compared to reaching. Errors on the histogram plots indicate variability across runs.