Experimental Paradigm.

<p>(<b>A</b>) The participant’s head was tilted to enable fixation upon an LED placed on top of the magnet bore, such that the stimuli were viewed in the lower visual field. The right upper arm was restrained in an arm brace to minimize shoulder movements. The participant shown provided written informed consent, as outlined in the PLOS consent form, to publication of his photograph. (<b>B</b>) In grasping trials, participants performed a precision grip with the finger and thumb along the long axis of the object. In reaching trials, they simply touched the object with the knuckles. Although the hand and object are simultaneously visible in the image, this was not the case in the actual experiment. (<b>C</b>) Each trial began with an auditory cue that instructed the participant about the task on the upcoming trial (“Grasp” or “Reach”) after which the object was illuminated for 250 ms. Following an 18- s delay, an auditory cue instructed the participant to either execute the movement (“Go”) or abort any response (“Stop”). Following the brief visual stimulus, the participant remained in complete darkness during the delay and action periods. (<b>D</b>) Functional slice planes differed between two groups of participants. Group A (left) consisted of 11 participants scanned with a slice orientation that covered most of the frontal lobe and the entire parietal lobe. Group B (right) consisted of 9 participants scanned with a slice orientation that covered the parietal and occipital lobes and part of the temporal lobes. For each group, the white box indicates the functional volume common across all subjects within the group (defined in Talairach space) superimposed on midsagittal and parasagittal (through LOC) slices of a representative participant’s anatomical scan.