Behavioral performance for all conditions of experiment 2 (luminance).

<p>‘Hits’: Percentage of correct detections. ‘FA rate’: Percentage of false alarms (indications of change when no change was present). ‘d′’: Measure of perceptual sensitivity. Log β: Measure of response bias towards either a change or no-change response.</p

Visual hemifield differences in grasping and pointing performance.

<p>Differences in sensitivity between grasping and pointing are prominent when the stimulus is shown in the right visual field, but not when the stimulus appears in the left visual field.</p

Grasping angle preshaping.

<p>Mean orientation of the thumb-index vector, as a function of target bar orientation (45 or −45 deg) and experiment (orientation/luminance) in the grasping condition. The horizontal axis represents the percent movement completed (0–100%), where 0% is movement onset and 100% is the point where the bar on screen is grasped. Error bars represent the standard error (SE).</p

Behavioral performance for all conditions of experiment 1 (orientation).

<p>‘Hits’: Percentage of correct detections. ‘FA rate’: Percentage of false alarms (indications of change when no change was present). ‘d′’: Measure of perceptual sensitivity. Log β: Measure of response bias towards either a change or no-change response.</p

Experimental paradigm.

<p>(A) Stimulus display used in experiment 1 (orientation) and 2 (luminance). A fixation spot was followed by the appearance of a bar that signaled the go-cue for the action to be executed (by instruction) and which could be either rotated slightly (left, experiment 1) or differ in luminance (right, experiment 2) from the subsequent second bar. A brief fixation period (100 ms) was present between the first and second bar presentation. Subjects responded by key-press after execution of the action. (B) Timeline representation of the paradigm. The top plot represents the grand mean average movement (distance to origin) for either grasping (black) or pointing (gray).</p

Effects of training.

<p>Separate analyses were performed on the first (block 1–2) and second half (block 3–4) of the first (orientation change) experiment. Differences in sensitivity due grasping or pointing preparation become apparent only in the second half of the orientation experiment (1).</p

Kinematic data example.

<p>Exemplar data from grasping and pointing from a single subject, for a single bar position. (A) Velocity profile is taken from the wrist position. The first peak in velocity reflects the initial transport to the screen, whereas the second peak is caused by the retraction from the screen after the grasping/pointing action to the rest position. (B) Height profile is extracted from the thumb and index positions. Here, maximum height is reached when the subjects points to/grasps the bar on screen. Differences in thumb-index height in the grasping condition reflect the grasping aperture.</p

ROI activation timecourse.

<p>The average peri-stimulus-time-histograms (PSTHs; BOLD time courses) are shown for several ROIs: the clusters activated for saccades in darkness vs rest in left and right precentral sulcus/premotor cortex (‘lateral and medial FEF’) and the left and right putamen and SEF, and the left and right clusters in the FEF more active for anti as compared to prosaccades (‘antisaccade FEF’). The aforementioned group activation patterns from which the ROIs were taken are depicted in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0029517#pone-0029517-g004" target="_blank">figure 4</a>. PSTHs were averaged over voxels in the ROIs and then participants, and aligned at target stimulus onset. Saccade onset typically follows within 300 ms, therefore PSTHs aligned at saccade onset would have been largely identical. Data for the left hemisphere are given in the left panels and data for the right hemisphere in the right panels. In each panel, average PSTHs are presented for pro and antisaccades (gray squares and black circles) to the left and right (solid and dashed lines with open and solid symbols). The unit on the ordinate is global % signal change. The absolute magnitude of this unit is not directly meaningful and should not be compared over regions, as averaging took place over different numbers of voxel per region and within different brain areas. Absolute BOLD measures are known to vary considerably over regions. Differences between conditions within a region can be compared. Except the bilateral putamen, the right ‘lateral FEF’ and left SEF, peak activation in all ROIs was significantly larger for antisaccades as compared to prosaccades (p<0.05). The left SEF exhibited larger responses for antisaccades at trend level, T(12) = 1.59;p = 0.06. Further tests on single timepoints of interest are presented in the text of the results section.</p

Field of view (FOV).

<p>The field of view used for fMRI acquisition during task performance, indicated as a blue translucent square overlaid on a sagittal slice through the anatomical scan of one of the participants. Care was taken that the striatum, midbrain, FEF and SEF were in the field of view. In between functional runs, the angulation was checked regularly and adjusted if required.</p

Step-wise results of DTI analysis.

<p>The subsequent steps in DTI fiber analysis are outlined in 4 panels. In panel A, the normalized fiber tracts originating from the left and right putamen and caudate nucleus are rendered in blue for one participant together with orthogonal slices from the normalized T1 weighted scan. The manually segmented ROIs for the caudate nucleus and putamen are also rendered in red. Panel B shows a 3D representation of the average probability (over participants) for a voxel to be connected to the caudate nucleus (in red) or putamen (in blue) or both (purple). In yellow the zones activated for antisaccades and in green the zone activated for saccades in darkness are rendered. For each participant, it was then investigated which fibers from the 4 fiber bundles originating in the left and right putamen and caudate nucleus were connected to the most important cortical fMRI activation clusters observed in 4. See panel C for example results from individual participants: fibers connecting the caudate nucleus and SEF are shown in the left rendering, fibers connecting the putamen and antisaccade zone in the FEF in the right rendering, and the lower left rendering shows fibers connecting the areas activated for saccades in darkness (‘lateral and medial FEF’) with the putamen. The manually segmented caudate nucleus and putamen are also shown in yellow and green, respectively. Panels C is presented in order to illustrate the fiber processing steps, and are not necessarily representative. Panel D shows for how many participants (out of 12) regions were connected at all. ‘FEF motor’ refers to zones along the precentral sulcus activated for saccades in darkness (that is, ‘lateral FEF’ and ‘medial FEF’ taken together), ‘FEF anti’ refers to zones activated for antisaccades vs prosaccades. Line thickness also indicates the number of subjects with connections. The diagram is overlayed onto a blurred slice from <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0029517#pone-0029517-g004" target="_blank">figure 4</a>, only to roughly indicate the location.</p