Overview of the workflow.

(A) Planar view of the experimental setup. (B) Schematic diagram of the setup unit. The orthogonal optical data recorded by the motion cameras were sent to the host computer through the Lock unit. The main system used the orthogonal optical data to generate the grasping skeleton template we have created based on the position of the markers on the dorsal surface of the hand: IND (index finger), THU (thumb), WR1 (wrist, left side) and WR2 (wrist, right side). In turn, the position of the index finger and thumb markers was used in real time to activate the vibration motors through the Arduino UNO microcontroller. Arduino UNO was also responsible for triggering the start and stop VICON system capture during the experiment. (C) Characteristics of the devices used in the experiment.</p

Saccade amplitude values during pre- and post-grasping manual estimation phases.

(A) Scatter plots representing post-grasping phase saccades against pre-grasping phase saccades under the different horizontal size perturbation conditions: non-perturbation (black squares), shortening (blue circles) and lengthening (orange rhombuses). Reference diagonal is defined by the dashed line. (B) Difference between saccadic amplitude values inthe post- and pre- grasping phases for each size perturbation condition. Saccadic amplitude values are shown in degrees (deg). Error bars from the bar charts indicate pooled standard deviations. Asterisks indicate p-values less than 0.05.</p

Task design.

(A) Scheme of the experimental paradigm. (B) Tactile feedback implementation during the grasping phase. Tactile feedback was implemented through the coordinates of the index finger and thumb spherical markers. Once these markers were at a distance of ≤1cm from the screen, the vibration was activated. The graphs on the right show two examples illustrating the position of the markers (index finger and thumb) with respect to the screen position and the vibration threshold. Two conditions are exemplified: static position and moving position (grasping).</p

Relationship between grip aperture values and horizontal bar sizes.

(A) Grip aperture values in pre- and post-grasping phases for each horizontal bar size and horizontal perturbation conditions (non-perturbation, shortening, and lengthening). (B) Grip aperture difference values clustered into 2 groups of bar sizes (Cluster-1: sizes 1 to 5; Cluster-2: sizes 6 to 10). Each bar represents the different horizontal size perturbation conditions for each size cluster: non-perturbation (black), shortening (blue) and lengthening (orange). Values from bar charts are represented as pooled mean and error bars as pooled standard deviations. All values are presented in millimetres (mm). Bar sizes from 1 to 10 (in ascending order): 3.18, 3.56, 3.94, 4.32, 4.71, 5.09, 5.47, 5.85, 6.23, 6.62 deg.</p

Grip aperture difference values between pre- and post-grasping phases clustered by 2 groups of bar sizes.

Grip aperture difference values between pre- and post-grasping phases clustered by 2 groups of bar sizes.</p

Multiple regression analysis of the association between bar sizes and predictors (grip aperture and saccade amplitude).

Multiple regression analysis of the association between bar sizes and predictors (grip aperture and saccade amplitude).</p

Grip aperture values during pre- and post-grasping manual estimation phases.

(A) Scatter plot representing post-grasping phase perceptual responses against pre-grasping phase responses under the different horizontal size perturbation conditions: non-perturbation (black squares), shortening (blue circles) and lengthening (orange rhombuses). Reference diagonal is defined by the dashed line. (B) Difference between grip aperture values in the post- and pre- grasping phases for each size perturbation condition. Grip aperture values are shown in millimetres (mm). Error bars from the bar charts indicate pooled standard deviations. Asterisks indicate p-values less than 0.05.</p

Comparison of the effects of fixation depth and gaze laterality on neural activity.

<p>Percentages and number of neurons (in brackets) significantly (ANOVA, P<0.05) influenced by each experimental variable. Gaze laterality is defined as gaze direction in space with respect to the recording hemisphere. Gaze directions at monkey's straight ahead are defined as central.</p

Example of a cell modulated during outward and inward attention epochs.

<p>This cell was excited during outward attention epoch when attention was covertly directed towards bottom locations, and inhibited during inward attention epoch for all attended locations. In addition, this cell was excited during button release and in the visual epoch, especially in the 3 lower positions. Neural activity and eye traces are aligned three times: from left to right: with the cue onset, with the button release and with the change in color of the fixation point. Peri-event time histograms: binwidth, 40 ms; scalebars, 180 spikes/s. Eyetraces: scalebar, 60°. Other details as in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0015078#pone-0015078-g001" target="_blank">Figures 1</a> and <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0015078#pone-0015078-g002" target="_blank">2</a>.</p

Example of a neuron with perisaccadic activity modulated by depth.

<p>(A): Spike histograms of neural responses, eye traces (version upper trace, vergence lower trace) to the five LEDs of the contralateral/central row arranged from near (left) to far (right), aligned at the start of the saccade. This cell shows a clear preference for saccades at the central and near space. (B): Mean± standard error (s.e.m.) discharge rates of the cell in (A) are shown for each LED of the contralateral (white rectangles) and central (black circles) row. (C): Three dimensonal plot obtained by interpolating mean discharge rates for the average value of vergence and version of each LED of the contralateral (white rectangles) and central (black circles) row. Vergence modulates this cell only along the midsagittal row.</p