Early differences between topographical ERP patterns in response to direct and averted gaze, in the broadband (BB) picture condition.

<p>A) Overview of ERPs in response to direct and averted gaze BB pictures and sample-by-sample t-test of ERP differences between these two conditions. The <i>upper graph</i> represents the overlay of grand mean ERP waveforms obtained on every electrode in response to direct and averted gaze BB pictures. The <i>lower graph</i> represents the number of electrodes for which the p value of the exploratory t-test of ERP differences between direct and averted gaze conditions (performed on each electrode and each time point) reached significance (at an uncorrected threshold of <i>p</i> < .05). The time window delimited by a dashed green rectangle represents the 41–80 ms time window in which different topographical maps were identified for the direct and averted gaze BB picture conditions (see part C of this figure and text). On the right of the graph, a topographical map shows the electrodes that reached the .05 threshold p-value and a bar plot illustrates the early effect showing a scatterplot of the individual participants’ mean amplitude values between 41 and 80 ms for direct and averted gaze at the electrode of maximal t-value (represented by a black dot on topographical map). This showed that the early effect was present in every participant but one. B) Global topographic dissimilarity analysis. The graph represents the statistical level of the global dissimilarity index between the ERP scalp distributions for direct and averted gaze, in the BB picture condition. C) Micro-state segmentation. The five stable topographical maps obtained using the microstate segmentation procedure are represented above the Global Field Power (GFP) for direct and averted gaze BB pictures. The areas under the curves of the GFP are coloured to represent the period of time where each map was stable. Between 41 and 80 ms, distinct maps (maps 1 and 2) were identified for the direct and averted gaze conditions.</p

Example stimulus under each experimental condition of picture filtering (broadband / high spatial frequency / low spatial frequency) and gaze direction (direct / averted).

<p>These avatar faces were created with FaceGen Modeller 3.5 (see [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0166430#pone.0166430.ref045" target="_blank">45</a>] for details).</p

Source localization in the 41–80 ms time window.

<p>A) Result of the node-wise ANOVA performed on source estimation in the 41–80 ms time window. The nodes showing a significant interaction between FREQUENCIES and GAZE (<i>p</i> < .05 over a minimum of 8ms with a cluster size > 32 solution points) are represented in red over left and right lateral views and horizontal sections of the template brain. B) Bar plot of the estimated source activity over the left parietal cluster identified in A, under each condition of picture filtering (Broadband, HSF, LSF) and gaze direction (direct gaze in black, averted gaze in red), showing that the left parietal region was significantly more activated for direct than averted gaze in the broadband face condition.</p

Grand mean reaction time (and standard error of the mean) for each emotion and for each cue-target validity conditions.

<p>The resulting gaze cueing effect (RT difference between invalid and valid trials) is indicated in the rightmost column.</p

Talairach coordinates (in mm) of the vertex showing the maximum difference of source activity for valid versus invalid targets following fearful gaze cues, in the parietal and occipital regions.

<p>Talairach coordinates (in mm) of the vertex showing the maximum difference of source activity for valid versus invalid targets following fearful gaze cues, in the parietal and occipital regions.</p

Example of a fear congruent trial.

<p>Each trial started with the presentation of a fixation cross in the center of the screen for 500 to 800 ms. A neutral face gazing at the participant was then presented for 500 ms. Then, the emotion of the face changed to either a fearful (here) or a happy expression, and the eyes were simultaneously averted either to the right or to the left side of the screen, or remained straight ahead. After a variable SOA of 300 to 450 ms, the target checkerboard appeared either on the right or on the left side of the screen. The subject’s task was to respond to the target as fast as possible. The target and the face stayed on screen until the subject’s response or during 1 s maximum.</p

Result of the additional behavioral experiment.

<p>Using the same material, the same paradigm than the EEG experiment and the same number of participants (N = 15), we asked participants to answer as quickly as possible to the gender of each pictures. Critically, the direct gaze condition with broadband filtering is performed significantly faster than its averted counterpart.</p

Time course of the attention orienting effect induced fearful gaze.

<p>The time course of the grand-averaged ERFs is represented on the five sensors of interest, under the 4 experimental conditions of cue-target validity and emotion.</p

Source localization of the early attention orienting effect induced by fearful gaze cues.

<p>The grand average of the mean source amplitude difference between the valid and the invalid conditions in the 55–70 ms time window are projected on a left lateral view of a template brain. Only sources with a mean amplitude of source activation difference above 3 pA.m are represented. The black dots represent the cortical sources where the cue-target validity effect reached significance (p<.001; 15 vertices in the left superior parietal lobule region and 13 vertices in the left lateral middle occipital gyrus region). The smaller brain on the top illustrates the absence of significant activation in response to valid versus invalid targets in the same time window for happy gaze cues. On the right: Grand mean time course of the vertex showing the maximal source amplitude difference for valid versus invalid targets following fearful gaze cues.</p

Early (55–70 ms) attention orienting effect induced fearful gaze.

<p>a) Grand mean maps of the mean amplitude of ERF in response to targets between 55 and 70 ms, under the four experimental conditions of cue-target validity and emotion. The white dots represent the 5 parietal sensors of measurement. b) Bar plots of the mean amplitude of ERFs on the five sensors of measurement between 55 and 70 ms, for valid, invalid, and catch trials following fearful and happy gaze cues. The bars represent grand mean values, and the lines represent the standard error of the mean.</p