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Early Left Parietal Activity Elicited by Direct Gaze: A High-Density EEG Study

View Article: PubMed Central - PubMed

ABSTRACT

Gaze is one of the most important cues for human communication and social interaction. In particular, gaze contact is the most primary form of social contact and it is thought to capture attention. A very early-differentiated brain response to direct versus averted gaze has been hypothesized. Here, we used high-density electroencephalography to test this hypothesis. Topographical analysis allowed us to uncover a very early topographic modulation (40–80 ms) of event-related responses to faces with direct as compared to averted gaze. This modulation was obtained only in the condition where intact broadband faces–as opposed to high-pass or low-pas filtered faces–were presented. Source estimation indicated that this early modulation involved the posterior parietal region, encompassing the left precuneus and inferior parietal lobule. This supports the idea that it reflected an early orienting response to direct versus averted gaze. Accordingly, in a follow-up behavioural experiment, we found faster response times to the direct gaze than to the averted gaze broadband faces. In addition, classical evoked potential analysis showed that the N170 peak amplitude was larger for averted gaze than for direct gaze. Taken together, these results suggest that direct gaze may be detected at a very early processing stage, involving a parallel route to the ventral occipito-temporal route of face perceptual analysis.

No MeSH data available.


Related in: MedlinePlus

Source localization in the 41–80 ms time window.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 (p < .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.
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pone.0166430.g006: Source localization in the 41–80 ms time window.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 (p < .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.

Mentions: In order to identify the candidate regions underpinning the early topographic difference between direct and averted gaze conditions, LAURA distributed source estimations were calculated over the 41–80 ms time period. We submitted the mean source amplitude estimations obtained in this time window to an ANOVA with FREQUENCIES and GAZE as within-subject factors. This revealed a significant interaction between FREQUENCIES and GAZE, with a maximum peak localized in the left posterior parietal lobe region [Talairach, -9,-82, 41], close to the left precuneus and extending into the inferior parietal lobule, F(2,28) = 4.22, p < .025, ηp2 = .23 (Fig 6A). Post-hoc t-test performed on the source points extracted from this region revealed that direct gaze activated this region more strongly (1.42 ± .103 nV/mm3) than averted gaze (1.01 ± .118 nV/mm3) in the BB picture condition, t(14) = 3.75, p < .02. This effect was not significant for the LSF and HSF pictures (Fig 6B).


Early Left Parietal Activity Elicited by Direct Gaze: A High-Density EEG Study
Source localization in the 41–80 ms time window.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 (p < .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.
© Copyright Policy
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC5120811&req=5

pone.0166430.g006: Source localization in the 41–80 ms time window.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 (p < .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.
Mentions: In order to identify the candidate regions underpinning the early topographic difference between direct and averted gaze conditions, LAURA distributed source estimations were calculated over the 41–80 ms time period. We submitted the mean source amplitude estimations obtained in this time window to an ANOVA with FREQUENCIES and GAZE as within-subject factors. This revealed a significant interaction between FREQUENCIES and GAZE, with a maximum peak localized in the left posterior parietal lobe region [Talairach, -9,-82, 41], close to the left precuneus and extending into the inferior parietal lobule, F(2,28) = 4.22, p < .025, ηp2 = .23 (Fig 6A). Post-hoc t-test performed on the source points extracted from this region revealed that direct gaze activated this region more strongly (1.42 ± .103 nV/mm3) than averted gaze (1.01 ± .118 nV/mm3) in the BB picture condition, t(14) = 3.75, p < .02. This effect was not significant for the LSF and HSF pictures (Fig 6B).

View Article: PubMed Central - PubMed

ABSTRACT

Gaze is one of the most important cues for human communication and social interaction. In particular, gaze contact is the most primary form of social contact and it is thought to capture attention. A very early-differentiated brain response to direct versus averted gaze has been hypothesized. Here, we used high-density electroencephalography to test this hypothesis. Topographical analysis allowed us to uncover a very early topographic modulation (40&ndash;80 ms) of event-related responses to faces with direct as compared to averted gaze. This modulation was obtained only in the condition where intact broadband faces&ndash;as opposed to high-pass or low-pas filtered faces&ndash;were presented. Source estimation indicated that this early modulation involved the posterior parietal region, encompassing the left precuneus and inferior parietal lobule. This supports the idea that it reflected an early orienting response to direct versus averted gaze. Accordingly, in a follow-up behavioural experiment, we found faster response times to the direct gaze than to the averted gaze broadband faces. In addition, classical evoked potential analysis showed that the N170 peak amplitude was larger for averted gaze than for direct gaze. Taken together, these results suggest that direct gaze may be detected at a very early processing stage, involving a parallel route to the ventral occipito-temporal route of face perceptual analysis.

No MeSH data available.


Related in: MedlinePlus