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Julie Grèzes

Possible papers associated with this exact author name in Arrow. This page groups case-insensitive exact name matches and is not a full identity disambiguation profile.

6 papers

1 author row

YNIMG Journal 2023 Journal Article

Whose emotion is it? Perspective matters to understand brain-body interactions in emotions

Tahnée Engelen
Anne Buot
Julie Grèzes
Catherine Tallon-Baudry

Feeling happy, or judging whether someone else is feeling happy are two distinct facets of emotions that nevertheless rely on similar physiological and neural activity. Differentiating between these two states, also called Self/Other distinction, is an essential aspect of empathy, but how exactly is it implemented? In non-emotional cognition, the transient neural response evoked at each heartbeat, or heartbeat evoked response (HER), indexes the self and signals Self/Other distinction. Here, using electroencephalography (n = 32), we probe whether HERs' role in Self/Other distinction extends also to emotion - a domain where brain-body interactions are particularly relevant. We asked participants to rate independently validated affective scenes, reporting either their own emotion (Self) or the emotion expressed by people in the scene (Other). During the visual cue indicating to adopt the Self or Other perspective, before the affective scene, HERs distinguished between the two conditions, in visual cortices as well as in the right frontal operculum. Physiological reactivity (facial electromyogram, skin conductance, heart rate) during affective scene co-varied as expected with valence and arousal ratings, but also with the Self- or Other- perspective adopted. Finally, HERs contributed to the subjective experience of valence in the Self condition, in addition to and independently from physiological reactivity. We thus show that HERs represent a trans-domain marker of Self/Other distinction, here specifically contributing to experienced valence. We propose that HERs represent a form of evidence related to the 'I' part of the judgement 'To which extent do I feel happy'. The 'I' related evidence would be combined with the affective evidence collected during affective scene presentation, accounting at least partly for the difference between feeling an emotion and identifying it in someone else.

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YNIMG Journal 2020 Journal Article

Rapid approach-avoidance responses to emotional displays reflect value-based decisions: Neural evidence from an EEG study

Rocco Mennella
Emma Vilarem
Julie Grèzes

The ability to swiftly and accurately respond to others' non-verbal signals, such as their emotional expressions, constitutes one of the building blocks for social adaptation. It is debated whether rapid action tendencies to socio-emotional signals solely depend upon stimulus-evoked pre-decisional motor bias or can also engage goal-directed (decisional) processes that involve the arbitration between action alternatives. Here, we used drift diffusion models (DDMs) of choice and electroencephalography (EEG) to investigate the impact of threat-signaling individuals (angry or fearful) on spontaneous approach-avoidance decisions. Participants choose to avoid angry individuals more often than fearful ones and this effect was stronger for intense expressions. Diffusion models showed that this pattern of choice was accounted for by a process of value-based evidence accumulation, suggesting an active competition between action options. At the brain level, we found that EEG activity preceding movement initiation (200 ms) in a mid-frontal cluster of electrodes – sourced in the orbital and ventromedial frontal cortices – encoded value difference between chosen and unchosen options, thus predicting participant's choices on a trial-by-trial basis. Furthermore, value difference also modulated EEG signal during feedback about the decision. Altogether, the present findings convincingly support the underestimated influence of implicit goal-directed mechanisms in approach-avoidance responses to socio-emotional signals.

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YNICL Journal 2016 Journal Article

Classification of autistic individuals and controls using cross-task characterization of fMRI activity

Guillaume Chanel
Swann Pichon
Laurence Conty
Sylvie Berthoz
Coralie Chevallier
Julie Grèzes

Multivariate pattern analysis (MVPA) has been applied successfully to task-based and resting-based fMRI recordings to investigate which neural markers distinguish individuals with autistic spectrum disorders (ASD) from controls. While most studies have focused on brain connectivity during resting state episodes and regions of interest approaches (ROI), a wealth of task-based fMRI datasets have been acquired in these populations in the last decade. This calls for techniques that can leverage information not only from a single dataset, but from several existing datasets that might share some common features and biomarkers. We propose a fully data-driven (voxel-based) approach that we apply to two different fMRI experiments with social stimuli (faces and bodies). The method, based on Support Vector Machines (SVMs) and Recursive Feature Elimination (RFE), is first trained for each experiment independently and each output is then combined to obtain a final classification output. Second, this RFE output is used to determine which voxels are most often selected for classification to generate maps of significant discriminative activity. Finally, to further explore the clinical validity of the approach, we correlate phenotypic information with obtained classifier scores. The results reveal good classification accuracy (range between 69% and 92.3%). Moreover, we were able to identify discriminative activity patterns pertaining to the social brain without relying on a priori ROI definitions. Finally, social motivation was the only dimension which correlated with classifier scores, suggesting that it is the main dimension captured by the classifiers. Altogether, we believe that the present RFE method proves to be efficient and may help identifying relevant biomarkers by taking advantage of acquired task-based fMRI datasets in psychiatric populations.

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YNIMG Journal 2015 Journal Article

Selective attention effects on early integration of social signals: Same timing, modulated neural sources

Marwa El Zein
Lucile Gamond
Laurence Conty
Julie Grèzes

Humans combine co-emitted social signals to predict other's immediate intentions and prepare an adapted response. However, little is known about whether attending to only one of co-emitted social signals impacts on its combination with other signals. Here, using electroencephalography, we address selective attention effects on early combination of social signals. We manipulated three visual cues: gaze direction, emotional expression, and pointing gesture, while participants performed either emotion or gaze direction judgments. Results showed that a temporal marker of social cues integration emerges 170ms after the stimulus onset, even if the integration of the three visual cues was not required to perform the task, as only one feature at a time was task relevant. Yet in addition to common temporal regions, the relative contribution of specific neural sources of this integration changed as a function of the attended feature: integration during emotion judgments was mainly implemented in classic limbic areas but in the dorsal pathway during gaze direction judgments. Together, these findings demonstrate that co-emitted social cues are integrated as long as they are relevant to the observer, even when they are irrelevant to the ongoing task.

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YNIMG Journal 2009 Journal Article

Two different faces of threat. Comparing the neural systems for recognizing fear and anger in dynamic body expressions

Swann Pichon
Beatrice de Gelder
Julie Grèzes

Being exposed to fear or anger signals makes us feel threatened and prompts us to prepare an adaptive response. Yet, while fear and anger behaviors are both threat signals, what counts as an adaptive response is often quite different. In contrast with fear, anger is often displayed with the aim of altering the behavior of the agent to which it is addressed. To identify brain responses that are common or specific to the perception of these two types of threat signals, we used functional magnetic resonance imaging and asked subjects to recognize dynamic actions expressing fear, anger and neutral behaviors. As compared with neutral actions, the perception of fear and anger behaviors elicited comparable activity increases in the left amygdala and temporal cortices as well as in the ventrolateral and the dorsomedial prefrontal cortex. Whereas the perception of fear elicited specific activity in the right temporoparietal junction, the perception of anger triggered condition-specific activity in a wider set of regions comprising the anterior temporal lobe, the premotor cortex and the ventromedial prefrontal cortex, consistent with the hypothesis that coping with threat from exposure to anger requires additional contextual information and behavioral adjustments.

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YNIMG Journal 2001 Journal Article

Does Perception of Biological Motion Rely on Specific Brain Regions?

Julie Grèzes
Pierre Fonlupt
Bennett Bertenthal
Chantal Delon-Martin
Christoph Segebarth
Jean Decety

Perceptionof biological motions plays a major adaptive role in identifying, interpreting, and predicting the actions of others. It may therefore be hypothesized that the perception of biological motions is subserved by a specific neural network. Here we used fMRI to verify this hypothesis. In a group of 10 healthy volunteers, we explored the hemodynamic responses to seven types of visual motion displays: drifting random dots, random dot cube, random dot cube with masking elements, upright point-light walker, inverted point-light walker, upright point-light walker display with masking elements, and inverted point-light walker display with masking elements. A gradient in activation was observed in the occipitotemporal junction. The responses to rigid motion were localized posteriorly to those responses elicited by nonrigid motions. Our results demonstrate that in addition to the posterior portion of superior temporal sulcus, the left intraparietal cortex is involved in the perception of nonrigid biological motions.

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