A Fun Experiment
Since then, in collaboration with Professors Passingham and Frith from University College London (UCL), she has shown that a whole brain network is involved in detecting false expectations and lies, notably including the superior temporal sulcus, the anterior cingulate cortex, and the amygdala. To study this, she developed functional MRI (fMRI) protocols using simple actions, like lifting a box.
"The preparation of the experiment was fun," says Julie Grèzes, laughing. "We filmed actors entering a room, picking up a box, and leaving. We varied the weight of the box and informed the participants about its weight. But we could also lie, telling them, for example, that the box weighed 1 kg when it actually weighed 12. This false expectation translated into a change in the kinematics of the gesture. Then we asked the actors to fake the weight, pretending to lift a very heavy box that was actually light, or vice versa. Again, lying affected their bodily movements." These short videos were then shown to subjects in an MRI scanner, where they had to judge whether the action reflected a false belief or a deception. In both cases, the superior temporal sulcus, cingulate and orbitofrontal cortices, as well as the cerebellum, were activated. But when there was deception, there was additional activation in the rostral anterior cingulate cortex and especially the amygdala, a key region in emotion generation—especially if the observer felt involved, as a potential target of the lie.
Her collaborations with her British colleagues continue, as she was recently hired as a CR1 (research fellow) at Inserm within the Physiology of Perception and Action Laboratory (UMR CNRS-Collège de France) led by Alain Berthoz. Julie Grèzes has broadened her research by joining forces with Béatrice de Gelder in the Netherlands to study the interactions between the systems of action and those involved in emotion processing. Here, too, the experiments are based on fMRI and short films, where actors mime fear. And again, the amygdala is implicated, responsible for emotional contagion. The study shows that perceiving dynamic bodily expressions of fear activates the parietal cortex, the premotor cortex, the temporal sulcus on one hand, and the amygdala on the other. "The amygdala thus modulates the activity of premotor regions, suggesting that perceiving fear in others could prompt a preparatory action response to potential danger in the observer."
New Perspectives on Autism
This link between the amygdala (emotional contagion) and the premotor cortex (motor resonance) is central to Julie Grèzes' current work on autism. This pervasive developmental disorder is particularly characterized by disruptions in social interactions (gaze anomalies, empathy issues), and verbal and non-verbal communication (imitation, pretend play). "Some researchers suggest that autism could be related to a deficit in resonance, meaning that autistic individuals may not be properly equipped to interpret the actions of others. Others, however, see it as a deficit in emotional contagion—a hypothesis proposed in 2000 by Simon Baron-Cohen from Cambridge University. I believe it may actually be a communication problem between these two systems."
In collaboration with Sylvie Berthoz (Department of Adolescent and Young Adult Psychiatry, Institut Mutualiste Montsouris, Paris) and Bruno Wicker (Mediterranean Institute of Cognitive Neuroscience, CNRS, Marseille), she plans to reproduce her experiments on deception and fear contagion with healthy subjects, as well as with high-functioning autistic or Asperger individuals who exhibit severe socio-cognitive deficits. All participants will complete detailed personality questionnaires. "The goal is to test whether the response of the premotor cortex and amygdala correlates with individuals’ social skills. We want to determine if there’s a continuum in social understanding abilities, from Asperger individuals to those with high empathy scores, or if there’s a 'break' in the curve. We’ll also study the functional connectivity between the activated brain regions."
These analyses go beyond fMRI. Several other approaches are added: behavioral, measuring performances and reaction times, and physiological, tracking eye movement, skin conductance, and pupil dilation. "All of this work could be key in better defining different neurocognitive phenotypes linked to social interaction difficulties. It’s important to clearly characterize these phenotypes, especially in such a heterogeneous condition as autism, to provide targeted therapeutic approaches and also conduct genetic studies, like those of Marion Leboyer..."
Time flies when you’re with passionate people! It’s already time for Julie Grèzes to leave. And there she goes, striding through the Latin Quarter under the sun...