Is amygdala involved in early gaze processing? An electroencephalography study in epileptic patients with unilateral amygdala resection

Abstract

Event Abstract Back to Event Is amygdala involved in early gaze processing? An electroencephalography study in epileptic patients with unilateral amygdala resection Laurence Conty1, 2*, M. Russo1, D. Dellacherie3, 4, S. Dupont4, M. Denos4, S. Samson3, 4 and N. George1, 2 1 CNRS-UPR640 LENA, France 2 Université Pierre et Marie Curie, Paris 6, France 3 Neuropsychologie et Cognition Auditive-JE 2497, Université Lille-Nord, France 4 Unité d’Epilepsie, Hôpital de la Pitié Salpêtrière, France Detecting the gaze direction of others is fundamental to adaptive interindividual behaviours. In particular, gaze contact appears as a crucial cue to reciprocal social attention and constitutes a frequent preliminary to interaction. In line with this view, several behavioural studies have shown that we are biased at detecting direct gaze as compared to other gaze directions [1]. Moreover, a growing number of studies show that the amygdala is involved in gaze processing, and particularly in processing gaze orientation [2]. This structure has also greater activity during the perception of direct, as compared to averted gaze [3]. This is congruent with the view that gaze contact is an intrinsically arousing stimulus. However, we do not have any information about the temporal involvement of the amygdala in gaze processing. More specifically, does it intervene at an early processing stage? Recently, our group examined the evoked potentials in human adults in response to the apparent motion of gaze [4]. The results showed that the subjects were faster to detect gaze moving toward them (direct gaze condition) as compared to gaze moving away from them (averted gaze condition). Moreover, the perception of direct relative to averted gaze evoked a strong enhancement of the N170 (around 160 ms over occipito-temporal sites), suggesting that gaze contact recruited more resources than averted gaze in the early stage of gaze direction processing. Direct and averted motion of gaze elicited also distinct ERP components between 160 and 210 ms over centro-parietal electrodes. Source reconstruction revealed the involvement of the Theory-of-Mind network, including the regions of the superior temporal sulcus, the medial prefrontal and the orbito-frontal cortices, in these two early dissociations. Nevertheless, the technique of source reconstruction is not ad-hoc to reveal the involvement of sub-cortical structures (such as amygdala). In order to investigate the hypothetic intervention of the amygdala in the early dissociations observed between direct and averted gaze, we used the same protocol by recording epileptic patients with unilateral amygdala resection as well as new control subjects matching with the patients in regard to their age, level of education and socio-professional situation. Currently, 10 patients and 6 control subjects have been processed. Preliminary results revealed that both our behavioural and early electrophysiological results were reproduced in patients and in control subjects. At first view, in epileptic patients, the result were reproduced whatever the side of the resection, in the right (3 subjects) or in the left (8 subjects) hemisphere. These preliminary results strongly suggest that the amygdala does not intervene at the early stage of gaze processing. Moreover, the amygdala does not appear to be necessary for speeding up the detection of direct gaze.