Cerebral Cortex Advance Access originally published online on July 31, 2006
Cerebral Cortex 2007 17(6):1307-1313; doi:10.1093/cercor/bhl041
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Emotion Induction After Direct Intracerebral Stimulations of Human Amygdala
1 Laboratoire Parole et Langage, CNRS et Université de Provence UMR 6054, 13621 Aix-en-Provence, Cedex 1, France, 2 Service de Neurophysiologie Clinique-Unité d'Epileptologie, INSERM U 751 CHU TIMONE et Université de la Méditerranée, 13385 Marseille, Cedex 5, France
Address correspondance to Dr Fabrice Bartolomei MD, PhD, Service de Neurophysiologie Clinique, CHU Timone-264 Rue st Pierre, 13005-Marseille, France. Email: fbartolo{at}medecine.univ-mrs.fr.
Very few studies in humans have quantified the effect obtained after direct electrical stimulation of the amygdala, in terms of both emotional and physiological responses. We tested patients with drug-resistant partial epilepsies who were explored with intracerebral electrodes in the setting of presurgical evaluation. We assessed the effects of direct electric stimulations in either the right or the left amygdala on verbally self-reported emotions (Izard scale) and on psychophysiological markers of emotions by recording skin conductance responses (SCRs) and by measuring the electromyographic responses of the corrugator supercilii (EMGc). According to responses on Izard scales, electrical stimulations of the right amygdala induced negative emotions, especially fear and sadness. In contrast, stimulations of the left amygdala were able to induce either pleasant (happiness) or unpleasant (fear, anxiety, sadness) emotions. Unpleasant states induced by electrical stimulations were accompanied by an increase in EMGc activity. In addition, when emotional changes were reported after electrical stimulation, SCR amplitude for the positively valenced emotions was larger than for the negative ones. These findings provide direct in vivo evidence that the human amygdala is involved in emotional experiences and strengthen the hypothesis of a functional asymmetry of the amygdala for valence and arousal processing.
Key Words: amygdala corrugator supercilii electrodermal emotion fear