Early Amygdala Reaction to Fear Spreading in Occipital, Temporal, and Frontal Cortex: A Depth Electrode ERP Study in Human

The amygdala involvement in fear processing has been reported in behavioral, electrophysiological, and functional imaging studies. However, the literature does not provide precise data on the temporal course of facial emotional processing. Intracranial event-related potentials to facial expressions were recorded in epileptic patients implanted with depth electrodes during a presurgical evaluation. Specific potentials to fear beginning 200 ms poststimulus were observed in amygdala, both individually in two patients and in a ten patient population study. These potentials occurred 100 ms earlier than potentials to disgust recorded in insula in a previous study. Potentials to fear were confined in amygdala during a first transient period and then, during a second period of sustained activity, spread to occipito-temporal, anterior temporal, and orbitofrontal cortex in two patients. This study clarifies the temporal course of the involvement of these structures known to be part of a neural network recruited to process emotional information.