The dynamics of cortico-amygdala and autonomic activity over the experimental time course of fear perception.

Human neuroimaging studies implicate the amygdala, medial prefrontal and somatosensory-related cortices as key neural components in the perception of facial fear signals. Yet, their temporal sequence and interaction with autonomic arousal is not known. We used simultaneous functional magnetic resonance imaging (fMRI) and skin conductance response (SCR) recording in 22 healthy subjects to examine central and autonomic responses to repeated fearful expressions. Phasic SCRs followed a U-shape pattern across early, middle and late presentations of fear stimuli. fMRI data revealed a concomitant temporal sequence of preferential somatosensory insula, dorsomedial prefrontal cortex and left amygdala engagement. These findings suggest that sustained cortico-amygdala and autonomic responses may serve to prime the emotional content of fear signals, and differentiate them from initial stimulus novelty.