The amygdala and individual differences in human fear conditioning

While animal research on fear conditioning suggests crucial involvement of the amygdala, this has not been corroborated in humans when using subtractive neuroimaging methodology. Correlation analyses might be more able to reveal relations between individual differences in conditionability and central neural activity. Hence, we performed a directed search for amygdalar participation in human fear conditioning by correlating central and autonomic nervous activity. [15O]Butanol positron emission tomography evaluated regional cerebral blood flow (rCBF) in six subjects before and after aversive conditioning to visual snake stimuli. Non-specific electrodermal fluctuations (EDA) were recorded simultaneously. A significant positive correlation was obtained between conditioned EDA and conditioned rCBF in the right amygdala (r = 0.75, p < 0.05), supporting involvement of the amygdala in human fear conditioning.