Fear-Potentiated Startle as a Model System for Analyzing Learning and Memory

摘要

Research during this funding period has focussed on the role of a particularbrain area, the amygdala, in fear conditioning, using increased acoustic startle amplitude in the presence of a stimulus previously paired with shock as a measure of fear in rats. We have found that (a) electrical stimulation of the amygdala increases startle; (b) mechanical or chemical lesions of the amygdala prevent either footshock or stimuli paired with footshock from elevating startle; (c) there is a direct anatomical connection between the central nucleus of the amygdala and a specific point along the acoustic startle pathway; (d) lesions at several levels of this connection between the amygdala and the startle circuit block conditioned and unconditioned fear; (e) local infusion of specific receptor antagonists into the amygdala prevent the development of fear conditioning; and (f) presentation of a conditioned fear stimulus activates early expression genes (c-fos) in the amygdala. The data strongly implicate the amygdala as a critical brain structure for both the acquisition and expression of conditioned and unconditioned fear. Drugs that reduce anxiety in humans may act by interacting with specific receptors in the amygdala.