The role of the amygdala in conditioned and unconditioned fear and anxiety

<jats:title>Abstract</jats:title> <jats:p>Evidence from many different laboratories using a variety of experimental techniques and animal species indicates that the amygdala plays a crucial role in conditioned fear, anxiety, and attention. Many amygdaloid projection areas are critically involved in specific signs used to measure fear and anxiety. Electrical stimulation of the amygdala elicits a pattern of behaviours that mimic natural or conditioned fear. Lesions of the amygdala block innate or conditioned fear, as well as various measures of attention, and local infusion of drugs into the amygdala have anxiolytic or anti-stress effects in several behavioural tests. N-MethylD-aspartate (NMDA) receptors in the amygdala are important in the acquisition of conditioned fear, whereas NMDA or non-NMDA receptors are important for the expression of conditioned fear. The peptide, corticotropin-releasing hormone, appears to be especially important in fear or anxiety and may act within the amygdala, or parts of the extended amygdala, to orchestrate parts of the fear reaction.</jats:p>