THE ROLE OF THE AMYGDALA IN EMOTIONAL LEARNING

This chapter reviews the role of the amygdala in emotional learning. The amygdala is an almond-shaped area of the brain lying between the external capsule and the hypothalamus. A brief overview of amygdaloid morphology and electrophysiology is presented. Anatomical targets of the central nucleus of the amygdala that appear important for various signs of fear are enumerated, along with studies looking at the effects of lesions and electrical or chemical stimulation of the amygdala. The chapter shows the possible role of the amygdala in attention as well as the data showing that an intact amygdala is necessary for fear conditioning is mentioned. Finally, the role of excitatory amino acid transmitters in the amygdala in the acquisition and expression of conditioned fear is reviewed. Many of the amygdala projection areas are critically involved in specific signs that are used to measure fear and anxiety. Electrical stimulation of the amygdala elicits a pattern of behaviors that mimics natural or conditioned states of 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 has anxiolytic effects in several behavioral tests. © 1994, Academic Press Inc.