The Emotional Brain, Fear, and the Amygdala

The Emotional Brain, Fear, and the Amygdala

SUMMARY

1. Considerable progress has beenmadeover the past 20 years in relating specific circuits

of the brain to emotional functions. Much of this work has involved studies of Pavlovian

or classical fear conditioning, a behavioral procedure that is used to couple meaningless

environmental stimuli to emotional (defense) response networks.

2. The major conclusion from studies of fear conditioning is that the amygdala plays

critical role in linking external stimuli to defense responses.

3. Before describing research on the role of the amygdala in fear conditioning, though,

it will be helpful to briefly examine the historical events that preceded modern research on

conditioned fear.

KEYWORDS: emotion; amygdala; limbio system; fear.

THE EMOTIONAL BRAIN IN PERSPECTIVE

In the early part of the twentieth century, researchers identified the hypothalamus

as a key structure in the control of the autonomic nervous system (Karplus and

Kreidl, 1927). On the basis of these early observations, and their own work (Cannon

and Britton, 1925), Cannon and Bard proposed a hypothalamic theory of emotion

that consisted of three major points: (1) the hypothalamus evaluates the emotional

relevance of environmental events; (2) the expression of emotional responses is

mediated by the discharge of impulses from the hypothalamus to the brainstem;