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 and anxiety, as well as 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 behaviors that mimic natural or conditioned fear.
Lesions of the amygdala block innate or conditioned fear, as well as
various measures of attention, and local infusions of drugs into the
amygdala have anxiolytic effects in several behavioral tests.
N-methyl-D-aspartate (NMDA) receptors in the amygdala may be important in
the acquisition of conditioned fear, whereas 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 to orchestrate parts of the fear