Cortico-amygdala circuits: role in the conditioned stress response.

The amygdala plays a crucial role in the orchestration and modulation of the organism response to aversive, stressful events. This response could be conceived as the result of two interdependent components. The first is represented by sets of visceral and motor responses aimed at helping the organism to cope with the present event. The second is the acquisition and modulation of memories relative to the stressful stimulus and its context. This latter component contributes to the instatement of conditioned stress responses that are essential to the capability of the organism to predict future exposures to similar stimuli in order to avoid them or counteract them effectively. In the amygdala, these two components become fully integrated. Massive networks link the amygdala to the hypothalamus, midbrain and brainstem. These networks convey visceral, humoral and nociceptive information to the amygdala and mediate its effects on the hypothalamic-pituitary-adrenal axis as well on autonomic and motor centers. On the other hand, interactions between the amygdala and interconnected cortical networks play a crucial role in acquisition, consolidation and extinction of learning relative to the stressful stimulus. Within the scope of this review, current evidence relative to the interaction between the amygdala and cortical networks will be considered in relationship to the integration of the conditioned response to stress.