Different lateral amygdala outputs mediate reactions and actions elicited by a fear-arousing stimulus

Amorapanth, P., LeDoux, J.E., & Nader, K. (2000). Different lateral amygdala outputs mediate reactions and actions elicited by a fear-arousing stimulus. Nature Neuroscience, 3, 1, 74-79.

One common reaction to threat is elicitation of unlearned species-typical defense reactions. Another is the ability to take novel actions in threatening situations, which may also prove advantageous. In escape-from-fear (EFF) tasks, animals come to learn that an arbitrary response (e.g. stepping into the adjoining chamber) terminates a CS which predicts shock. Authors placed lesions throughout the fear circuit to see try to elucidate function. Lateral amygdala (LA) is believed to be the sensory interface where CS information enters the amygdala; lesions here block acquisition of both conditioned freezing responses, as expected, but also block acquisition of the CS's reinforcement of a new response in the EFF task. Central nucleus (CE) lesions block expression of hard-wired motoric output (i.e. freezing itself), but not the EFF. Basal nucleus (B) lesions had no effect on conditioned freezing, but did block the EFF. By way of interactions between the B and striatal circuits, reinforcement in the amygdala may come to reinforce novel motor responses. Thus, it may be that activation of LA by a CS triggers a reactive response output system via the CE and an active output system via the B.