The neuroanatomical and neurochemical basis of conditioned fear

After a few pairings of a threatening stimulus with a formerly neutral cue, animals and humans will experience a state of conditioned fear when only t he cue is present. Conditioned fear provides a critical survival-related fu nction in the face of threat by activating a range of protective behaviors. The present review summarizes and compares the results of different labora tories investigating the neuroanatomical and neurochemical basis of conditi oned fear, focusing primarily on the behavioral models of freezing and fear -potentiated startle in rats. On the basis of these studies, we describe th e pathways mediating and modulating fear. We identify several key unanswere d questions and discuss possible implications for the understanding of huma n anxiety disorders. (C) 1999 Elsevier Science Ltd. All rights reserved.