New Vistas on Amygdala Networks in Conditioned Fear

• Published in: Journal of neurophysiology 2004-07, Vol.92 (1), p.1-9
• Main Authors: Pare, Denis, Quirk, Gregory J, Ledoux, Joseph E
• Format: Article
• Language: English
• Subjects: Amygdala - physiology; Animals; Conditioning, Classical - physiology; Fear - physiology; Fear - psychology; Humans; Nerve Net - physiology
• ISSN: 0022-3077; 1522-1598
• DOI: 10.1152/jn.00153.2004

1 Center for Molecular and Behavioral Neuroscience, Rutgers State University, Newark, New Jersey 07102; 2 Department of Physiology, Ponce School of Medicine, Ponce, Puerto Rico 00732; and 3 Center for Neural Science, Meyer Building, New York University, New York, New York 10003 Submitted 17 February 2004; accepted in final form 18 February 2004 ABSTRACT It is currently believed that the acquisition of classically conditioned fear involves potentiation of conditioned thalamic inputs in the lateral amygdala (LA). In turn, LA cells would excite more neurons in the central nucleus (CE) that, via their projections to the brain stem and hypothalamus, evoke fear responses. However, LA neurons do not directly contact brain stem-projecting CE neurons. This is problematic because CE projections to the periaqueductal gray and pontine reticular formation are believed to generate conditioned freezing and fear-potentiated startle, respectively. Moreover, like LA, CE may receive direct thalamic inputs communicating information about the conditioned and unconditioned stimuli. Finally, recent evidence suggests that the CE itself may be a critical site of plasticity. This review attempts to reconcile the current model with these observations. We suggest that potentiated LA outputs disinhibit CE projection neurons via GABAergic intercalated neurons, thereby permitting associative plasticity in CE. Thus plasticity in both LA and CE would be necessary for acquisition of conditioned fear. This revised model also accounts for inhibition of conditioned fear after extinction. Address for reprint requests and other correspondence: D. Paré, CMBN, Rutgers State University, 197 University Ave., Newark, NJ 07102 (E-mail: pare{at}axon.rutgers.edu ).