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. Author manuscript; available in PMC: 2011 Apr 1.
Published in final edited form as: Curr Opin Neurobiol. 2010 Mar 18;20(2):231–235. doi: 10.1016/j.conb.2010.02.005

Figure 1. Prefrontal control of fear expression and extinction.

Figure 1

During fear expression (left) and extinction (right) of auditory fear conditioning, tone responses from the amygdala (amyg) get integrated by the prelimbic (PL) or infralimbic (IL) prefrontal cortex with converging information from diverse sources such as hippocampus (Hipp), brainstem monoamines (Bstm), mediodorsal thalamus (MD), and orbital prefrontal cortex (OFC) to determine whether or not to produce a fear response. Fear excitation involves PL projections back to basal amygdala (BA), whereas fear inhibition involves IL projections to amygdala intercalated cells (ITC). In turn, BA excites neurons in the medial division of the central nucleus of the amygdala (CeM) to produce fear responses, while ITCs inhibit these amygdala output neurons thereby inhibiting fear responses. Thus, the same conditioned stimulus (e.g. a tone) signals either high fear (red) or low fear (green) states in the appropriate circumstances.