Neuronatomy of conditioned fear. A simplified neuroanatomical schematic outlining some of the major brain regions and their anatomical connections invoved in Pavlovian fear conditioning. Shading indicates major brain regions (brown, midbrain; yellow, thalamus; orange, basal forebrain; blue, neocortex; red, amygdala; violet, hippocampus). Sensory information asends to the amygdala through the midbrain and thalamus; auditory information also reaches the amygdala via the cortex. Antomical convergence and association of of the conditioned stimulus (CS) and unconditioned stimulus (US) occurs in the amygdala; contextual information processed by the hippocampus can also enter into association with the US in the amygdala. Conditioned and unconditioned fear responses (CRs and URs) are mediated by projections from the amygdala to an array of brain areas involved in autonomic and somatic defensive responses. Abbreviations: AC, auditory cortex; BA, basal nuclei of the amygdala; BNST, bed nuclei of the stria terminalis; CEl, lateral division of central nucleus of the amygdala; CEm, medial divsion of the central nucleus of the amygdala; HIP, hippocampus; IC, inferior colliculus; IL, infralimbic division of the medial prefrontal cortex; ITC, intercalated cellsof the amygdala; LA, lateral nucleus of the amygdala; LH, lateral hypothalamus; MGdv, dorsal and ventral divisions of the thalamic medial geniculate nucleus; MGm, medial division of the thalamic medial geniculate nucleus; NAcc, nucleus accumbens, dlPAG, dorsolateral division of the periaqueductal gray; vPAG, ventral division of the periaquedcutal gray; PIN, posterior intralaminar nucleus of the thalamus; PL, prelimbic division of the medial prefrontal cortex; PRh, perirhinal cortex; PVN, paraventricular nucleus of the hypothalamus.