Serial pathways from the prefrontal cortex reach central autonomic structures. Pathways were mapped after injection of the bidirectional tracer BDA in the lateral (LA) hypothalamic area. (A) The first pathway is marked by projection neurons (blue dots) originating most densely from orbitofrontal and medial prefrontal cortices leading to the injection site (brown area in B). (B) The second pathway is marked by labelled axons emanating from the injection site and terminating in several autonomic nuclei (brown lines): (C, D) brainstem nuclei; (E) the thoracic spinal cord; (F) A bidirectional pathway links the amygdala with the same hypothalamic nuclei. The shaded areas in the amygdala show the specific termination zones of axons from orbitofrontal cortex (yellow), and the diffuse termination zone by axons from medial prefrontal cortex (light brown), as described by Ghashghaei and Barbas . The dotted line in A indicates the upper border of cortical layer V, and brown lines show the terminations of hypothalamic axons.