(a) MR image showing sites of gadolinium-saline infusions (white hypersignal) in area 13. A gadolinium-saline solution was infused to a site just dorsal to the intended target to confirm accurate placement of the cannulae before data collection began. (b) Photograph of ventral view of brain showing locations of retrograde tracer injections made at the end of the experiment to reconfirm target locations. Numerals correspond to sections illustrated in (c) and (d). Red outlined region illustrates site of injection of cholera toxin subunit B (CTB), as reconstructed after histological processing of tissue. Yellow outlined region illustrates site of injection of Fast Blue, which appears yellow before processing. (c) and (d). Line drawings of coronal sections through the anterior OFC (area 11) (c) and the posterior OFC (area 13) (d). Red-shaded region corresponds to CTB tracer injection. Blue-shaded region corresponds to Fast Blue injection. Scale bar applies to both c and d. Compare and contrast with Figure 1. Abbreviations: cd, caudate nucleus; ps, principal sulcus; as, arcuate sulcus; 11l, 11m, 12m, 12r, 12o, 13m, and 13b, cytoarchitectonic divisions of the prefrontal cortex (Carmichael and Price, 1994).