Topographic organization of bidirectional connections between the cingulate region (infralimbic area and anterior cingulate area, dorsal part) and the interbrain (diencephalon) of the adult male rat.

The medial prefrontal cortex [ (Brodmann, 1909) (CNG)] in the rat is a connectionally and functionally diverse structure. It harbors cerebral nuclei that use long-range connections to promote adaptive changes to ongoing behaviors. The CNG is often described across functional and anatomical gradients, a dorsalventral gradient being the most prominent. Topographic organization is a general feature of the nervous system, and it is becoming clear that such spatial arrangements can reflect connectional, functional, and cellular differences. Portions of the CNG are known to form reciprocal connections with cortical areas and thalamus; however, these connectional features have not been described in detail or mapped to standardized rat brain atlases. Here, we used co-injected anterograde ( leucoagglutinin) and retrograde (cholera toxin B subunit) tracers throughout the CNG to identify zones of reciprocal connectivity in the diencephalon [or (Baer, 1837) (IB)]. Tracer distributions were observed using a Nissl-based atlas-mapping approach that facilitates description of topographic organization. This draft report describes CNG connections of the (Rose & Woolsey, 1948) (ILA) and (Krettek & Price, 1977) (ACAd) throughout the IB. We found that corticothalamic connections are predominantly reciprocal, and that ILA and ACAd connections tended to be spatially segregated with minimal overlap. In the (Kuhlenbeck, 1927), we found dense and specific ILA-originating terminals in the following atlas territories: (Swanson, 2004) (LHAd) and (Swanson, 2004) (LHAs) of the (Nissl, 1913), (Wang & Zhang, 1995) (PSTN), (Petrovich et al., 2001) (TUte), and an ill-defined dorsal cap of the (Gudden, 1881) (MM). We discuss these findings in the context of feeding behaviors.