CONNECTIONS OF THE POSTERIOR PALLIUM IN THE CRESTED NEWT, TRITURUS-CARNIFEX

The connections of the posterior pallial regions were studied in the c rested newt, Triturus carnifex, by means of the horseradish peroxidase technique. The tracer was injected into the lateral and medial pallia , caudal to the interventricular foramen. In addition, the connections between the posterior pallium and the infundibular hypothalamus were investigated with both horseradish peroxidase and the fluorescent dye DiI. The results show important differences between the connection pat terns of the medial and lateral pallia. The lateral pallium receives i nputs from the main olfactory bulb and send fibers to the contralatera l hemisphere through the anterior commissure. It also shows modest ext ra-telencephalic connections. Conversely, the medial pallium receives direct afferent inputs from the amygdala (pars medialis) and the anter ior dorsal thalamus. It is reciprocally connected to the contralateral homologue region through the hippocampal commissure, and its main eff erent system is the medial forebrain bundle, which reaches the infundi bular hypothalamus. The infundibulum also receives a prominent project ion from the amygdala (pars lateralis). The connectivity of the poster ior pallium is comparable to that reported previously for the anterior pallium, although a few differences are noted. These differences in t he connectivity of the lateral pallium and the medial pallium may refl ect different functional properties of these telencephalic regions.