Connections between the zona incerta of the dog diencephalon and the substantia nigra, ventral tegmental field, and pedunculopontine tegmental nucleus.

Studies using technique based on retrograde and anterograde transport of horseradish peroxidase were performed to address the organization of the connections of different sectors of the zone incerta (ZI) of the diencephalon with substructures of the substantia nigra, ventral tegmental field, and pedunculopontine nucleus of the midbrain in dogs. These structures were found to be interconnected. The organization of these connections included elements demonstrating that segregated conduction of functionally diverse information can be transmitted via these pathways. In addition, the convergence of projections fibers from neurons in substructures of the midbrain nucleus described in all sectors of the ZI and to these neurons from neurons in all ZI sectors is evidence that functionally diverse information can be integrated both at the level of the ZI and at the level of the midbrain structures studied here.