The zona incerta: another source of centrifugal fibers to the main olfactory bulb

Neurons in the ipsilateral anteropolar division of the zona incerta were retrogradely labeled following injections of horseradish peroxidase in the main olfactory bulb. In addition, labeled cell bodies were found in the dorsal hypothalamus. Fewer and less densely labeled neuron cell bodies were seen in the contralateral zona incerta and dorsal hypothalamus. Most of the cells had a characteristic fusiform shaped soma, but a small number of the hypothalamic cells had spherical or conical shaped cell bodies.