Incertal projections from the brainstem and cerebellum: a horseradish peroxidase study in the cat

This study, carried out in the cat, shows the input to the zona incerta (ZI) from the brainstem and cerebellum by means of a retrograde horseradish peroxidase technique. The largest contingent of afferents to the ZI comes from the superior and inferior colliculus, griseum centrale, formatio reticularis mesencephali and nuclei tractus mesencephalici of the nerve trigemini, cuneatus, dentatus and interpositus. Other nuclei such as ruber, lemnisci lateralis dorsalis, raphe magnus, sensorius superior of the nerve trigemini, vestibularis lateralis, reticularis lateralis and reticularis gigantocellularis send moderate projections to the ZI. In addition, a substantial number of brainstem nuclei reach the ZI, but weakly. These anatomical pathways suggest that the ZI might play a role in nociceptive, sensorial, motor, auditive, visual, ingestive and sleep-waking mechanisms.