1. In the brain, the corpora quadrigemina are the four colliculi—two inferior, two superior—located on the tectum of the dorsal aspect of the midbrain. They are respectively named the inferior and superior colliculus. The corpora quadrigemina are reflex centers involving vision and hearing. (wikipedia.org)
Word origin: Latin quadri = four, and gemini = paired or twinned; hence four-fold.