Corpora quadrigemina – the largest nuclei
–Divided into the superior and inferior colliculi
•Superior colliculi – nuclei that act in visual reflexes
•Inferior colliculi – nuclei that act in reflexive response to sound
•Periaqueductal gray matter surrounds the cerebral aqueduct
–Involved in two related functions
•Fright-and-flight reaction
•Mediates response to visceral pain