The superior colliculus, (Latin, upper hill) is a paired structure of the mammalian midbrain. In other vertebrates this is known as the optic tectum or simply tectum, and the adjective tectal may also be used. The superior colliculus forms a major component of the midbrain.The tectum is a layered structure, with a number of layers that varies by species. The superficial layers are sensory-related, and receive input from the eyes as well as other sensory systems.n mammals, and especially primates, the massive expansion of the cerebral cortex reduces the tectum (superior colliculus) to a much smaller fraction of the whole brain.