Tectum mesencephali

The tectum (Latin for roof) is the dorsal side of the midbrain.

The position of the tectum is contrasted with the tegmentum, which refers to the region in front of the ventricular system, or floor of the midbrain.

It is involved in certain reflexes in response to visual or auditory stimuli.

The reticulospinal tract, which exerts some control over alertness, takes input from the tectum, and travels both rostrally and caudally from it.

The corpora quadrigemina are four mounds, called colliculi, in two pairs – a superior and an inferior pair, on the surface of the tectum.

The superior colliculi process some visual information, aid the decussation of several fibres of the optic nerve (some fibres remain ipsilateral), and are involved with saccadic eye movements.

The tectospinal tract connects the superior colliculi to the cervical nerves of the neck, and co-ordinates head and eye movements.

Each superior colliculus also sends information to the corresponding lateral geniculate nucleus, with which it is directly connected.

The homologous structure to the superior colliculus in non mammalian vertebrates including fish and amphibians, is called the optic tectum; in those animals, the optic tectum integrates sensory information from the eyes and certain auditory reflexes.

The inferior colliculi – located just above the trochlear nerve – process certain auditory information.

Each inferior colliculus sends information to the corresponding medial geniculate nucleus, with which it is directly connected.