Superior colliculus

The superior colliculus (Latin for upper hill) is a structure lying on the roof of the mammalian midbrain.

In non-mammalian vertebrates, the homologous structure is known as the optic tectum, or optic lobe.

The adjective form tectal is commonly used for both structures.

In mammals, the superior colliculus forms a major component of the midbrain.

It is a paired structure and together with the paired inferior colliculi forms the lamina quadrigemina.

The superior colliculus is a layered structure, with a pattern that is similar to all mammals.

The layers can be grouped into the superficial layers (stratum opticum and above) and the deeper remaining layers.

Neurons in the superficial layers receive direct input from the retina and respond almost exclusively to visual stimuli.

Many neurons in the deeper layers also respond to other modalities, and some respond to stimuli in multiple modalities.

The deeper layers also contain a population of motor-related neurons, capable of activating eye movements as well as other responses.

In other vertebrates the number of layers in the homologous optic tectum varies.

The general function of the tectal system is to direct behavioral responses toward specific points in body-centered space.

Each layer contains a topographic map of the surrounding world in retinotopic coordinates, and activation of neurons at a particular point in the map evokes a response directed toward the corresponding point in space.

In primates, the superior colliculus has been studied mainly with respect to its role in directing eye movements.