Superior colliculus

The superior colliculus (Latin, higher hill) is a paired structure that is part of the brain's tectal area. The two superior colliculi sit below the thalamus and surround the pineal gland in the mesencephalon of vertebrate brains. It comprises the rostral aspect of the midbrain, posterior to the periaqueductal gray and adjacent superior the inferior colliculus. The inferior and superior colliculi are known collectively as the corpora quadrigemina (Latin, quadruplet bodies).

In humans, the superior colliculus (SC) is involved in the generation of saccadic eye movements and hand-eye coordination. Afferents to the SC originate in the cerebral cortex, inferior colliculus, retina, basal ganglia, and spinal cord. Efferents project to the paramedian pontine reticular formation, spinal cord, and elsewhere. In humans, as in most larger vertebrates, sensory information that goes to the mesencephalon will be relayed via the thalamus to the cerebral cortex for interpretation. However, the SC can also mediate some oculomotor movements without cortical involvement.

The SC receives visual, as well as auditory, inputs in its superficial layers, and the deeper layers of the colliculus are connected to many sensorimotor areas of the brain. The colliculus as a whole is thought to help orient the head and eyes toward something seen and heard.

In echolocating bats, the SC has been shown to influence vocalization parameters and ear movements, both orienting components of the bat's biosonar system, thereby assisting in orienting movements.

The comparable area of the mesencephalon of non-mammalian vertebrates is called the optic tectum. In amphibians, reptiles, and fish, the optic tectum is the largest visual processing area, though its function remains largely unknown. It seems to be required for predator/prey discrimination leading to escape or hunting behavior respectively. In contrast, the role of the SC for visual discrimination is less prominent in more complex vertebrates.