Superior colliculus

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Brainstem and related structures.

The superior colliculus is a mass of gray matter found in the tectum (roof) of the rostral midbrain. It is a paired structure that sits just posterior to the periaqueductal gray and anterior to the inferior colliculus. It plays a vital role in processing visual information and initiation of reflexive eye and head movements.

The superior colliculi receive inputs from various regions including the retina, spinal cord, inferior colliculi, occipital and temporal cortices. Specifically, it receives direct signals from retinal ganglion cells, the primary visual cortex and other visual-associated regions, somatosensory inputs and auditory inputs primarily from the inferior colliculi, allowing for multisensory integration.

The superior colliculi project efferent axons to multiple areas, notably the pulvinar of the thalamus and to several other sites in the brainstem and spinal cord to help direct visual attention and regulate eye movements.

Histologically, each superior colliculus is organized into three main layers with subdivisions that reflect its various inputs and outputs: 

• The superficial layer mainly processes visual information.
• The intermediate layer is important in sensorimotor integration.
• The deep layer facilitates multisensory integration.

The superior colliculi, together with the two caudal inferior colliculi are collectively referred to as the corpora quadrigemina (quadrigeminal bodies).