Monday, June 13, 2011

Superior Colliculus

The superior colliculus is a paired structure that forms a rostral lump on each side of the dorsal part of the midbrain. It is a highly layered structure which functions as a visual, motor, and sensory reflex center. The two superior colliculi sit below the thalamus and surround the pineal gland in the mesencephalon of vertebrate brains. It comprises the caudal aspect of the midbrain, posterior to the periaqueductal gray and immediately superior to the inferior colliculus. The inferior and superior colliculi are known collectively as the corpora quadrigemina.

The first three superficial layers of the superior colliculus receive visual information primarily from two sources: the retina (retinocollicular) and the visual cortex. In contrast to the exclusively visual nature of the superficial layers, the intermediate and deep layers receive projections from many functionally different areas of the brain. These inputs are both "motor" and "sensory". Since the latter category includes visual, auditory and somatosensory inputs, the superior colliculus is not exclusively related to visual function. Instead, it plays a role in helping orient the head and eyes to all types of sensory stimuli.