[UW Anatomy |
Contents]
Function:
Superior and inferior colliculi comprise the tectum or roof (dorsal
to the cerebral aqueduct) of the mesencephalon or midbrain. The
rostral portion of the roof consists of two bumps=superior colliculi.
Superior colliculus is thought to play a role in integrating sensory
information (visual, auditory, somatosensory) into motor signals that
help orient the head toward various stimuli.
Pathway:
Visual inputs from the retina (retinocollicular) and the visual
cortex (corticocollicular) reach the superficial layers of this
laminated structure. Visual inputs from the right visual world reach
the LEFT superior colliculus, and vice-versa. Auditory and
somatosensory inputs also reach intermediate and deep layers (don't
worry about how these inputs get there!). Axons that arise from cells
in the intermediate and deep layers CROSS at the level of the
superior colliculus, pass caudally through the brainstem (we do not
identify them in our sections) and enter the VENTRAL FUNICULUS of the
spinal cord. Tectospinal axons leave the ventral funiculus to synapse
upon cells in the medial part of the spinal cord grey at upper
cervical levels only. Pathway helps us to turn our head toward visual
(and auditory and somatosensory) stimuli. The LEFT superior
colliculus tells the RIGHT cervical cord motor neurons (splenius
capitus, not sternocleidomastoid) to turn the head the to the right.
Deficits:
Lesion of the LEFT superior colliculus results in inability to turn
head reflexively to the RIGHT (CONTRA.) upon visual (or somatosensory
and auditory) stimuli on the RIGHT.
Other Note:
Superior colliculus is also involved in the control of eye movements.