Editing Midbrain (section)

===Tegmentum===
[[File:Cn3nucleus-en.svg|thumb|right|Cross-section of the midbrain at the level of the superior colliculus]]
[[File:Midbrain - inferior colliculus.svg|thumb|right|Cross-section of the midbrain at the level of the inferior colliculus.]]

The [[midbrain tegmentum]] is the portion of the midbrain ventral to the cerebral aqueduct, and is much larger in size than the tectum. It communicates with the [[cerebellum]] by the [[superior cerebellar peduncles]], which enter at the caudal end, medially, on the ventral side; the cerebellar peduncles are distinctive at the level of the inferior colliculus, where they [[decussation|decussate]], but they dissipate more rostrally.<ref name="Martin"/> Between these peduncles, on the ventral side, is the [[median raphe nucleus]], which is involved in memory consolidation.

The main bulk of the tegmentum contains a complex synaptic network of neurons, primarily involved in homeostasis and reflex actions. It includes portions of the [[reticular formation]]. A number of distinct [[nerve tract]]s between other parts of the brain pass through it. The [[medial lemniscus]] – a narrow ribbon of fibres – passes through in a relatively constant axial position; at the level of the inferior colliculus it is near the lateral edge, on the ventral side, and retains a similar position rostrally (due to widening of the tegmentum towards the rostral end, the position can appears more medial). The [[spinothalamic tract]] – another ribbon-like region of fibres – are located at the lateral edge of the tegmentum; at the level of the inferior colliculus it is immediately dorsal to the medial lemiscus, but due to the rostral widening of the tegmentum, is lateral of the medial lemiscus at the level of the superior colliculus.

A prominent pair of round, reddish, regions – the [[red nucleus|red nuclei]] (which have a role in motor co-ordination) – are located in the rostral portion of the midbrain, somewhat medially, at the level of the superior colliculus.<ref name="Martin"/> The [[rubrospinal tract]] emerges from the red nucleus and descends caudally, primarily heading to the cervical portion of the spine, to implement the red nuclei's decisions. The area between the red nuclei, on the ventral side – known as the [[ventral tegmental area]] – is the largest [[dopamine]]-producing area in the brain, and is heavily involved in the [[reward system|neural reward system]]. The ventral tegmental area is in contact with parts of the forebrain – the [[mammillary body|mammillary bodies]] (from the [[Diencephalon]]) and [[hypothalamus]] (of the [[diencephalon]]).