Colliculi

At the top of the midbrain are the colliculi, which derives its name from the Latin word for 'hill.It contains two areas named after specific colours: the iron-rich red nucleus (which actually looks pink) is involved in the coordination of movements; the periaqueductal grey is a dense region of grey matter and is involved in suppressing pain.Sandwiched between these bundles and the tegmentum is a layer called the substantia nigra, a darkly pigmented cluster of neurons with cells (containing melanin) that make the neurotransmitter dopamine; this layer of neurons is an important relay station for nerve signals of the CNS systems that coordinate our movements.It contains two pairs of bulging, layered bundles of neurons called the superior and inferior colliculi.The tegmentum in the midbrain also contains connections that play a role in keeping us alert.