# The Mesencephalon --- The **mesencephalon**, sometimes called the **midbrain** is a part of the [[brainstem]] that has a variety of structures and functions. The **corpora quadrigemina** (or **tectal plate**) has four small paired nuclei called **colliculi** (singular *colliculus*). The two **superior colliculi** are the *[[vision|visual]] reflex centers* which helps the head and eyes track moving objects, and thus respond to visual stimuli. The two **inferior colliculi** are the *[[ears|auditory]] reflex centers* which help the head and eyes track sound, and thus respond to auditory stimuli. The [[basal ganglia|substantia nigra]] are little lumps of black dots, that don't seem really significant, but they are what releases [[dopamine]], and also helps steady your movements. They are part of the [[basal ganglia]] The **red nucleus** are called this because the neurons in this region are rich in [[iron]]. These also help with motor control, and help smoothen your movements. The **cerebral aqueduct** connects the 3th and 4th [[brain ventricles|ventricles]]. ___