<Li> The lateral descending pathway consists of the rubrospinal tract originating from the red nucleus responsible for voluntary motor movement, and partially of the lateral corticospinal tract as this tract does not originate or terminate in the tectum but does play a critical role with afferent and efferent motor control along sidetone rubrospinal tract of the tectum . </Li> <P> The ventricular system comprises the choroid plexus, which produces cerebral spinal fluid (CSF), the lateral, third, and fourth ventricles responsible for circulating the CSF . The fourth ventricle is the most caudal aspect of the cerebral ventricular system, and is formed by the pons and medulla . The fourth ventricle is connected to the third ventricle via the cerebral aqueduct, and is the smallest ventricle in the ventricular system . Cerebral spinal fluid originates via the choroid plexus, circulating through the ventricular system and recycled into the subarachnoid space . In the fourth ventricle, CSF is recycled through spinal nerve sheaths through the epidural vein . </P> <Ul> <Li> Midbrain tegmentum </Li> <Li> Crus cerebri </Li> </Ul> <P> The substantia nigra is located in the midbrain, with a left and right region, with two primary regions; the substantia nigra pars compact and the substantia nigra pars reticular . This region contains three of the four primary dopaminergic tracts and is responsible for coordination of eye movement and voluntary motor movement . The region undergoes extremely high metabolic synthesis of dopamine and norepinephrine through the metabolic conversion of tyrosine to L - DOPA via enzymatic reaction Tyrosine Hydroxlyase (cat - 2), to dopamine through Aromatic L - Amino Acid Decarboxylase, and if not used processed further through Dopamine Beta - Hydroxylase into Norepinephrine or Epinephrine via an additional reaction . This region of the brain has been extensively studied in biomedical research due to the loss of dopaminergic neurons in this region contributes to the progression of Parkinson's disease . Currently, there is not a cure for Parkinson's disease but there are short - term effective treatments . Exogenous L - DOPA has been shown to be an effective treatment, however long - term use can result in increased dyskinesia and have deleterious effects on the survival of dopaminergic neurons . Extensive biomedical research is underway after the initiation of the BRAIN initiative formed by the Obama administration in 2013 with the audacious goal of creating cures and preventive measures by 2023 . </P>

Four mounds known as the corpora quadrigemina are found on the dorsal surface of this brain division