Substantia Nigra pars Compacta

The substantia nigra (SN) is positioned in the basal plate domain of the mesencephalon (midbrain). It is divided into superficial (pars reticularis, or SNR) and deep (pars compacta, or SNC) portions. The SNC is populated by dopaminergic neurons (also called the A9 dopaminergic neuron group) that innervate the dorsal striatum (caudet and putamen), participating in movement control. Parkinson's disease is characterized by the death of dopaminergic neurons in this compartment.