substantia nigra substantia nigra the substantia nigra (sn) is a basal ganglia structure located in the midbrain that plays an important role in reward and movement. substantia nigra is latin for "black substance", reflecting the fact that parts of the substantia nigra appear darker than neighboring areas due to high levels of neuromelanin in dopaminergic neurons. parkinson's disease is characterized by the loss of dopaminergic neurons in the substantia nigra pars compacta. substantia nigrasubstantia nigra highlighted in red.section through superior colliculus showing substantia nigra.detailspart ofmidbrain, basal gangliaidentifierslatinsubstantia nigraacronym(s)snmeshd013378neuronames536neurolex idbirnlex_789ta98a14.1.06.111ta25881fma67947anatomical terms of neuroanatomy although the substantia nigra appears as a continuous band in brain sections, anatomical studies have found that it actually consists of two parts with very different connections and functions: the pars compacta (snpc) and the pars reticulata (snpr). the pars compacta serves mainly as a projection to the basal ganglia circuit, supplying the striatum with dopamine. the pars reticulata conveys signals from the basal ganglia to numerous other brain structures. structure coronal slices of human brain showing the basal ganglia, globus pallidus: external segment (gpe), subthalamic nucleus (stn), globus pallidus: internal segment (gpi), and substantia nigra (sn, red). the right section is the deeper one, closer to the back of the head diagram of the main components of the basal ganglia and their interconnections anatomical overview of the main circuits of the basal ganglia, substantia nigra is shown in black. picture shows 2 coronal slices that have been superimposed to include the involved basal ganglia structures. + and – signs at the point of the arrows indicate respectively whether the pathway is excitatory or inhibitory in effect. green arrows refer to excitatory glutamatergic pathways, red arrows refer to inhibitory gabaergic pathways and turquoise arrows refer to dopaminergic pathways that are excitatory on the direct pathway and inhibitory on the indirect pathway.