SUBSTANTIA NIGRA Heterogeneous portion of the middecephalus and important part of the basal ganglia system . . The compact part contains neurons that in humans are dyed black with the neuromelanin pigment that decreases with age. The compact part is usually divided into ventral floor and dorsal floor; the latter is calbindine positive. The function of dopaminergic neurons in the compact part of the black substance is complex, and seems related to learning. The degeneration of pigmented neurons in this region is causing Parkinson's disease. Some synonyms, words or similar expressions may be locus niger, black substance
