substantia nigra noun1 •A brain structure located in the mesencephalon (midbrain) that plays an important role in reward, addiction, and movement, damage to which occurs in Parkinson's and Parkinsonian patients.Their location was established in the 1950s as the substantia nigra, a layer of grey matter in the midbrain. — 1997 formssubstantia nigras · substantiae nigrae · substantiae nigrae
