This oxidation may be relieved by neuromelanin. Patients with Parkinson's disease had 50% the amount of neuromelanin in the substantia nigra as compared to similar patients of their same age, but without Parkinson's. The death of neuromelanin-containing neurons in the substantia nigra, pars compacta, and locus coeruleus have been linked to Parkinson's disease and also have been visualized "in vivo" with neuromelanin imaging. Neuromelanin has been shown to bind neurotoxic and toxic metals that could promote neurodegeneration. Dark pigments in the substantia nigra were first described in 1838 by Purkyně, and the term neuromelanin was proposed in 1957 by Lillie, though it has been thought to serve no function until recently. It is now believed to play a vital role in preventing cell death in certain parts of the brain. It has been linked to Parkinson's disease and because of this possible connection, neuromelanin has been heavily researched in the last decade.