Post-mortem human brain histology demonstrates that, when the motor symptoms of PD manifest, ~70% of the SNpc DA cells have degenerated (37) together with a marked loss of choline acetyltransferase (ChAT) expressing neurons in the nucleus basalis of Meynert and penduncolopontine nucleus (PPT) and reduced cortical and striatal cholinergic activity (38). This evidence concerns the gene CHAT and Parkinson disease.