The results in the research article were obtained with a rat model of Parkinson's, where Parkinsonian symptoms are induced with rotenone. Most models of Parkins

The results in the research article were obtained with a rat model of Parkinson's, where Parkinsonian symptoms are induced with rotenone. Most models of Parkinson's are based on neurotoxic drugs (e.g. MPTP, first discovered to induce Parkinsonian symptoms in heroin addicts) so they're kind of the best we can do. (there's also genetic models--e.g. mice that express chronically low levels of dopamine. But basically other animals don't get Parkinson's in the wild as far as we can tell.) There's a summary of the evidence for the rotenone model in the discussion of the paper itself, and the paper is in an open access journal so you can read it should you so desire: http://actaneurocomms.biomedcentral.com/articles/10.1186/s40478-016-0346-z http://actaneurocomms.biomedcentral.com/articles/10.1186/s40... There is something of merit here if there's any reason to believe that actual Parkinson's patients show similar retinal degeneration far before they show any other symptoms. The authors don't mention any evidence for that...so I'm guessing there's not any. Either they are wildly scrambling to find some, or a cynic might suggest they looked already in humans and didn't find any, so they published this instead. A paper showing multiple lines of evidence supporting their theory in a rodent model and in a patient population would probably have been a home run that got them into a glam mag.