SNCA and Parkinson disease: The models using uniform transcription profiles underperformed compared to those using empirical transcription profiles (Fig 6, red = empirical gene expression; blue = uniform gene expression); in other words, the incorporation of true local differences in gene expression improves model fit, suggesting that the atrophy pattern in PD is not solely explained by pathogenic spreading per se but also depends on local vulnerability, here dependent on α-synuclein concentration.