Figure 2.

The use of multiple biological modalities is rare in machine learning studies of Parkinson’s Progression Markers Initiative data. UpSet plot (Lex et al., 2014; Conway et al., 2017) showing frequencies of different combinations of imaging, CSF, DNA, and RNA data in the machine learning studies we reviewed. Each set of connected dots represents a combination of modalities (bottom). Intersection size is plotted as the number of studies for a particular modality combination (top). The set size is plotted as the overall number of studies using each modality (left). Ninety-two papers used at least one biological modality, including Dopamine Transport imaging striatal binding ratio scores. Thirty studies (out of 110 total) combined multiple biological modalities.