Numerous prior studies have shown that SMA functioning is affected in patients with PD (Jenkins et al., 1992; Playford et al., 1992; Rascol et al., 1992, Rascol et al., 1994; Jahanshahi et al., 1995; Haslinger et al., 2001; Grafton et al., 2006; Heinrichs-Graham et al., 2014b, 2014a). Here, SMN1 is linked to Parkinson disease.