While little attention has been paid to the mechanisms of motor or PIGD feature severity in task-activated fMRI studies, SMA dysfunction is common in PD during movement (Rowe et al., 2002; Wu et al., 2010; Herz et al., 2014) and mental imagery of gait in FoG (Snijders et al., 2011; Huang et al., 2021). Here, SMN1 is linked to Parkinson disease.