SMN1 and Parkinson disease: Neuroimaging studies of speech production in PD have reported conflicting findings concerning the level of activation in SMA for PD patients compared to controls, with some studies reporting hypoactivation of SMA (Baumann et al., 2018; Narayana et al., 2020), some reporting hyperactivation of SMA (Liotti et al., 2003; Pinto et al., 2004; Rektorova et al., 2007), and others reporting no group differences in SMA activity between PD and controls (Pinto et al., 2011; Arnold et al., 2014; Klobusiakova et al., 2021; Manes et al., 2023).