FOS and Parkinson disease: We believe that the abnormalities in SPN activity in the DA-denervated dorsal striatum in Pitx3Null mice reported in this study likely occur in other PD models with more expansive DA denervation and PD brains, as reflected in similar molecular changes such as D1R and D2R hyperfunctionality, c-fos and pERK expression in dMSNs in PD brains and 6-OHDA DA-lesioned brains and Pitx3Null brains (Pifl et al., 1992; Corvol et al, 2004; Hwang et al., 2005; Santini et al., 2010; Ding et al., 2015).