Recently, we reported that 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced PD model mice (PD mice) showed facilitation of hippocampal memory extinction via reduced cyclic adenosine monophosphate (cAMP)/cAMP-dependent response element-binding protein (CREB) signaling in the hippocampus, which may cause cognitive impairment in PD [5,6]. This evidence concerns the gene CREB1 and Cognitive impairment.