Consistent with our findings, hippocampal BDNF expressions and levels were found to be lower in rodent PD models, which was associated with hippocampal functions impairment in both electrophysiologically and behaviorally (Darbinyan et al. 2017; Zhu et al. 2011; Alzoubi et al. 2018). This evidence concerns the gene BDNF and Parkinson disease.