In order to demonstrate the impact of the RG choice on RT-qPCR data normalization, target gene GSK3B expression levels were analysed in both the PFC and the CB, between NCs and AD (Fig. 4A,B), NCs and PD (Fig. 4C,D), as well as between all groups (Fig. 4E–J). This evidence concerns the gene GSK3B and Parkinson disease.