Another variable that might influence the training effect or group differences in the baseline cognitive performance is the polymorphism of the dopaminergic gene LMX1A, since those with the AA genotype showed greater training effects than those with the AG/GG genotypes after WM training, both in healthy individuals (Bellander et al., 2011) and in those with HIV-infection (Chang et al., 2017). Here, LMX1A is linked to HIV infectious disease.