However, it has been shown that exposure to enriched environment increased the hippocampal neurogenesis (19, 20), dopamine transporter protein in the nucleus accumbens (27) and also facilitated spatial learning and memory through glutamate AMPA receptor mediation (28) and the hippocampal astroglial pathological changes in Alzheimer's disease (29). Here, SLC6A3 is linked to early-onset autosomal dominant Alzheimer disease.