These observations appear consistent with GAD67 expression being restricted to immature GCs since (1) most dentate gyrus GCs are not fully mature at birth and undergo postnatal differentiation (Altman and Bayer, 1990), (2) the number of newborn neurons decreases with age (Kempermann et al., 2004) and (3) epilepsy is known to stimulate adult neurogenesis in the dentate gyrus (Jessberger et al., 2007; Parent, 2007). Here, GAD1 is linked to epilepsy.