Interestingly, Palop et al. (2005) found that basal and activity-induced Arc transcript level was reduced particularly in the dentate gyrus of hAPPFAD mice; in this transgenic AD model, exploration of a novel environment significantly increased Arc expression and Arc IR levels in the pyramidal layer and stratum radiatum at CA1, and in the neocortex (as in non-transgenic controls), but not in granule cells of the dentate gyrus (at variance with controls). This evidence concerns the gene ARC and Alzheimer disease.