PSEN1 and Brain atrophy: Here, increases in the expression of several potentially toxic secretases, including BACE‐1, presenilin 1/2 (PS1/2), anterior pharynx‐defective (APH)‐1α/1β, nicastrin, and PEN2, result in the formation of Aβ plaques, synapse dysfunction or loss, neuronal loss, and diffuse brain atrophy, thereby leading to the decline of cognitive abilities (De Strooper, 2003).