BDNF and Alzheimer disease: It has been reported that levels of BDNF and its receptor TrkB are significantly reduced in brains of patients with mild cognitive impairment or early stages of AD,1, 2 while environmental factors that elevate risks for sporadic AD, such as aging, stress and high-fat diet, impair the BDNF/TrkB signaling pathway.16, 17, 18 In this study, we used TrkB haploinsufficiency as a model to reproduce the TrkB reduction associated with incipient AD, and investigated the mechanisms by which TrkB reduction may trigger or accelerate AD and memory deficits in the 5XFAD mouse model.