BDNF and early-onset autosomal dominant Alzheimer disease: Diverse and region-specific dysregulation of BDNF-TrkB signaling has been observed in many neuropsychiatric disorders such as Alzheimer’s disease (AD), Parkinson’s disease, Amyotrophic Lateral Sclerosis (ALS), Huntington’s disease, epilepsy, stroke, mood disorders and schizophrenia.