The results obtained in many postmortem studies in AD patients indicated decreased level of neurotrophin like brain derived neurotrophic factor (BDNF) (decreased level of mRNA and pro-BDNF (precursor of BDNF) and mature BDNF) and neural growth factor (NGF) (increased level of NGF precursor (pro-NGF) and decreased level of NGF) in brain regions like basal forebrain or hippocampus whose functions are impaired in AD. The gene discussed is BDNF; the disease is Alzheimer disease.