Garzon et al. (2002) showed that BDNF mRNA levels were lower in parietal cortex of AD patients (Garzon et al., 2002). A postmortem study of AD brains also found reduced protein levels of BDNF in the hippocampus and cortex (Du et al., 2018). In addition, another study reported decreased TrkB expression in the frontal and temporal cortex of AD brains (Allen et al., 1999). The gene discussed is NTRK2; the disease is Alzheimer disease.