From these reports, it is suggested that while the reduction of BDNF levels in the hippocampus may play a pivotal role in the impaired EFM, increase in BDNF levels may be associated with enhanced fear memory in PTSD, though no relationship between hippocampal BDNF levels and the impaired fear memory has been demonstrated in humans. The gene discussed is BDNF; the disease is post-traumatic stress disorder.