Post-traumatic stress disorder can affect both humans and animals. When animals experience trauma, they may physically shake to discharge the energy from the event. If they are unable to do this, the animal is at risk of death. The amygdala region of the brain holds memories of terrifying events that can lead to PTSD in both animals and humans. Brain imaging has shown that PTSD suppresses neurogenesis in response to threats like predators that trigger fears related to past trauma.