Capgras Delusion, or Syndrome is a disease in which a person believes that an individual close to them such as a spouse, family member, or friend has been taken over by someone else who looks exactly like them, and impostor per say. The onset of Capgras Delusion has been connected to a brain injury or accident and also with the diagnosis of Paranoid Schizophrenia. The loop hole with Capgras Syndrome seems to be that in certain cases the individual with the disease may not be able to recognize their loved one by looking at their face, but when hearing their voice alone, they believe they are truly the same person. For example, if an individual with Capgras Syndrome saw a friend in person, they would believe that their body was inhabited by an impostor. If the friend was talking to the diseased individual on the phone, they would believe the person is who they say they are.
Here is a video of a man who was in a serious car accident and when he woke up from a deep coma, they discovered he did not recognize his mother or father.