Suffering from delusions was one of the symptoms Susannah experienced from her condition that we discussed in class. One of the delusions that I found particularly interesting was her being unable to emotionally recognize her father. She was convinced that although the man in front of her looked exactly life her father, he was not her father but an imposter. This condition is known as Capgras delusion.
Capgras delusion is separate from face blindness or prosopagnosia where faces don’t recognize faces. Capgras subjects can recognize a familiar face, but can’t understand their connection emotionally with the person so as a result they feel as if the person is an imposter. This disorder first described in 1923 by Joseph Capgras can be related to several causes. It has been linked with paranoid schizophrenia, which was one of the considered diagnoses for Susannah. It is also observed in patients with dementia, brain injury, and neurodegenerative diseases. The presence of these delusions makes it clear that there is a problem with Susannah’s brain.
Capgras could be connected to cerebral dysfunction in some way either due to trauma, lesion, or disease. It is often seen in patients with other psychiatric disorders and epilepsy. It could be due to a memory management problem in addition to a communication problem connecting memory of faces and emotional memory. The brain being unable to connect these things looks for a reason that there is no emotional response to a familiar face may explain it as the person being an imposter. This suggests that it could involve problems in the prefrontal cortex, limbic system, or temporal lobe areas.
This is a TED talk by Ramachandran, a well-known neuroscientist, who explains the syndrome and some of the biological reasoning behind the psychology
On Psychology and Neuroscience 