Part 2 - Capgras Delusion

In the last post, I introduced the special area of the brain called the fusiform gyrus and its role in human face recognition.  Today I would like to talk about how much this area is hardwired into the emotional centers of the brain, the limbic system.  There are two fascinating conditions that illustrate  the intimate connection between recognizing faces and our feelings of emotion.  First off is Prosapagnosia which I introduced last time as the inability to recognize human faces.  The interesting connection to the emotional centers of the brain is evidenced by the fact that some patients will have the proper emotional response to photographs despite having no conscious awareness of the person in the picture.  So if you show a prosapognosiac patient a photograph of their mother, they might insist that they have no idea who is in the picture, but all the while be having the correct emotional response.  Similarly if you showed them a picture of someone like Osama Bin Laden.  So our conscious awareness and our emotional reaction to faces might be distinct and separate.  How many times have you had some feeling about someone that you meet despite having no conscious memory of ever meeting that person?   Whether it’s longing or aversion that feel, listen closely because that could just be your fusiform gyrus speaking to your limbic system. 

The next even more fascinating condition is called Capgras syndrome (or delusion).  In this condition, facial recognition is intact but the connection between the fusiform gyrus and the emotions is disrupted.   So these patients can recognize faces, but they do not have the emotional response to the people that they recognize.  This creates a cognitive conflict in their minds.  They have a intellectual idea that this person is their mother for instance, but since they do not have the correct emotional reaction, their brains must reconcile the apparent conflict.  The way the conflict is reconciled in these patients is that they become convinced that their loved one has been replaced somehow by an exact replica of themselves (a robot, alien, or some sort of evil twin).   The delusion can be so convincing that some patients have even harmed loved ones convinced that they were imposters.  Both of these conditions show how the brain is not only hardwired to recognize faces, but how facial recognition has a direct impact on our emotions whether we are conscious of it or not.  When we look at faces, we don’t just recognize them with our brains, but we react to them with our hearts and emotions.