Monthly Archives: August 2005

Mysteries of the Brain Part – 13 – CAPGRAS SYNDROME

This post was written on Wed, 31 Aug 2005.




       This part is inspired by a chapter I read in the book “Phantoms in the Brain” by V.S Ramachandran which Harindranath Parameswaran gave me to read.

       When we recognize a person we feel close to, do we just match the face of the person with the image we have in the brain? Or is there a
more emotional complicated process?

       There is a disease called the Capgras syndrome. A person suffering from this syndrome remembers the face of everyone he is closely related to him, just like all of us. But when he meets that person he refuses to accept that he is related to that person. He thinks that that person is just an imposter with the same face. For example when a person suffering from Capgras syndrome meets his own father he cannot believe that he is actually meeting his father. He may think that the person is someone else with the same face as his father and is posing as the father. So
people with this disease think that they are surrounded by imposters who pose as people close to him. There is nothing wrong with their ability to
recognize faces and their memory is normal too- there is something deeper that is wrong!

       Ramachandran decided to do some experiments with people who have this problem. He decided to place electrodes on the hands of these people and then show pictures of people closely related to them.


       But before we go to this experiment lets understand what results a normal person would show under similar circumstances. If we meet a person we are emotionally related to our hands become sweaty! They will become slightly sweaty. You wont even know but this small amount of sweat is enough to change the conductivity of the skin and the electrodes to show spikes in the recording. You cannot hide this effect. It is in the
subconcious. And that is how a lie detector works. They ask a question. If you lie you become very slightly nervous and you hands become sweaty and the electrode shows a spike. So all emotional responses cause a change in conductivity of the skin and can be caught by electrodes!

       Now lets get back to the experiment with Capgras syndrome sufferers. When electrodes were placed in the hand and pictures of people
close to them were shown there was no electrical response. They could identify the names of the people and their relationship to them but there
was no emotional impulse!


       And that tells us how we recognize people around us. We dont just do a feature by feature comparison of the person with the picture in the
memory. That is what dumb computers do! We also associate emotions with the face that we see. If the emotional aspect is removed then we may recognize the face but we refuse to  accept the person as someone we know!
That is what happens in the Capgras syndrome.

        But how does this happen. Lets see what happens when we meet a person the first time. Lets say we meet a person X. We form a memory of that person. If we meet him again a few weeks later we add to the previous memory and so on. So if we meet X several times we have a category of the person X in the brain with the related memories and our feelings about X. Now lets look at this in detail: whenever we meet X we retreive the category X and the associated memories and we add the new memories to the category X. This is what happens in a normal brain.

       Now lets imagine a different scenario: We have met X several times and have several memories and emotions associated with X. Now lets say there is a damage to the retrival portion of our brains. When we meet X again we cannot retreive the category of X. So we meet X as though he is a complete stranger and we create a new category for X. Therefore we have two categories for X: one that we formed before the accident and another we formed after the accident. Since there is no problem with the recognition aspect of the brain we know that the two Xs look the same but somehow we are unable to associate old memories and emotions with the X we meet now. The two X categories are completely distinct from each other.

       And that is what happens in Capgras syndrome. The person has two memories for  his father for example. First is  the one that was formed
before the disease started. In these memories the father is the father. These memories are packed with emotions. After the disease the old
memories could not be retreived so a new category was formed for the person who is the father. These new memories are devoid of emotions
because those emotions that are reserved for the father are already allocated to the old memories of the father. The “new” father seems like
an imposter who looks like the person’s father but is not!

       Diseases of the brain are general very severe and painful. But through the study of these diseases we can get to know how the brain actually works. So these rare imperfections in the brain show us how perfect the human brain is!!!!

       And here is a beautiful Christina Rossetti poem about remembring and forgetting. I hope reading this poem changes the conductivity of
your skin:

               Remember me when I am gone away
               Gone far away into the silent land;
               When you can no more hold me by the hand,
               Nor I half turn to go yet turning stay.

               Remember me when no more day by day
               You tell me of our future that you planned:
               Only remember me; you understand
               I will be late to counsel then or pray.

               Yet if you should forget me for a while
               And afterwards remember, do not grieve:
               For if the darkness and corruption leave
               A vestige of the thoughts that once I had,
               Better by far you should forget and smile
               Than that you should remember and be sad.



 Go, wondrous creature! mount where Science guides:
 Go, measure earth, weigh air, and state the tides:
 Instruct the planets in what orbs to run,
 Correct old time and regulate the Sun;