He’s the old gentleman who’s been taking care of me

“He’s the old gentleman who’s been taking care of me.”"You mean your father?”"No, no, doctor That guy isn’t my father He just looks like him. But I don’t think he means any harm.”"Arthur, why do you think he’s an impostor? What gives you that impression?”He gave me a patient look – as if to say, how could I not see the obvious? – and said, “Yes, he looks exactly like my father but he really isn’t. He’s a nice guy, doctor, but he certainly isn’t my father.”"But why is this man pretending to be your father?”Arthur seemed sad and resigned as he said, “That is what is so surprising, doctor. Why should anyone want to pretend to be my father? Maybe my real father employed him to take care of me, paid him some money so that he could pay my bills.” Later, in my office, Arthur’s parents added another twist to the mystery. Apparently their son did not treat either of them as impostors when they spoke to him over the telephone. He only claimed they were impostors when they met face-to-face. This implied that Arthur did not have amnesia with regard to his parents and that he was not simply “crazy”.”It’s so upsetting,” Arthur’s father said.

“He recognises all sorts of people he knew in the past, including his college room-mates, his best friend from childhood and his former girlfriends He doesn’t say that any of them is an impostor. He seems to have some gripe against his mother and me.”I felt deeply sorry for Arthur’s parents. We could probe their son’s brain and try to shed light on his condition – and perhaps comfort them with a logical explanation for his curious behaviour – but there was scant hope of an effective treatment This sort of neurological condition is usually permanent. But I was pleasantly surprised one Saturday morning when Arthur’s father called me, excited about an idea he’d got from watching a television programme on phantom limbs in which I demonstrated that the brain can be tricked by simply using a mirror. “Dr Ramachandran,” he said, “if you can trick a person into thinking that his paralysed phantom limb can move again, why can’t we use a similar trick to help Arthur get rid of his delusion?”Indeed, why not? The next day, Arthur’s father entered his son’s bedroom and announced cheerfully, “Arthur, guess what! That man you’ve been living with all these days is an impostor He really isn’t your father You were right all along So I have sent him away to China. I am your real father.” He moved over to Arthur’s side and clapped him on the shoulder. “It’s good to see you, son!”Arthur blinked hard at the news but seemed to accept it.

When he came to our laboratory the next day I said, “Who’s that man who brought you in today?”"That’s my real father.”"Who was taking care of you last week?”"Oh,” said Arthur, “that guy has gone back to China. He looks similar to my father, but he’s gone now.”Alas, this intellectual acceptance of his parents did not last. One week later Arthur reverted to his original delusion, claiming that the impostor had returned.Arthur was suffering from Capgras’ delusion, one of the rarest and most colourful syndromes in neurology. The patient, who is often mentally quite lucid, comes to regard close acquaintances – usually his parents, children, spouse or siblings – as impostors. Although such bizarre delusions can crop up in psychotic states, more than a third of the documented cases of Capgras’ syndrome have occurred in conjunction with traumatic brain lesions, like the head injury that Arthur suffered This suggests to me that the syndrome has an organic basis. But the majority of Capgras’ patients are dispatched to psychiatrists, who tend to favour a Freudian explanation of the disorder.In this analysis, all of us as children are sexually attracted to our parents. Thus every male wants to make love to his mother and comes to regard his father as a sexual rival (the Oedipus complex), and every female has lifelong deep-seated sexual obsessions about her father (the Electra complex).

Although these forbidden feelings become fully repressed by adulthood, they remain dormant. Then, along comes a blow to the head (or some other release mechanism) and the repressed sexuality toward a mother or father comes flaming to the surface; as in, “I could never feel this kind of sexual jealousy toward my real father, so this man must be an impostor.” This explanation is ingenious, but then I came across a patient who had delusions similar to Arthur’s – only about his pet poodle.A better approach to studying Capgras’ syndrome requires one to take a closer look at neuroanatomy, specifically at pathways concerned with visual recognition and emotions in the brain. The temporal lobes contain regions that specialise in face and object recognition – the “what pathway”. We know this because when specific portions of the what pathway are damaged, patients lose the ability to recognise faces, even those of close friends and relatives. Normally, these face recognition areas (found on both sides of the brain) relay information to the limbic system, found deep in the middle of the brain, which then helps to generate emotional responses to particular faces.

When I look at a face, my temporal cortex recognises the image – mother, boss, friend – and passes on the information to my amygdala (a gateway to the limbic system) to discern its emotional significance – love, anger, disappointment, and so on.After thinking about Arthur’s symptoms, it occurred to me that his strange behaviour might have resulted from a disconnection between these two areas (the one concerned with recognition and the other with emotion). Maybe Arthur’s face-recognition pathway was still completely normal, and that was why he could identify everyone, including his mother and father, but the connections between this “face region” and his amygdala had been selectively damaged. If that were the case, Arthur would recognise his parents but would not experience any emotions when looking at their faces, and so would assume them impostors.Now, this is an intriguing idea, but how does one go about testing it? When you are emotionally aroused you start sweating, not only to dissipate the heat building up in your muscles but to give your sweaty palms a better grip on a tree branch, a weapon or an enemy’s throat. From the experimenter’s point of view, your sweaty palms are the most important aspect of your emotional response to the face. The dampness of your hands is a sure giveaway of how you feel toward that person. Moreover, we can measure this reaction very easily by placing electrodes on your palm and recording changes in the electrical resistance of your skin.