We have all had the experience of forgetting a person's name and only remembering their face. Life is a hectic game, and it is often hard enough remembering who your friends are without having to add acquaintances whom you have met momentarily. We are all human, after all.
What if this problem, however, was reversed? What if you could not recognize faces that were familiar to you? There are many such disorders, and all can shed some light on the functioning of the brain. But one curious disorder has proven especially useful in understanding the process of facial recognition, memory management and relating these processes to emotion. It is called Capgras syndrome, and it has the most peculiar traits.
Patients with Capgras syndrome not only fail to recognize close acquaintances, but they come to view those individuals as imposters who may look like their friends or family, but in their reality are not. Now, this happens in a lot of psychotics but it also widely occurs in otherwise perfectly normal individuals who have suffered brain lesions. Investigating this matter, therefore, can give insight on the mind's machinery.
Enter Vilayanur Ramachandran of the Brain and Perception Laboratory at the University of California, San Diego, who has used case studies and experiments on individuals to better understand what makes this curious disorder tick. Ramachandran, a well-known neurologist, has widely lectured on the issue, and at a recent Technology, Entertainment, Design conference in Monterrey, California, spoke about his first forays into understanding the disorder and what his experiments revealed.
Ramanchandran explained previous Freudian explanations for how the disorder came about. The central idea of the Freudian hypothesis would be that the man's early sexual urges towards his mother (the so-called Oedipus complex) in his earlier days were inhibited by the growth of the cortex. Should the cortex have lesions due to an accident of some sort, the rush of sexual urges moves towards the surface of the man's consciousness. When confronted by his mother and the subsequent sexual urges, the man in question refuses to recognize that he is sexually attracted to his mother, and therefore convinces himself that the individual he is looking at is an imposter and not really his mother.
Ramachandran dismissed this view as never making much sense, because he had seen the same situation between an individual and their pet dog, which would suggest a radical revision of the Freudian theory to explain the "latent bestiality" present in all human beings.
Moving on to how neurology dealt with the problem, Ramachandran explains that the visual areas of the brain which interpret signals from our eyes wire into a small area of the temporal lobe called the fusiform gyrus. This relay center of sorts then has a subsequent connection to the amygdala in the limbic system, essentially the emotional center of the brain.
In many patients with Capgras syndrome, this wire linking the visual information to the emotion center is severed. The result is that emotional feelings cannot be visual representations. An individual with Capgras, therefore, is unable to attach any emotional feeling to close acquaintances like a mother, father, or even a household pet. This results in the individual convinced that such acquaintances are imposters.
Ramachandran and his colleague William Hirstein at UCSD devised an ingenious method for testing this hypothesis. Normal human response to visual images can vary, but reactions can be measured using galvanic skin response, essentially measuring sweat response to visual images. When a person sees objects that evoke emotional responses, such as a tiger or his/her mother (no similarities assumed), they begin to sweat in reaction to these stimuli. Individuals with Capgras syndrome do not exhibit this response when they see close acquaintances, confirming the hypothesis that there is no visual signal to emotional center connection. This holds great promise for understanding how over time memory may be acquired, relayed to sensory information, and then stored in the mind.
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