To better tell you about this incredible story, I shall first give you a brief smattering on how what we see through our eyes is then processed inside of our brain. When an image (rays of light) hits our retina, a visual signal is converted into an electrical signal and sent inside of our brain. The mental elaboration of an image is an extremely complex mechanism, and it is just crazy to think how fast and efficient this process is and how we do not consciously realize what happened in between the visual signal and its final output. In very simple words: visual data are sent to a cerebral structure, the fusiform gyrus in which objects, faces and places are subject to a primary evaluation. At this hub, the acquired visual data are subdivided through 4 main paths: the one which interests us most is the way number 3 that gets to the Amygdala.
The amygdala is an extremely fascinating structure! It is the perception center of our emotions, and differently from long-held beliefs, it is tightly connected with the superior centers of our Reason. Indeed, as already established by other neuroscience and social behavior studies, emotions and reason are inseparable. Thanks to our amygdala and its widespread connections, we are able to “emotionally load” everything we see. If we would see a lion, definitely our amygdala would “kindly” suggest us to flee. In doing so it would communicate to our reasoning superior centers to prepare ourselves to flee, and to our inferior centers, such as the hypothalamus, to secrete all the needed neuro-transmitters and hormones to fuel our body in order to run away as quickly as possible.
After this short trip into our mind (far from being exhaustive), we can proceed with David’s history.David is an American lad, which had a terrible car crash. He spent in a coma around two weeks, but luckily he woke up and in a few months he was back to normal life. David was able to reading and writing, he was attentive, however, suffered from a really grave malaise. When he was meeting his mom he was uttering: “Doctor, this woman is identical to my mom, but she isn’t her: she’s an identical-looking impostor!”.
David had the same hallucination toward his father, but not for the other people. This odd pathology is called “Capgras syndrome” after the doctor that primarily described it. Heated debates are still ongoing in the scientific community to shed light regarding the causes beneath this pathology; indeed, many doctors believed that patients were just deceiving them. They argued “why this should happen only with their mom and not with other people?”.
A doctor from the University of California, Vilayanur Ramachandran, solved this case thanks to brilliant insights followed by even more brilliant confirmatory experiments. Dr. Ramachandran hypothesized that in David, the neuronal way bringing the visual signal from the fusiform gyrus to the amygdala had been damaged. Thus, David was still perfectly able to recognize his mother’s face but he could not associate the usual “emotional load” onto it. In other words, he recognized a familiar face, but lacked the emotional “glow” that such a face would normally evoke. During these kind of situations, our brain tends to extremely rationalize every mental process: so extreme they may look absurd and coming out from a plot of a conspiracy movie. That’s why David believed his mother was an impostor.
But how did Dr. Ramachandran confirm his theory with substantial evidence?
As I told you before, the amygdala does not only communicate with the “superior centers” of our brain but also with lower ones. This is because its role is to prepare not only our mind, but also our body to react to external stimuli. Hence, our body reacts to amygdala-directed stimuli with a different intensity, depending on the strength of the initial visual input (in our case). One of the best-characterized reaction coming from the amygdala is the change in the skin conductance: our skin gets damper at increasing level of emotional excitement. Skin conductance can be experimentally measured via an ohmmeter; which controls skin electrical conductance in real time. In this way, we can exactly know whether, in a given moment, there is a change in our skin conductance that can be related directly to a change in our emotional state. Just to give you an idea of the reliability of this system; the ohmmeter is one of the most important components of the truth machine.
Well, all of us will have an increased skin conductance when faced with a picture of our mom. We just cannot avoid this, all moms, and not only the “Italian mamma”, will generate a huge emotional response of our body. Nevertheless, as predicted by Dr. Ramachandran, David did not have any emotional answer since the one in the picture was just an impostor and not his real mom. To make things even more weird, when David was talking at the phone with his mom he was just fine; indeed, he recognized her and had normal conversations. This is because the amygdala is connected with our auditory system through a different way, not damaged by the accident. It follows that her voice was still able to generate all those peculiar positive emotions associated with our mom’s mental image.
We can now finally answer to the initial questions: “why David was not able to recognize his mother, but instead he could recognize other people he knew before?”. In our cerebral world, mom is life. She is the first thing we see, the first we remember, she is our first emotion, the first discovery we make! Her face is so hard-wired in our emotional centers that there is no way to look at her without feeling an amazing whirlwind of emotions. This does not happen with other people, however, in other cases the Capgras syndrome does not show up like this. For example, people who always felt deep emotions while looking at beautiful views or landscapes, were not able anymore to feel the same; they just remained cold while facing everything that was used to move their souls in the past.
And now, Dr. Ramachandran tells a last funny anecdote about this syndrome in his famous book “The Tell-tale brain”. A lawyer called Dr. Ramachandran because a client of him claimed he was not able to recognize anymore his wife after a car accident. The jury did not believe this story, therefore, the lawyer asked for the scientist’s help to prove his client was sincere. Unfortunately, our story has no happy ending. Indeed, Dr. Ramachandran affirmed that, differently from what happens when you see your mom, there could be no test about a “wife-recognition”. In fact, if connected to an ohmmeter, he would definitely have an increased skin conductance as he would see a “stranger” looking like his wife! Despite “the flames of the passion” can decrease in time, overwhelmed by the marriage routines, the features that made us choose our half would activate the amygdala even when coming from a stranger.
Ah, if we could generate a bit of Capgras syndrome in married couples broken by the burden of the years and monotony!
We could make a lot of money!