The Tell-Tale Brain: A Neuroscientist's Quest for What Makes Us Human

“I don’t know what you’re saying. You know the world is illusory as the Hindus say. Its all maya [the Sanskrit word for “illusion”]. And if the world doesn’t exist, then in what sense do I exist? We take all that for granted, but it simply isn’t true.”

“Ali, what are you saying? Are you saying you may not exist? How do you explain that you are here talking to me right now?”

Ali appeared confused and a tear started forming in his eye. “Well, I am dead and immortal at the same time.”

In Ali’s mind—as in the minds of many otherwise “normal” mystics—there is no essential contradiction in his statement. I sometimes wonder whether such patients who have temporal lobe epilepsy have access to another dimension of reality, a wormhole of sorts into a parallel universe. But I usually don’t say this to my colleagues, lest they doubt my sanity.

Ali had one of the strangest disorders in neuropsychiatry: Cotard syndrome. It would be all too easy to jump to the conclusion that Ali’s delusion was the result of extreme depression. Depression very often accompanies Cotard syndrome. However, depression alone cannot be the cause of it. On the one hand, less extreme forms of depersonalization—in which the patient feels like an “empty shell” but, unlike a Cotard patient, retains insight into his illness—can occur in the complete absence of depression. Conversely, most patients who are severely depressed don’t go around claiming they are dead. So something else must be going on in Cotard syndrome.

Dr. Santhanam started Ali on a regimen of the anticonvulsant drug lamotrigine.

“This should help you get better,” he said. “We are going to start you on a small dose because in a few rare cases patients develop a very severe allergic skin rash. If you develop such a rash, stop the medicine immediately and come and see us.”

Over the next few months Ali’s seizures disappeared, and as an added bonus his mood swings diminished and he became less depressed. Yet even three years later he continued to maintain that he was dead.¹⁴

What would be causing this Kafkaesque disorder? As I noted earlier, pathways 1 (including parts of the inferior parietal lobule) and 3 are both rich in mirror neurons. The former is involved in inferring intentions and the latter, in concert with the insula, is involved in emotional empathy. You have also seen how mirror neurons might not only be involved in modeling other people’s behavior—the conventional view—but may also turn “inward” to inspect your own mental states. This could enrich introspection and self-awareness.

The explanation I propose is to think of Cotard syndrome as an extreme and more general form of Capgras syndrome. People with Cotard syndrome often lose interest in viewing art and listening to music, presumably because such stimuli also fail to evoke emotions. This is what we might expect if all or most sensory pathways to the amygdala are totally severed (as opposed to Capgras syndrome, in which just the “face” area in the fusiform gyrus is disconnected from the amygdala). Thus for a Cotard patient, the entire sensory world, not just Mum and Dad, would seem derealized—unreal, as in a dream. If you added to this cocktail a derangement of reciprocal connections between the mirror neurons and the frontal lobe system, you would lose your sense of self as well. Lose yourself and lose the world—that’s as close to death in life as you can get. No wonder severe depression frequently, though not always, accompanies Cotard syndrome.

Note that in this framework it is easy to see how a less extreme form of Cotard syndrome could underlie the peculiar states of derealization (“The world looks unreal as in a dream”) and depersonalization (“I don’t feel real”) that are frequently seen in clinical depression. If depressed patients have selective damage to the circuits that mediate empathy and the salience of external objects, but intact circuitry for self-representation, the result could be derealization and a feeling of alienation from the world. Conversely, if self-representation is mainly affected, with normal reactions to the outside world and people, the sense of internal hollowness or emptiness that characterizes depersonalization would be the result. In short, the feeling of unreality is attributed to either oneself or the world depending on differential damage to these closely linked functions.

The extreme sensory-emotional disconnection and diminishment of self I am proposing as an explanation for Cotard syndrome would also explain such patients’ curious indifference to pain. They feel pain as a sensation but, like Mikhey (whom we met in Chapter 1), there is no agony. As a desperate attempt to restore the ability to feel something—anything!—such patients may try to inflict pain on themselves in order to feel more “anchored” in their bodies.