Now Capgras and Cotard are both rare syndromes. But there's another disorder, a sort of mini-Cotard's that's much more commonly seen in clinical practice (those of you here who are psychiatrists know this, or psychologists). It's called Derealisation and Depersonalisation. It's seen in acute anxiety, panic attacks, depression and other dissociative states. Suddenly the world seems completely unreal - like a dream. Or you may feel that you are not real - Doctor, I feel like a zombie. Why does this happen? As I said, it's quite common.
I think it involves the same circuits as Capgras and Cotard's. You've all heard of the phrase, playing possum. An opossum when chased by a predator suddenly loses all muscle tone and plays dead. Why? This is because any movement by the possum will encourage the predatory behaviour of the carnivore - and carnivores also avoid dead infected food. So playing dead is very adaptive for the possum.
Following the lead of Martin Roth and Sierra and Berrios, I suggested Derealisation and Depersonalisation and other dissociative states are an example of playing possum in the emotional realm. And I'll explain. It's an evolutionary adaptive mechanism. Remember the story of Livingstone being mauled by a lion.
Dr. Livingston, (picture courtesy of John Murray, Publishers)
He saw his arm being ripped off but felt no pain or even fear. He felt like he was detached from it all, watching it all happen. The same thing happens, by the way, to soldiers in battle or sometimes even to women being raped. During such dire emergencies, the anterior cingular in the brain, part of the frontal lobes, becomes extremely active. This inhibits or temporarily shuts down your amygdala and other limbic emotional centres, so you suppress potentially disabling emotions like anxiety and fear - temporarily. But at the same time, the anterior cingular makes you extremely alert and vigilant so you can take the appropriate action.
Now of course in an emergency this combination of shutting down emotions and being hyper-vigilant at the same time is useful, keeping you out of harm's way. It's best to do nothing than engage in some sort of erratic behaviour. But what if the same mechanism is accidentally triggered by chemical imbalances or brain disease, when there is no emergency. You look at the world, you're intensely alert, hyper-vigilant, but it's completely devoid of emotional meaning because you've shut down your limbic system. And there are only two ways for you to interpret this dilemma. Either you say the world isn't real - and that's called Derealisation. Or you say, I'm not real, I feel empty - and that's called Depersonalisation.
Epileptic seizures originating in this part of the brain can also produce these dreamy states of Deralisation and Depersonalisation. And, intriguingly, we know that during the actual seizure when the patient is experiencing Derealisation, you can obtain a Galvanic Skin Response and there's no response to anything. But once he comes out of the seizure, fine, he's normal. And all of this supports the hypothesis that I'm proposing.
OK, finally let's talk about another disorder, the one that jumps into people's minds when they think of madness - namely schizophrenia. These are patients who have bizarre symptoms. They hallucinate, often hearing voices. They become delusional, thinking they're Napoleon - or George Bush. Or they're convinced the CIA has planted devices in their brain to control their thoughts and actions. Or that aliens are controlling them.
Psycho-pharmacology has revolutionised our ability to treat schizophrenia, but the question remains: why do they behave the way they do? I'd like to speculate on this based on some work we've done on anosognosia (denial of illness) - which you see in right-hemisphere lesions - and some very clever speculations by Chris Frith and Sarah Blakemore. Their idea is that unlike normal people, the schizophrenic can't tell the difference between his own internally-generated images and thoughts versus perceptions that are evoked by real things outside.
If anyone of you here conjures up a mental picture of a clown in front of you, you don't confuse it with reality partly because your brain has access to the internal command you gave. You're expecting to visualise a clown, that's why you see it and you don't hallucinate. But if the mechanism in your brain that does this becomes faulty, then all of a sudden you can't tell the difference between a clown you're imagining and a clown you're actually seeing there. In other words, you hallucinate. You can't tell the difference between fantasy and reality.
Similarly, you and I momentarily entertain the thought it would be nice to be Napoleon. But in a schizophrenic this momentary thought becomes a full-blown delusion instead of being vetoed by reality.
What about the other symptoms of schizophrenia - the fact that aliens are controlling you? When you move your finger voluntarily, you know you sent the command, the motor centres in the brain sent the command. So you experience willing the movement. You don't say, Oh the finger moved on its own. But if the mechanism that performs this comparison is flawed, you no longer experience YOU willing the movement. So you come up with this bizarre interpretation. You say your movements are controlled by aliens or brain implants - and of course that's what paranoid schizophrenics do. How do you test a theory like this?
I want you all now to try an experiment. I mean that. I want you to try an experiment on yourselves. Using your right index finger - all of you try it - tap repeatedly your left index finger, keeping your left index finger steady and inactive. So you're all tapping your left index finger using your right index finger - left index finger is perfectly steady. Now you'll feel the tapping only on the left finger, very little on the right finger. OK, how many of you feel that? Yes, raise your hands. OK, 99 per cent of you. There are a few mutants, but we won't pursue that.
Now why is that? That's because the brain has sent a command from the left hemisphere to the right hand saying, Move. So the brain knows, it's tipped off the sensory areas of the brain, saying, Look you're going to move your right finger up and down so it's going to get some touch signals. But ignore them. It's not important. On the other hand, the left hand is perfectly steady so you feel the sensation only on the left finger, even though the tactile input is exactly the same.
Now try it the other way. Hold the right finger steady. Tap with the left finger. And you should now feel it mostly on the right, not on the left. Now the prediction is, if a schizophrenic tries this experiment, since he does not know the difference between internally generated actions and externally generated sensory stimuli, he will feel the sensations equally in both the fingers. It's a five- minute experiment - nobody's ever tried it.
Another prediction. I can come here and tickle anyone of you and you start laughing. Now interestingly, you can't tickle yourself. Try as hard as you want, you cannot tickle yourself. That's because your brain knows you're sending the command. Prediction: a schizophrenic should be able to tickle himself.
OK, it's time to conclude now. I hope that I've convinced you that even though the behaviour of many patients with mental illness seems bizarre, we can now begin to make sense of the symptoms using our knowledge of basic brain mechanisms. You can think of mental illness as disturbances of consciousness and of self, two words that conceal depths of ignorance. Let me try to summarise in the remaining five or ten minutes what my own view of consciousness is. There are really two problems here - the problem of the subjective sensations or qualia (а
The question is how does the flux of ions in little bits of jelly in my brain give rise to the redness of red, the flavour of marmite or mattar paneer, or wine. Matter and mind seem so utterly unlike each other. Well one way out of this dilemma is to think of them really as two different ways of describing the world, each of which is complete in itself. Just as we can describe light as made up of particles or waves - and there's no point in asking which is correct, because they're both correct and yet utterly unlike each other. And the same may be true of mental events and physical events in the brain.
But what about the self? The last remaining great mystery in science, it's something that everybody's interested in - and especially if you're from India, like me. Now obviously self and qualia are two sides of the same coin. You can't have free-floating sensations or qualia with no-one to experience it and you can't have a self completely devoid of sensory experiences, memories or emotions. For example as we saw in Cotard's syndrome, sensations and perceptions lose all their significance and meaning - and this leads to a dissolution of self.
What exactly do people mean when they speak of the self? Its defining characteristics are fourfold. First of all, continuity. You've a sense of time, a sense of past, a sense of future. There seems to be a thread running through your personality, through your mind. Second, closely related is the idea of unity or coherence of self. In spite of the diversity of sensory experiences, memories, beliefs and thoughts, you experience yourself as one person, as a unity.
So there's continuity, there's unity. And then there's the sense of embodiment or ownership - yourself as anchored to your body. And fourth is a sense of agency, what we call free will, your sense of being in charge of your own destiny. I moved my finger.
Now as we've seen in my lectures so far, these different aspects of self can be differentially disturbed in brain disease, which leads me to believe that the self really isn't one thing, but many. Just like love or happiness, we have one word but it's actually lumping together many different phenomena. For example, if I stimulate your right parietal cortex with an electrode (you're conscious and awake) you will momentarily feel that you are floating near the ceiling watching your own body down below. You have an out-of-the-body experience. The embodiment of self is abandoned. One of the axiomatic foundations of your Self is temporarily abandoned. And this is true of each of those aspects of self I was talking about. They can be selectively affected in brain disease.
Keeping this in mind, I see three ways in which the problem of self might be tackled by neuroscience. First, maybe the problem of self is a straightforward empirical problem. Maybe there is a single, very elegant, Pythagorean Aha! solution to the problem, just like DNA base-pairing was a solution to the riddle of heredity. I think this is unlikely, but I could be wrong.
Second, given my earlier remarks about the self, the notion of the self as being defined by a set of attributes - embodiment, agency, unity, continuity - maybe we will succeed in explaining each of these attributes individually in terms of what's going on in the brain. Then the problem of what is the self will vanish or recede into the background.
Third, maybe the solution to the problem of the self won't be a straightforward empirical one. It may instead require a radical shift in perspective, the sort of thing that Einstein did when he rejected the assumption that things can move at arbitrarily high velocities. When we finally achieve such a shift in perspective, we may be in for a big surprise and find that the answer was staring at us all along. I don't want to sound like a New Age guru, but there are curious parallels between this idea and the Hindu philosophical view that there is no essential difference between self and others or that the self is an illusion.
Now I have no clue what the solution to the problem of self is, what the shift in perspective might be. If I did I would dash off a paper to Nature today, and overnight I'd be the most famous scientist alive. But just for fun let me have a crack at it, at what the solution might look like.
Our brains were essentially model-making machines. We need to construct useful, virtual reality simulations of the world that we can act on. Within the simulation, we need also to construct models of other people's minds because we're intensely social creatures, us primates. We need to do this so we can predict their behaviour. We are, after all, the Machiavellian primate. For example, you want to know was what he did a wilful action. In that case he might repeat it. Or was it involuntary in which case it's quite benign. Indeed evolution may have given us the skill even before self- awareness emerged in the brain. But then once this mechanism is in place, you can also apply it to the particular creature who happens to occupy this particular body, called Ramachandran.
At a very rudimentary level this is what happens each time a new-born baby mimics your behaviour. Stick your tongue out next time you see a new-born-baby and the baby will stick its tongue out, mimicking your behaviour, instantly dissolving the boundary, the arbitrary barrier between self and others. And we even know that this is carried out by a specific group of neurons in the brain, in your frontal lobes, called the mirror neurons. The bonus from this might be self-awareness.
With this I'd like to conclude this whole series of lectures. As I said in my first lecture, my goal was not to give you a complete survey of our knowledge of the brain. That would take fifty hours, not five. But I hope I've succeeded in conveying to you the sense of excitement that my colleagues and I experience each time we try to tackle one of these problems, whether you're talking about hysteria, phantom limbs, free will, the meaning of art, denial, or neglect or any one of these syndromes which we talked about in earlier lectures. Second, I hope I've convinced you that by studying these strange cases and asking the right questions, we neuroscientists can begin to answer some of those lofty questions that thinking people have been preoccupied with since the dawn of history. What is free will? What is body image? What is the self? Who am I? - questions that until recently were the province of philosophy.
No enterprise is more vital for the wellbeing and survival of the human race. This is just as true now as it was in the past. Remember that politics, colonialism, imperialism and war also originate in the human brain.
Thank you.
