The main theme of our lectures so far has been the idea that
the study of patients with neurological disorders has implications
far beyond the confines of medical neurology, implications even for
the humanities, for philosophy, maybe even for aesthetics and art.
Today I'd like to continue this theme and take up the challenge of
mental illness. The boundary between neurology and psychiatry is becoming
increasingly blurred and it's only a matter of time before psychiatry
becomes just another branch of neurology. I'll also touch on a few
philosophical issues like free will and the nature of self.
Now if you look at ideas on mental illness, there've been traditionally
two different approaches to mental illness. The first one tries to
identify chemical imbalances, changes in transmitters and receptors
in the brain - and attempts to correct these changes using drugs.
And this approach has revolutionised psychiatry. It's been phenomenally
successful. Patients who used to be put in straight jackets or locked
up can now lead relatively normal lives. The second approach we can
loosely characterise as the so-called Freudian approach. It assumes
that most mental illness arises from your upbringing - maybe your
mother. In this lecture what I'd like to do is propose a third approach
which is radically different from either of these but in a sense complements
them.
My point is if you really want to understand the origins of mental
illness it's not enough to merely say that some transmitter has changed
in the brain. You want to know how the change in the transmitter produces
the bizarre symptoms that it does - why patients have those specific
symptoms which you see and why the symptoms are different for different
types of mental illness. That's our agenda here. And what I'd like
to do is to try and explain the symptoms you see in mental illness
in terms of the known function and the known anatomy and neural structures
in the brain. And that will be the goal of this lecture. And I'll
suggest that many of these symptoms and disorders will seem less bizarre
when viewed from an evolutionary standpoint, that is from a Darwinian
perspective. So let's give this discipline a new name - and I'd like
to call this discipline evolutionary neuro-psychiatry.
Let's take the classic example of what people think of as a purely
mental disorder, psychological disturbance - hysteria. Now I'm using
the word here in the strictly medical sense, not somebody becoming
hysterical and shouting and screaming. In the strictly medical sense,
the word means that here is a patient who suddenly develops a paralysis
of an arm or a leg, but if you examine this patient neurologically
there are no deficits, brain MR scan reveals that the brain is apparently
completely normal, there are no identifiable lesions, there's no damage.
So the symptoms are dismissed as being purely psychological in origin.
But recent brain-imaging studies using PET scans and functional Magnetic
Resonance imaging have dramatically changed our understanding of hysteria.
Using PET scans and NMR, we can now find what parts of the brain are
active or inactive, for example when a patient does some specific
action or some mental process. And you can find out what parts of
the brain light up when he does it - for example when you do arithmetic,
mental arithmetic, what part of the brain lights up? (It's usually
the left angular gyrus, it turns out). Or when I prick you with a
needle and there's pain, what part of the brain lights up, what are
the pathways involved? And this tells you that that particular pathway
that's lighting up is somehow involved in mediating that function.
If I take anyone of you here and ask you to wiggle your finger and
I do a PET scan to see what parts of the brain light up (and Kornhuber
and Libet actually did this some decades ago) what I find is that
two areas light up in the brain. One is called the motor cortex, which
is actually sending messages to execute the appropriate sequence of
muscle twitches to wiggle your finger. But also another area in front
of it called the pre-frontal cortex that prepares you to move your
finger. So there's an initial area which prepares you to move your
finger and then there's the motor cortex that executes the motor programmes
to make you wiggle your finger.
OK, fine. But what if you now try this experiment on an hysterical
patient, who's hysterically paralysed? He says his arm isn't moving
but there are no neurological abnormalities. What if you did a PET
scan in his brain and you asked him to move his so-called paralysed
arm. He says, No I can't do it. You say, Try anyway - and do a PET
scan. And this was done by Chris Frith and Frackowiak and Peter Halligan
and John Marshall and others. And what they found was when a person
with hysterical paralysis tries to move his arm, again the pre-motor
area lights up. And this means he's not faking it. He's intending
to move the arm. But in addition to that there's another area that
lights up. And that is the anterior cingular and the ventromedial
frontal lobes, parts of the frontal cortex. This means he has every
intention of moving it, but the anterior cingular and parts of the
frontal lobes are inhibiting or vetoing this attempt to move the arm
in the hysterical patient. And this makes sense because the anterior
cingular and parts of the frontal lobes are intimately linked to the
limbic emotional centres in the brain. And we know that hysteria originates
from some emotional trauma that's somehow preventing him from moving
his arm - and his arm is paralysed.
So we've talked about hysterical patients with hysterical paralysis.
Now let's go back to normals and do a PET scan when you're voluntarily
moving your finger using your free will. A second to three-fourths
of a second prior to moving your finger, I get the EEG potential and
it's called the Readiness Potential. It's as though the brain events
are kicking in a second prior to your actual finger movement, even
though your conscious intention of moving the finger coincides almost
exactly with the wiggle of the finger. Why? Why is the mental sensation
of willing the finger delayed by a second, coming a second after the
brain events kick in as monitored by the EEG? What might the evolutionary
rationale be?
The answer is, I think, that there is an inevitable neural delay before
the signal arising in the brain cascades through the brain and the
message arrives to wiggle you finger. There's going to be a delay
because of neural processing - just like the satellite interviews
on TV which you've all been watching. So natural selection has ensured
that the subjective sensation of wiling is delayed deliberately to
coincide not with the onset of the brain commands but with the actual
execution of the command by your finger, so that you feel you're moving
it.
And this in turn is telling you something important. It's telling
you that the subjective sensations that accompany brain events must
have an evolutionary purpose, for if it had no purpose and merely
accompanied brain events - like so many philosophers believe (this
is called epiphenomenalism) - in other words the subjective sensation
of willing is like a shadow that moves with you as you walk but is
not causal in making you move, if that's correct then why would evolution
bother delaying the signal so that it coincides with your finger movement?
So you see the amazing paradox is that on the one hand the experiment
shows that free will is illusory, right? It can't be causing the brain
events because the events kick in a second earlier. But on the other
hand it has to have some function because if it didn't have a function,
why would evolution bother delaying it? But if it does have a function,
what could it be other than moving the finger? So maybe our very notion
of causation requires a radical revision here as happened in quantum
physics. OK, enough of free will. It's all philosophy!
I'd now like to remind you of a syndrome we discussed in my first
lecture, the Capgras
delusion. So, the patient has been in a head injury,
say a car accident. He seems quite normal in most respects, neurologically
intact, but suddenly starts saying his mother is an impostor. She's
some other woman pretending to be my mother. Now why would this happen,
especially after a head injury? Now remember, he's quite normal in
all other respects.
Well, it turns out in this patient the wire that goes from the visual
areas to the emotional core of the brain, the limbic system and the
amygdala,
that's been cut by the accident. So he looks at the mother and since
the visual areas in the brain concerned with recognising faces is
not damaged, he says, Hey it looks just like my mother. But then there
is no emotion because that wire taking that information to the emotional
centres is cut. So he says, If this is my mother how come I don't
experience any emotions? This must be some other strange woman. She's
an impostor. Well, how do you test this?
It turns out you can measure the gut-level emotional reaction that
someone has to a visual stimulus - or any stimulus - by measuring
the extent to which they sweat. Believe it or not, all of you here
- if I show you something exciting, emotionally important, you start
sweating to dissipate the heat that you're going to generate from
exercise, from action. And I can measure the sweating by putting two
electrodes in your skin, changes in skin resistance - and if skin
resistance falls, this is called the Galvanic Skin Response. So every
time anyone of you here looks at tables and chairs, there's no Galvanic
Skin Response because you don't get emotionally aroused if you look
at a table or a chair. If you look at strangers there's no Galvanic
Skin Response. But if you look at lions and tigers and - as it turns
out - if you look at your mother, you get a huge, big Galvanic Skin
Response. And you don't have to be Jewish, either. Anybody here, looking
at your mother, you get a huge, big Galvanic Skin Response when you
look at your mother.
Well, what happens to the patient? We've tried this on patients. The
patient looks at chairs and tables, nothing happens. But then we show
him a picture of his mother on the screen, no Galvanic Skin Response.
It's flat - supporting our idea that there's been a disconnection
between vision and emotion.
Now the Capgras delusion is bizarre enough, but I'll tell you about
an even more bizarre disorder. This is called the Cotard's
syndrome, in which the patient starts claiming he is
dead. I suggested that this is a bit like Capgras except that instead
of vision alone being disconnected from the emotional centres in the
brain, all the senses, everything, gets disconnected from the emotional
centres. So that nothing he looks at in the world makes any sense,
has any emotional significance to this person, whether he sees it
or touches it or looks at it. Nothing has any emotional impact. And
the only way this patient can interpret this complete emotional desolation
is to say, Oh, I'm dead, doctor. However bizarre it seems to you,
it's the only interpretation that makes sense to him.
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
and the problem of the self. The problem of qualia
is the more difficult one.
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.
