The objectivity of subjective experiences

Perhaps not enough has been made of the extent to which brain imaging techniques are beginning to enrich our understanding of the brain. Most people marvel – and with good reason – at the fact that these imaging techniques demonstrate with fair certainty that specific experiences – for example of colour or of visual motion – correlate with activity in a specific area of the brain. But imaging techniques have gone way beyond and have made what was thought to be outside the realm of objective observation the target of experimental studies, and with huge success. Fear, expectation of reward, the experience of love and of beauty – all of them thought until recently to be unverifiable, or not easily verifiable, subjective experiences - have been shown to have neural correlates specific to them. Hence, to ascertain that someone is in love, I need only show them the picture of their [suspected] lover and note whether there is any activity in the brain areas that have been shown to correlate with feelings of love. In time, no doubt lawyers will be using such evidence in court proceedings.

But there is another aspect to these studies that has escaped comment although its impact may yet turn out to be as great as the demonstration that subjective feelings have distinct neural correlates. The experience of beauty provides a very good example.

In 2004, Hideaki Kawabata and I published a paper showing that the experience of beauty correlates with activity in the orbito-frontal cortex, a part of the brain that is linked to reward. In that study, we showed subjects many paintings – abstract, landscape, portraits, still lifes – and asked them to rate the paintings in terms of their beauty. Different subjects gave different ratings to the same paintings. Sometimes, a painting judged to be of high beauty by one subject was given a low rating by another. Yet whenever a subject a painting in the scanner that they rated as beautiful viewed, there was increased activity in the orbito-frontal cortex. Moreover – and this is the critical point – the increase in activity was directly related to the declared rating assigned to the painting. Hence the subjective experience could be localized and quantified.

Ours is not the only study to show that the activity in specific parts of the brain is often quantifiably related to the declared subjective experience. At least two dozen other studies have shown the same result for different subjective experiences. This, it seems to me, is a major achievement of brain imaging studies. It brings subjective experiences firmly into the realm of measurable science.

The changing brain studied through violence

I have recently read a paper that, I believe, has not received the attention it deserves, at least in the media. It is a study of the re-organiztion of the brain in response to violence. What it is that suddenly triggers a violent behaviour in some individuals is not known with any certainty, but it has long been suspected that exposure to violence leads to increased violence. We have, after all, been repeatedly told that watching violent movies results in individuals who are more readily capable of violence. But why and how?

A paper by Chris Kelly and his colleagues at Columbia Univeristy has far-reaching implications in this regard. They showed volunteer subjects clips of violent films and measured activity in different areas of the brain, using brain imaging techniques. Their results show, in brief, that repeated exposure to violence reduces the intensity of activity in a specific region of the brain known as the lateral orbito-frontal cortex progressively. The implication here is that the more violent movies are watched, the greater the reduction in orbito-frontal activity. This in itself may suggest an adaptation that makes individuals more immune to violence, adaptation being a very common occurrence in the brain. But the study goes further, to show that connections between brain areas must be in a dynamic state, and hence modifiable by experience – in this case the experience of violence – even in adult life. For the orbito-frontal cortex is connected with another brain area – the amygdala – which is known to be responsive to fearful and aggressive faces. This connection seems to be critical in the control of aggressive behaviour. The strength of connections between the two brain areas diminished progressively as violent movies were watched, and led to more aggressive tendencies. The study also strongly suggested that there developed a progressive diminished control over the initiation of violent aggressive behaviour. For there was a concomitant increase in activity within areas known to be critical in motor planning (for aggressive behaviour, among others). This suggests that the connections between the orbito-frontal cortex and yet other regions of the cortex are also in a dynamic state.

It is important to note that the study exposed subjects to violent films over relatively brief periods, each clip viewed lasting seconds rather than hours, as is common for violent movies. Hence, it does not take prolonged exposure to alter strength of connections in the brain, and in this instance, to loosen the inhibition that leads to violent aggressive behaviour.

There is a lesson in this for society, and that is why I am surprised that so little has been made of it by the media. We have discussed endlessly whether the extent of violence shown in Western movies is not damaging our already violent societies. And yet here is a study, which shows that even brief exposure can alter the balance of connections in the brain and tip them in a direction that is not socially advantageous. And there is, perhaps, a problem for legislators too. What if someone can come armed with evidence derived from brain scans to show that the crimes that he or she has committed is the result of altered brain states, induced by watching violent movies? It would be a manner of shifting responsibility. I do not know enough about law to discuss this point, but I should not be at all surprised if defence of this kind surfaces in future hearings of criminal violence cases.

But there is, above all, a great deal of interest in learning that such complex behaviour is held in check by a fine system of balance through the interactions between brain areas and that this balance is so vulnerable – even over very brief periods and even in adult life – to environmental influences. There is much in this work that is of interest for future studies in the neurobiology of aggressive behaviour and violence.

Tristan und Isolde at the Met…..

It has now been established that there is an area in the visual brain that is specialized for registering human bodies or, to put it differently, that is active when we perceive bodies. This should not come as a surprise. The brain has devoted special areas to many features that are important to us, and human bodies are very, very important. Bodies do, after all, give us a lot of information about the psychological state of a person at any given moment; we can communicate much through our body language. And the brain seems to have developed a marvellous system for recognizing at a glance, through the perceived body language, whether one a person is arrogant or diffident, proud or humble, and much else besides. Which brings me to the Metropolitan opera’s recent production of Tristan und Isolde.

To convey visually all that there is in Tristan requires an artistic and dramatic flair that is evident not only in the motion of the singers on stage but also in their inaction, the postures they adopt in the still moments. From this point of view, the Met’s recent and ill-fated production was a disappointment, or at least partially so. The staging was visually stunning in its simplicity and very effective in its use of colour. It descended once into kitsch, when Tritsan and Isolde, having swallowed the love potion and realised their profound love for one another, the lighting turned to red, eliciting laughter from the audience (something which I have not experienced before) and distracting attention from the accompanying music. Both lead singers fell ill and did not appear together except for the final performance. Illnesses prior to or during performances are bound, I imagine, to have a severe negative effect on such demanding singing and acting roles. In the performance that I attended on March 25^th, Deborah Voigt had cancelled out owing to her illness and was replaced by Janice Beard. It must be a nightmare to be forced into such a role at relatively short notice and I don’t think that she managed to pull it off. Tristan is a dignified hero, burning with a love so intense that he knows, and is resigned to, the fact that he cannot achieve it on earth. The love potion that he drank in the first Act made him inherit “eternal torment”, he laments in the last act. Ben Heppner, recovering from an illness, was not physionomically up to the role of Tristan on that particular evening. His body language simply did not convey what I believe the music intends him to convey. There was however one glorious moment, and it occurred at the end of Act 2, when King Marke sings his sad and beautiful lament: “Mir dies? Dies, Tristan, mir?” What was deeply impressive in this particular performance, apart from the splendid singing of Matti Salminen as King Marke, was the highly effective way in which body language communicated the psychological state of the protagonists – both Tristan and Isolde. They managed to communicate, through the immobile postures they adopted, as effectively as the music that feeling of unrepentant guilt, forced on them by factors beyond the control of either. It made me wonder about the neural mechanisms that underlie our ability to perceive so much in body language, even when still. Is this result of activity in the cortical area in which activity correlates with the presence of bodies? If so, then this area must be doing a great deal more than just registering the presence of bodies? Or is the activity in that area relayed, or perhaps influenced, by some other cortical area? To have felt what I felt during those moments, I assume that there is some connection with the emotional brain. Interesting questions for future study. At any rate, this one moment was worth crossing the Atlantic to see. Incidentally, I tried to see the live broadcast in London, where it was relayed to many theatres. Guess what, they were all sold out! Now on to Barcelona, for Robert Carsen’s extraordinarily rich – I speak from a neuroesthetic point of view, of course – production of Tannhäuser, last seen at the Bastille in Paris and about which I will blog in the future.

….. and neuroscience at the Italian Academy at Columbia

What were neuroscientists doing giving talks about the brain and its operations at the Italian Academy (www.italianacademy.columbia.edu), an institution supposedly devoted to Italian studies? And why did they have a full house, with many coming from the humanities? Well, the Director of the Academy, David Freedberg, is a wise man. He was among the first to embrace the field of neuroesthetics and understands that the humanities have much to offer to future studies of the brain, and that neuroscience in turn can help illuminate interesting and important problems in the humanities. The example I give above from Tristan is one among many. And the full house at the meeting he organized is testament to the fact that there are many who share this interest. All honour to David, to Anna Ipata, and to the excellent speakers at the meeting.

The sex life of voles - and the law

Voles are rodents who have a sex life which may be of considerable interest in understanding some expects of human sexuality and in reflecting on some aspects of the law relating to it.

In brief, there are two varieties of vole – the prairie and the montane voles. They differ from each other significantly with respect to their taste for monogamous and polygamous relationships. They have been studied by Larry Young and Thomas Insel in the United States. By and large, prairie voles lead a largely monogamous existence, with apparently the occasional fling. By contrast, montane voles are promiscuous and polygamous. What is it that differentiates these two varieties? Is it morality, or what may pass for morality in the world of vole ideas? (We would, or at least some would, perhaps refer to polygamous humans as immoral). Is it their up-bringing, or is it their biological constitution?

As you might have guessed, the latter seems to be the causative factor and has been traced to two neuro-hormones called oxytocin and vasopressin. These neuro-hormones have many effects but most relevant here is that they are involved in bonding between individuals and are effective in learning and memory in a social context. They are released in the reward centres of the brain when voles (and humans) have sex, which becomes therefore a rewarding experience with the chosen partner. If release of the two hormones is blocked in prairie voles, they too become promiscuous. If, on the other hand, they are injected with these hormones but prevented from having sex, they continue to be faithful to their partners, that is to have a monogamous but chaste relationship. On the other hand, injecting montane voles with these neurohormones does not make of them monogamous creatures, for the simple reason that they do not have sufficient receptors in their brains for them.

There is no evidence that these two neurohormones act in exactly the same way in humans. It would indeed be surprising if they did, given the infinitely more complex structure of the human brain and of human behaviour. But there is good reason to suppose that what applies in these animals also applies, at least in some form, in humans. And humans too can be categorized as being strictly monogamous (or serially monogamous) at one end and promiscuous to varying extents at the other. It would be highly interesting to learn whether (mainly) monogamous humans have higher concentrations of oxytocin and vasopressin, and a richer concentration of receptors for them in the reward centres of the brain, compared to more promiscuous humans. It may be that humans can be divided into several categories – ranging from the strictly monogamous to the extremely promiscuous - depending upon these concentrations. We might even find that there is a straightforward, linear, relationship between the concentration of these neuro-hormones and the incidence of promiscuity.

Which brings me to the law. No doubt the law of divorce regarding promiscuity and adultery has been much liberalised in Western countries. I do not know how the law apportions blame or arranges settlements in these instances. But the demonstration raises, it seems to me, broader issues that are relevant to the law and to how it may be modified through legislation in the future, in light of scientific findings like the one described briefly above, and others like them. For if individuals can demonstrate scientifically that their conduct, however much disapproved of by society and prohibited by law, is the consequence of their biological constitution, then the law would probably ultimately have to take account of that, as indeed it already does in certain instances. It will have to address the thorny question of the balance between biological imperatives and social prohibition. I therefore see a broadening of interest among legal legislators and the judiciary in neurobiological studies that relate to complex human conduct which comes within the province of the law. It is for this reason that, when Editor, I initiated a special issue of the Philosophical Transactions of the Royal Society on the theme of Law and the Brain. It was perhaps but a small step in a debate which, I am certain, will become increasingly important in the future.

The colour vision of the blind

In my book, A Vision of the Brain, I described a strange syndrome which I named phantom chromatopsia. In all, I have seen four patients suffering from it and have studied two in detail. The syndrome is one in which blind people see colours, usually purple or golden. The colour spreads and fills their entire “field of view”. But they take no pleasure in the sensation. The experience plunges them into a state of deep depression. One patient told me that he often felt suicidal during the chromatopsic episodes.

I accounted for the syndrome by reference to the known organization of the human visual brain. Of the many areas that constitute the visual brain, one – the V4 complex – seemed especially interesting in this context. Described by us many years ago, it is specialized for colour perception and total damage to it leads to the inability to see the world in colour – the syndrome of acquired cerebral achromatopsia. I accounted for phantom chromatopsia by supposing that an abnormal pattern of cellular activity restricted to the V4 complex results in the generation of a colour percept in the absence of an external, coloured, stimulus. The abnormality of the percept – large uniform areas of purple or gold – could be accounted for by the abnormal nature of the internally generated pattern of cellular activity compared to the normal one generated by a coloured object in the field of view.

A very interesting recent result obtained by Dr. Beauchamp and his colleagues at the University of Texas takes this a step further. They found that when they stimulated part of the colour centre through electrodes embedded in the area, the patient reported seeing colours which were not there. And what was the colour? bluish purple!

Still, the correspondence between these new results and the clinical syndrome is not complete, nor would one expect it to be, given that a pathological irritation in the V4 complex is different from a controlled stimulation of only a part of this area. The coloured area projected to the field of view in this new study is limited, whereas the colour invades the whole field of view in the pathological state. Moreover, the subjective colour produced by electrical stimulation was always purple-blue. The authors account for this by supposing that their electrode was stimulating a group of cells specialized for blue – a reasonable interpretation in light of the fact that cells constructing particular colours seem to be grouped together in the V4 complex.

But the main interest of the finding lies in showing that artificial stimulation can result in perceived colour in the absence of a coloured stimulus. This adds further to the evidence that colours are generated in the brain, that the brain does not passively chronicle the colours in the external world but actively constructs them. Isaac Newton saw this long ago when he wrote, “For the Rays, to speak properly, have no Colour. In them there is nothing else than a certain power and disposition to stir up a sensation of this Colour or that” – the power and disposition residing, I believe, within the V4 complex. Edwin Land also put it succinctly – “Colour is always a consequence, never a cause” – meaning that it is the consequence of some activity in the brain (though he did not specify where that activity might occur).

This highly interesting study gives powerful evidence in favour of these suppositions.

Romantic love and madness

Many, especially in the media, have commented about the work we published in 2000, showing the pattern of activity in the brain when those who are "madly and passionately" in love view a picture of the one they love. But there is another aspect of these results which is just as interesting, and which has received much less attention and comment. I refer to the fact that, under the same conditions, that is when a lover views the picture of the one he or she is passionately in love with, large parts of the brain, and particularly in the frontal lobes, become de-activated. The frontal lobes are of course those parts of the brain which have been traditionally associated with higher cognitive functions, including judgment. The clear implication is that judgment is more or less suspended, or at least much attenuated, when we are confronted with the one we love passionately.

In a sense, of course, this is a formal demonstration of what many have written about - the madness of love. We often ask someone who is passionately in love with a person whom we disapprove of: "Have you taken leave of your senses?" Well, in fact they have. And hence it is commonly, though not always, futile for disapproving parents and friends to try and prevent a liaison. The pattern of activation in their brain renders them less judgmental of the person they love than of others. The qualification is critical, for judgment is not suspended; it is only judgment about a particular individual that is suspended, implying a very selective brain procedure where judgment is concerned.

Here then is a possible neural basis for the "madness" of love that poets and writers since the time of Plato have written about. Nietzsche once wrote: "There is always some madness in love. But there is always some reason in madness". Perhaps the "reason" is to be sought in the pattern of neural de-activation that we have observed.

Of course, this pattern of activation is the one observed in the early and passionate stages of romantic love, a stage that usually does not continue indefinitely. One presumes that when a relationship becomes stabilized, or indifferent or even hostile, then the de-activation that is so prominent a feature of the passionate phase of love is no longer evident. It would be interesting to pursue such a study. It is now clear that there are chemicals, among them nerve growth factor, whose concentration rises during the early and passionate phase of romantic love, only to drop to normal levels once the relationship is stabilized or ended.

Nor is this suspension of judgment unique to romantic love. In a further study of the brain's love system, we studied the neural correlates of maternal love. The pattern of de-activation was remarkably similar to the one observed in romantic love, again leading one to believe that this constitutes the neural basis of the suspension of judgment - after all, mothers tend to be far less judgmental about their own children than about other children.

These are small steps in learning about the neural basis of love. There are other interesting discoveries to which I will return later.