Who do you think you are? A survey of the brain l December 23rd 2006 Republication, copying or redistribution by any means is expressly prohibited without the prior written permission of The Economist The Economist December 23rd 2006 A survey of the brain 1 Who do you think you are? Also in this section Captain Kirk’s revenge Emotion is essential to human survival. Page 2 Brainbox A history and geography of the brain. Page 3 Dreamweavers The perfect memory is of everything and nothing. Page 5 As others see us Dealing with people changes our minds. Page 7 I think, therefore I am, I think Consciousness awaits its Einstein. Page 9 Modern neuroscience, says Georey Carr, is groping towards the answer to the oldest question of all: who am I? N SEPTEMBER 13th 1848 a navvy servation moves the question who am I? Ocalled Phineas Gage was helping to from the realm of philosophy into the build a railway in Vermont. As gang fore- realm of science. man, he had the job of setting explosive Thirteen years after the incident in Cav- charges to blast a path through the hills endish, a French neurologist called Paul near a town called Cavendish. While he Broca systematised the study of how brain was tamping down one of the charges damage aects the mind with the discov- with an iron bar, it went o prematurely, ery that certain sorts of speech defect are driving the bar clean through his head. the result of damage to part of the brain Accidents on construction projects called the left temporal lobe (see overleaf happen all the time. The reason that peo- for a refresher course on brain anatomy ple remember Gage’s is that he survived it. and function). Local brain damage of this Or, rather, his body survived it. For the sort is known to neurologists as a lesion. Gage that returned to work was not the Studying it therefore became known as the Gage who had stuck the tamping rod into lesion method. that explosive-lled hole. Before, he had Broca’s new method was taken up been a sober, industrious individual, well quickly. All sorts of strange neurological respected and destined for success. After- symptoms are now explained by specic wards, he was a foul-mouthed drunkard, a brain damage. For example, an inability to drifter and a failure. His identity had been perceive movement (even though the changed in a specic way by specic dam- individual can see stationary objects) re- age to a specic part of his brain. sults from damage to part of the temporal Gage’s accident was intriguing because lobe, and an inability to recognise faces is it cast light on the question of dualism. caused by damage to the fusiform gyrus. This is the idea that although the mind No one now questions the idea that par- the selfinhabits the brain, it nevertheless ticular parts of the brain specialise in par- has an existence of its own and thus ticular activities. should not be equated with the brain. The Broca’s revolution, though, is incom- sudden change Gage underwent sug- plete. On the face of things, its discoveries A list of acknowledgments and sources can gested that brain and mind are not inde- might have meant the end of dualism, but be found at pendent. If the essence of individuality the world was not quite ready to embrace www.economist.com/surveys can be changed by a physical accident, it the mechanical explanation of self that implies that the brain is a mechanism the work of Broca and his successors im- An audio interview with the author is at which generates the self, rather than plied. For much of the 20th century, a wa- www.economist.com/audio merely an organ which houses it. This ob- tered-down version of dualism based on1 2 A survey of the brain The Economist December 23rd 2006 2 the idea of the psyche prevailed. The dis- In science, time tells. The good studies are tinction that psychiatry drew between repeated and make the textbooks. The bad neurological and psychiatric illness im- ones cannot be replicated and vanish plied that there was a psyche (whisper not down the memory hole. the word soul) that could somehow go Modern neuroscience has taken many wrong independently of physical symp- directions, and this survey will not at- toms in the brain. tempt to look at all of them. Instead, it will When that idea was challenged by the concentrate on four areas that may shed eectiveness of physical drugs, such as light on individual identity: the study of antidepressants, in treating psychiatric ill- the emotions; the nature of memory; the ness, dualism returned in a dierent guise. ways that brains interact with each other; Many people, most of whom would not and the vexed question of what, exactly, regard themselves as dualists, think of the consciouness is. brain as being like a computer, and the Such science is very much work in pro- mind as being like a piece of software that gress. Indeed, it is science of a type that runs on that computer. But this analogy, you need to do is put someone inside an would have been familiar to Broca and his too, is awed. You do not have to do much fMRI machine, give them a task to do and contemporaries, for in many cases the re- damage to a computer to stop it being able see which bits of the brain light up. searchers have only the haziest idea of to run programs. Yet as the case of Gage Naturally, the revolution in neurosci- where they are going. In the 19th century, and numerous subsequent individuals ence brought about by this new technol- when scientists were feeling their way to- has shown, the self can plod on, albeit ogy has its critics. They point out that big wards big concepts such as the laws of changed, after quite radical brain damage. conclusions are often drawn from small thermodynamics, electromagnetics and samples, that the changes in activity ob- the periodic table without really knowing The self in action served by fMRI are indirect (the technique what they were looking for, that was nor- Broca’s heirs, though, now have a range of measures blood ow and oxygen con- mal. These days there seem to be fewer new techniques with which to investigate sumption rather than the electrical activity new big concepts around, and experi- the question. The best-known is a way of of nerve cells) and that the resolution is ments are often conducted in the expec- scanning the brain called functional mag- poor (individual points in an fMRI picture tion of particular results. But neuroscience netic-resonance imaging (fMRI). What represent two or three cubic millimetres of is one area where big concepts certainly re- makes it so powerful is that it records activ- brain tissue, which means hundreds of main to be discovered. And when they are, ity as well as anatomy. It can, if you like to thousands of nerve cells). All these criti- they are likely to upend humanity’s under- put it that way, see the self in action. All cisms are justied. But these are early days. standing of itself. 7 Captain Kirk’s revenge Emotion is essential to human survival NE neuroscientist who could not be That people like Dr Wager can now lingers to this day. Oaccused of dealing in small samples is study emotion scientically shows how Two people in particular came to the Tor Wager, of Columbia University in New far things have come. For much of the 20th rescue: Paul Ekman and Joseph LeDoux. York. Dr Wager studies emotionsor, century, psychology sought to purge itself From the 1970s onwards, Dr Ekman, a psy- rather, he studies other people’s studies of of the sin of anthropomorphismthat is, chologist at the University of California, emotion. He has gathered together every inappropriately ascribing human motives San Francisco, challenged the anthropolo- fMRI study of emotion that he can lay his and feelings to other species. The tradition gists. He was responsible for the general hands ona total of some 150and per- known as behaviourism approached ani- agreement on the six basic emotions. He formed what statisticians call a meta-anal- mals as black boxes. Behaviourists stim- showed that the facial expressions associ- ysis. The result, illustrated overleaf, is as ulated them in dierent ways and re- ated with these emotions are universal, close as anyone has yet come to producing corded what happened. They did not ask and therefore almost certainly plumbed in an emotional map of the brain. what the animals felt. That both stymied genetically. The experience of emotion is one of the comparative studies of emotion and put In the 1980s Dr LeDoux, who is at New most fundamental parts of an individual’s out of the scientic arena the question of York University, challenged the behaviou- identity. Most neuroscientists now recog- how emotion evolved. Meanwhile an- rists. Instead of rejecting anthropomor- nise six basic emotions: anger, disgust, thropology, in a parallel ideological t phism, he embraced itthough he did so fear, joy, sadness and surprise. Dr Wager’s caused by the abuses of the eugenics carefully, noting the crucial importance of map is a neat illustration of how fMRI can movement, sought to expunge the idea the word inappropriately in the ascrip- be used to see the links between dierent that human behaviour had much in the tion of human feelings to animals. He parts of the brain that are involved in a sin- way of a genetic underpinning.