January 14, 2011 6:33 pm

Mind games

 
A group of men yawning

‘Mirror’ neurons mimic observed behaviour, which might be why we yawn when others do

The Tell-Tale Brain: Unlocking the Mystery of Human Nature, by VS Ramachandran, Heinemann, RRP£20, 382 pages

The Mind’s Eye, by Oliver Sacks, Picador, RRP£17.99, 272 pages

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IN Essay

Self Comes to Mind: Constructing the Conscious Brain, by Antonio Damasio, Heinemann, RRP£25, 378 pages

The greatest mysteries of science lie within the fields of neuroscience and cosmology. How does the brain produce consciousness? How did our universe start and how will it end? The immensity of the intellectual challenge – and the public interest in possible answers – inspires leading practitioners to communicate their ideas through books, in a way that is matched in few other fields of science.

A trio of top neuroscientists – VS Ramachandran, Antonio Damasio and Oliver Sacks – have recently published books that convey the excitement of current brain research. Ramachandran has the broadest sweep of the three authors: The Tell-Tale Brain explains how and why the human brain makes us “truly unique and special, not ‘just’ another species of ape”. Damasio is somewhat more limited in scope but even more ambitious in intent: his book Self Comes to Mind attempts to describe the neural processes that give rise to consciousness. And in The Mind’s Eye, Sacks views the workings of the brain through the prism of vision.

Although each author has his own distinctive approach, there are many common threads. One is the huge amount that has been learned by studying people with brain abnormalities, whether caused by inheritance, illness or accident.

Sacks made his name with The Man Who Mistook His Wife for a Hat, published in 1985. The approach he took – showing what neuroscientists can learn from the way an individual patient’s symptoms relate to specific damage in his or her brain – has served his readers well over the course of several subsequent books.

While The Mind’s Eye follows the same formula, based on sympathetic treatment of case studies, it has even more power this time because Sacks himself features as a patient towards the end of the book. His personal diary, analysing the effects on his vision of a tumour behind his right eye, is the most moving account he has ever published. Intense fear of going blind is mixed with fascination about the tumour’s impact on his optic nerves and the way his brain processes their signals.

 

Ramachandran, too, makes excellent use of case histories. He learns much more from working with patients than from subjecting healthy volunteers to laboratory experiments. Indeed, intensive study of patients – and the astonishing way some people can adapt to or even overcome severe neurological damage – has led to one of the biggest shifts in neuroscience over the past 20 years: recognition of the brain’s “plasticity”.

Until the 1990s, the brain was seen as consisting of many specialised modules, interacting in an exceedingly complex way but essentially hard-wired genetically to perform specific tasks. Now a very dynamic picture is emerging, with far more interaction between the brain areas than previously suspected.

A change in one module – from disease or injury, or learning and life experience – can lead to big changes in many other modules to which it is connected. In some circumstances, one can even take over the functions of another. At the same time brand new neurons (brain cells) can form in parts of the adult brain, in contravention of the 20th-century orthodoxy that we only lose neurons as we age.

All this is, of course, potential good news for damaged brains. Sacks’s patients make heroic efforts to overcome the effects of stroke, which wipes out certain neural clusters, by bringing others into play. For example, Howard Engel, a Canadian novelist, gradually retrained his brain to read again after suffering sudden alexia – the inability to distinguish written letters or words – and he managed to resume his writing career.

Sacks draws attention to the “increasing evidence for the extraordinarily rich interconnectedness and interactions of the sensory areas of the brain, and the difficulty therefore of saying that anything is purely visual or purely auditory or purely anything”.

The world of the blind is particularly rich in such in-between sensory states for which we have no common language. Blind people learn to find their way around without sight to an astonishing extent. This sensory infrastructure enables blind people who receive a retinal implant to interpret its electronic signals as mental pictures, even though the current first-generation devices are extremely simple compared with a real retina.

 

A different manifestation of the inter-mingling of the brain’s circuits is synaesthesia – the strange blending of the senses that some people experience as a result of their unusual brain wiring. Ramachandran has made a particular study of synaesthetes, such as Mirabelle, who experiences a colour whenever she sees a number, even if it is written in black; or Esmeralda, who experiences a different colour for each musical note; or Francesca, who feels a vivid emotion when she closes her eyes and touches a particular texture: denim brings extreme sadness, wax embarrassment, silk calm, orange peel shock, sandpaper guilt.

Until recently, synaesthesia was seen as a very rare condition, bordering on mental illness, but Ramachandran shows that it is both more common and more constructive than neurologists had realised. He even believes it holds a clue to human creativity (it has been suggested that artists and writers such as Wassily Kandinsky, Jackson Pollock, Vladimir Nabokov and Arthur Rimbaud explored synaesthesia in their work). At the same time, the phenomenon opens the way to studying interactions between sensory perceptions and aspects of consciousness.

The authors – and Damasio in particular – emphasise the fact that the brain is part of the body and vice-versa. A map of the body is imprinted on the brain and, when this mental map does not match the sensory input from the real body, the ensuing disharmony disrupts the self’s sense of unity.

Phantom limbs are a simple example. If your arm is amputated, its image stays in your brain and can cause agony when there are no signals from a real arm. Ramachandran has pioneered the treatment of phantom limb pain by tricking the brain, through a clever arrangement of mirrors, into seeing movement in the missing arm, which is often enough to kick-start a neural change and solve the problem. For Damasio, the mental map of body, which resides in an ancient part of the brain called the upper brain stem, constitutes the proto-self – the foundation of the conscious mind.

The step up to the next level of consciousness and human awareness is made possible by a group of brain cells called mirror neurons, which are activated when you see someone else doing something. To give a simple example, they may explain why yawning is so contagious. Both Damasio and Ramachandran regard the discovery of mirror neurons, at the University of Parma, Italy, in the 1990s, as perhaps the most important development in fundamental neuroscience of the past two decades.

The Italian scientists identified mirror neurons in monkeys. When an animal saw a researcher move his hand, this activated neurons in the brain’s motor control region relating to hand movement, as if the monkey, rather than the researcher, was performing the action. But they play a much more important role in the human brain.

Damasio calls mirror neurons “the ultimate as-if body device”. They allow you to imitate the movements of others, setting the scene for the cultural inheritance of skills developed and honed by others. They may also have propelled a self-amplifying feedback loop that accelerated the evolution of the human brain, with sympathetic reactions to other people made possible by emotional mirror neurons. Ramachandran sees autism as the result of a dysfunctional mirror neuron system.

 

A key concept in Self Comes to Mind, which does not come up in the other two books, is homoeostasis – the drive within organisms to maintain the balance of all biological processes within a range that is safe and comfortable for life. Although the basic idea of homoeostasis dates back to the early 20th century, Damasio pushes it further and harder than any previous author has dared, arguing that improved homoeostatic control has driven the evolution of the brain and then the emergence of consciousness.

He moves beyond basic biological homeostasis to “sociocultural homoeostasis” – maintaining a balance in society and culture through justice, politics, economics, the arts and science. “The dramatic reduction of violence along with the increase in tolerance that has become so apparent in recent centuries would not have occurred without sociocultural homoeostasis,” Damasio writes.

Although there has not been time for much genetic evolution in the human brain since the emergence of Homo sapiens 200,000 years ago, and fully modern humans about 50,000 years ago, Damasio argues that independent-minded people with a “rebellious” spirit, who can question and argue about their place in the world, are an even more recent development. The invention of writing may have played a role here. His point is that social and cultural factors have changed the level of consciousness and awareness over a mere instant in evolutionary time.

Evolution also plays an important role in the other two books. Sacks points out that all writing systems, from Roman letters to Chinese ideograms, have evolved to take advantage of the preference of “inferotemporal neurons” in our brains for certain shapes found in the natural environment. While alphabets and ideograms from around the world may look superficially different, topological analysis shows a strong underlying similarity that would not be present if written shapes were an arbitrary cultural choice.

The origins of writing and reading depend on the plasticity of the brain and “experiential selection”, Sacks writes. “Natural selection, for Darwin, did not forbid cultural and individual developments on a timescale hundreds of thousands of times faster than evolutionary development. On the contrary, it prepared the ground for them.”

Ramachandran demonstrates how many uniquely human mental traits evolved through the novel deployment of brain structures that originally evolved for other reasons. “Evolution found ways to radically repurpose many functions of the ape brain to create entirely new functions,” he writes. “Some of them – language comes to mind – are so powerful that I would go so far as to argue they have produced a species that transcends apehood to the same degree by which life transcends mundane chemistry and physics.”

The three authors – all incidentally born and educated elsewhere in the world before moving to the US as ambitious young researchers – have produced books that will give pleasure to anyone interested in original thinking about the brain.

Sacks is the easiest to read but least ambitious. Damasio is the opposite extreme: often hard-going and technical but breathtakingly original. Ultimately, however, I did not feel convinced by his theory of human consciousness – though I was not confident that I had fully understood the argument of Self Comes to Mind. My favourite of the trio is The Tell-Tale Brain; I cannot imagine a better account of the sweep of contemporary neuroscience.

It is clear from all three books and several others published on neuroscience over the past year that while researchers are making good progress in uncovering the workings of the human brain – its biological circuitry, chemistry and anatomy – they are still far from understanding thoughts and emotions at any fundamental level. Even Damasio’s unproven theory represents no more than an outline of how consciousness might have evolved, rather than a real explanation of how we feel conscious.

Yet I believe the human brain will eventually understand itself. Whether it is capable even in principle of grasping the ultimate principles of cosmology – multiple dimensions, maybe even multiple universes – is more doubtful.

Clive Cookson is the FT’s science editor

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