My Year Off by Robert McCrum Read Free Book Online

adaptable) in its functions than was once thought. The Victorian images of the brain that we’ve inherited were derived from railway systems, or the telephone switchboard, and suggested a rigid framework. Nowadays, the emphasis is on the adaptability of the brain to meet particular needs. Damage in one area will result, neurologists believe, in compensatory activity elsewhere. According to one Nobel prizewinning neuroscientist, Gerald Maurice Edelman, ‘The brain is a selective system, more like evolution than computation.’ Despite the extraordinary efforts now being devoted to neurological investigation, as the medical historian Roy Porter puts it, ‘Neurological conditions remain amongst the most intractable.’ Which brings us back to the brain’s place in our bodies.
    A great deal of the body’s energy is devoted to the brain (and vice versa). Most of that energy comes from the breaking down of glucose into carbon dioxide and water, a biochemical process that requires a high level of oxygen. Unlike the body’s muscles, the brain is unable to store glucose in reserve; it depends instead on a constant supply from arterial blood, and the same is true of the necessary oxygen. When the brain is deprived by a stroke of oxygen or glucose, it begins to suffocate almost immediately. Irreversible brain damage will occur within fifteen to thirty minutes of the initial deprivation, unless blood flow resumes.
    The brain is the miracle of the human frame, and aptly its biggest mystery. In recent years, neurological inquiry has become, with the study of genetics, the leading edge of medical research. The use of radioactive or fluorescent tracers and newly developed techniques of micro-electrode neurophysiology have brought the study of the brain centre-stage in the theatre of medicine. For the first time, researchers like Ray Dolan are making new discoveries about the organization of language and memory, and the way in which emotions interact with cognition, and how cognitive functions are composed of innumerable sub-processes.
    When I asked Dolan how easy it would be to replace the brain with a computer, he replied: ‘You would need an awful lot of chips. There are twenty billion neurons in the brain and each of those neurons makes on average ten thousand connections.’ He went on to describe ‘the extraordinary computational power of the living brain to represent so much, to be able to remember so much and its almost limitless memory capacity’. To put it another way, if you were somehow able to link up all the laptop computers of a city like London, you would beonly just beginning to equal the capacity of one ordinary brain.
    I also met with Dolan’s vivacious colleague at the Institute, Richard Frackowiak, who crisply described the brain as ‘an organ in a box with a hole at the bottom where the brain stem is situated’. A cerebral haemorrhage, he said, ‘squashes the brain. The pressure rises because the skull is absolutely rigid. In the worst possible case, the brain is actually squeezed out — that’s called “coning”. The pressure pushes it down through the hole at the bottom. But that is exremely rare and happens only in the more severe kind of stroke. You can get everything from fifteen minutes’ paralysis of the hand to a profound coma, from triviality to something fatal.’ Most people, in fact, die from other complications, notably cardio-respiratory difficulties. So how, I asked him, does a stroke kill you?
    ‘Well,’ Frackowiak replied, ‘it squashes the parts of the brain that deal with your heart rate and your breathing. It’s the same as being hanged, really. You die because your heart stops and you stop breathing.’ He went on, ‘There are many other ways you can die with a stroke. Lying in bed, you can get a raging pneumonia and die simply because your lungs fill up with fluid and you can’t breathe, can’t get oxygen in. And then there are many potential medical complications that can