“Why study connectomes if genomics is already so powerful?” Sebastian Seung asks in the introduction to Connectome. “The answer is simple: genes alone cannot explain how your brain got to be the way it is. As you lay nestled in your mother’s womb, you already possessed your genome but not yet the memory of your first kiss.”
Seung, a professor of neuroscience at MIT, believes that connectonomics, the study of neuronal circuitry, is about to revolutionise brain science. While genetics provides the initial blueprint, our connectome — a map of the connections between every neuron in our brain — also captures the ways in which we are moulded by experiences, such as learning, socialising, aging and disease. Seung goes as far as to argue that a person’s unique identity could be entirely defined by the connections between our brain cells.
There are significant technical hurdles to be overcome before a Human Connectome Project could get off the ground. First, the average adult brain houses something like 100 billion neurons, with a million billion synaptic connections between them. Today’s supercomputers could just about handle this volume of data, but we don’t yet have ways of making sense of it.
Second, current brain imaging methods that can be used on the living brain have spatial resolutions far below that of the individual neuron level, while methods that can be used on a preserved brain would take many years to gather the data. Nonetheless, setting these challenges against the dramatic progress that has been made in brain imaging and in IT, Seung makes a convincing case that by the end of the century mapping the human connectome will be within our grasp.
To put his theory in context, Seung takes us through the basics of brain anatomy and the history of neuroscience, and his clear prose and occasional wit make Connectome a surprisingly easy read. Much of this ground has been covered before, but those who are new to the subject will enjoy Seung’s telling of classic case studies. We are also reminded that scientists don’t shy away from a challenge. Despite limited technological means, the connectome of a one-millimetre-long worm, C.elegans, was mapped slice by slice in the 1970s and 1980s, a painstaking undertaking that took more than a decade to complete.
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After taking us through the science bit, Seung treats the reader to a final section of wildly speculative “what ifs”. Will we be able to upload our grandmother’s brain and read her memories? Will connectonomics allow us to bring cryonic brains back to life? Would a computer simulation of our brain be conscious and how would we know if it were?
The only criticism of this book is that, at times, it oversells the likely potential of connectonomics. We already know that not all neurons are equivalent and that the connections between them vary in strength, meaning that even if we successfully mapped the brain’s million billion connections, our circuit diagram would still be incomplete. We also know that the brain’s glial cells, once thought of as merely a supporting glue between neurons, play an important role in brain function, yet Seung completely ignores this area. On a more commonsense level, it is obvious that we are more than just our connectome. Our brain is also influenced by the cocktail of chemicals surrounding the neurons — add alcohol and we become a drunker version of ourselves.
Abstracting and simplifying the workings of the brain remains one of science’s most formidable challenges, and Connectome makes a convincing case that this emerging field will provide exciting new insights into how the brain works and the nature of personal identity.
Hannah Devlin is science editor of The Times
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Connectome: How the Brain’s Wiring Makes Us Who We Are, By Sebastian Seung, Published on June 7 by Allen Lane, £20
Read All About It
Erica Wagner gets out of her comfort zone to recommend a DVD, and finds that books about brains can blow your mind
Only once in my life have I ever bought a book on the strength of the title alone. It was 1985; I had wandered into Barnes & Noble on Broadway, and there it was on a table: The Man Who Mistook His Wife For A Hat.
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And so, with Oliver Sacks’ seminal tome the idea of popular neuroscience entered the wiring of my own brain and the brains of so many others. We have never looked back, and now the choice of reading matter in this vein is wide indeed.
And yet it’s a genre not wholly new. The idea that we are what our brains make us is brilliantly explored in Frigyes Karinthy’s memoir A Journey Round My Skull, first published in his native Hungary in 1937. Karinthy was a successful writer in Budapest, when one day, sitting in a café, he was disturbed by what sounded like the roaring of a passing train. It was, in fact, an auditory hallucination produced by a brain tumour; A Journey recounts its effect on his life. This is a neglected classic worth seeking out.
Brain injury doesn’t only affect the injured, of course, as Abigail Thomas’s moving memoir A Three Dog Life recounts. Thomas met her husband, Rich, through a small ad in The New York Review of Books; they had been blissfully married for only a few years when he was knocked down by a car outside their apartment building, suffering severe brain damage, and both their lives changed for ever. This is a book of boundless intelligence, entirely lacking in self-pity. Thomas is an inspiration.
Finally, while I know this column is called Read All About It, I’ll advise you to watch a film, too. The English Surgeon is a multi-award-winning documentary made by Geoffrey Smith in 2007 about the neurosurgeon Henry Marsh. Most of the time Marsh works in a London hospital, but the film documents his regular travels to a hospital in Kyiv, in the Ukraine, to give his time and skills to patients much less privileged than those he sees in the West. As with the Sacks, I came across this by chance, flicking through the channels late one night: go one better, and order the DVD theenglishsurgeon.com