A Review of Sebastian Seung’s The Connectome: How the Brain’s Wiring Makes Us Who We Are. Mariner Books, 2013.
There is no scientific field more exciting than contemporary neuroscience, poised as it is to develop concepts and technologies that will finally penetrate and manipulate fundamental mechanisms of the human mind. There is also no scientific field more arrogantly simplistic, bedazzled as it is by reductionist theory and fantasies of human power and control over complex biological processes. MIT neuoroscientist Sebastian Seung’s brilliant book manages to be both.
Seung is a rising rockstar scientist with drop-dead good looks, bold fashion sense (he typically sports jeans and t-shirt and showed up to a recent high profile debate wearing shiny gold sneakers), and a knack for making complicated ideas and profound problems in neuroscience not only understandable but cool. He gave a popular TED talk laying out the central thesis of his work that “I am my connectome,” that the sum total of synaptic connections within the brain constitute human selfhood in all its rich uniqueness. This book is a fuller elaboration of that idea and its intellectual history, and a fascinating account of the development of the theories and technologies that Sueng believes will make possible what he views as the ultimate goal of neuroscience – a complete map of the human connectome.
Pursuing this goal, according to Seung, will have both philosophical benefits in terms of understanding human nature and practical benefits in terms of getting at the true causes of mental disorders like autism and schizophrenia which he argues may usefully be thought of as “connectopathies”—abnormal patterns of neural connection. Beyond this, Seung argues that it is theoretically possible (or at least not yet a proven impossibility) that in the future connectomics will advance to the point of being able to fully read off and duplicate the contents of individual human consciousness thus essentially achieving the dream of immortality. Though Seung hedges on whether he really believes projects like cryonics and the uploading of consciousness are plausible or even desirable, he clearly embraces the broader transhumanist dream of developing technological means of human improvement. He concludes the book with grand vision that evokes the technological singularity, when humans will finally transcend the limits of their biology:
Connectomics marks a turning point in human history. As we evolved from apelike ancestors on the African savannah, what distinguished us was our larger brains. We have used our brains to fashion technologies that have given us ever more amazing capabilities. Eventually these technologies will become so powerful that we will use them to know ourselves—and to change ourselves for the better.”
Seung acknowledges that neuroscience is very far from achieving the extraordinarily difficult goal of mapping the connectome. It took scientists more than a decade to map the connectome of the nematode C. elegans, whose simple brain consists of only 300 neurons and 7000 synaptic connections. The human connectome is 100 billion times larger, with a million times more connections than the human genome has letters. But as Seung explains, the development of technologies that automate much of the work are beginning to make this enormous project feasible.
However the real problem is not just size, but complexity. While the nematode connectome is relatively fixed and stable from one individual organism to the next, the connectome of every human being is unique, reflecting the ongoing re-wiring of synaptic connections within the brain as each individual interacts with the environment. Yes, there is an underlying brain structure common to all human brains, but the wiring of the connectome evolves in a way that reflects the unique experience of the world each individual gains through their senses, their thoughts and feelings, and even the ideas they have encountered through participation in human culture. Connectionism itself suggests that human consciousness can never be reducible to a universal brain structure or state; it seems quite plausible that ostensibly identical synaptic connections could be encoded with different mental content.
In recognizing the dialectical relationship between brain and environment, connectionism would seem to avoid the crude reductionism of discredited intellectual ancestors like phrenology that sought to identify specific regions of the brain with complex personality traits and mental functions. Indeed, one of Seung’s clearest messages is that “the connectome is where nature meets nurture.” If that is true, then traditional understandings of the role of culture and society should be seen as equally important in the formation of self, and psycho-social approaches equally important as biotechnology in dealing with mental disorders. But Seung and other neuroscientist are not much interested in the dense matrix of “nurture” constituted by human culture and society. They are really interested only in the wiring.
For example, Sueng makes much of the infamous discovery of the Jennifer Aniston neuron – a specific neuron in themedial temporal lobe (MTL) that fires only when research subjects look at a photograph of her, along with neurons that fire exclusively on perception of other celebrities. He extrapolates from this to theorize about how perception works in general by comparing the brain to an army of paparazzi employed by a magazine that seeks to publish titillating photos of movie stars:
One hounds Jennifer Aniston with his camera, another devotes himself to Halle Berry, and so on. Every week, their activities determine which celebrities appear in the magazine, just as the spiking of MTL neurons determines which celebrities are perceived by the person.”
While this is a fascinating speculative theory about the mechanism of perception in the brain, it actually tells us very little about the mind. Following the actions of this “army of papparazi” might tell us how certain things end up in “the magazine” of the mind, but it really does not tell us why that magazine devotes attention to celebrities at all, who “buys” it, etc. Seung tries to meet this kind of objection by suggesting that the “Jen neuron” is activated by a population of neurons triggered by neurons devoted to components of the perception – neurons that fire for blonde hair, dazzling smiles, blue eyes, and other attributes. But this comes to seem very much like a return to phrenology. It’s as though Seung seeks to explain why you assembled songs into a playlist by examining the circuitry of your iPod. To explain your playlist, we are going to need to know some things about the society and culture you live in.
All of that said, Seung’s book is well worth reading for its clear discussion of what neuroscience is uncovering about the workings of the brain. Neuroscience is indeed opening an exciting frontier, and work toward mapping the brain may tell us some valuable things about human nature and mental illness. But as we think about these possibilities, and how to prioritize our investments in science, we should also acknowledge that there are things it will never be able to tell us.