It doesn’t take a neurosurgeon to know that the human brain is an incredibly complex place. Deciphering its secrets has been one of the most enticing yet elusive challenges of our time, and for centuries, scientists have attempted to understand the brain by both dividing it into specific regions (remember phrenology?) and by studying individual neurons under microscopes. The problem with these approaches is that these practices are either too rough or too limited in their scope. We need a way to understand the brain as a network of neurons in the same way that we understand computers and their networks of circuits.
Enter the world of the connectome. As MIT nueroscientist Sebastian Seung explains in his new book CONNECTOME: How the Brain’s Wiring Makes Us Who We Are, the connectome is “the totality of connections between the neurons in a nervous system.” One could even go so far as to say that “you are your connectome.” Seung proposes that if scientists could find a way to map the entire human connectome, we would finally have complete insight into understanding – and manipulating – the entire brain.
Imagine a world where any psychological issue can be treated by looking into the brain and manipulating connections between brain cells. Bad habits and psychopathies could be corrected by using just the right combinations of drugs, enzymes, lights, sounds, suggestions, and other experiences that are customized to an individual’s particular brain wiring. Complex skills like foreign languages and math could be learned faster by tweaking the brain itself. And in a super-distant future, Seung postulates, people might even be able to achieve the science-fiction dream of immortality by “uploading” our entire connectome – and hence our consciousness – into a virtual heaven, where we can “live” forever independently of our bodies.
Of course, these fantasies are dependent on a lot more advancement in both science and technology. The only animal connectome to have been fully mapped so far has been the 300-neuron connectome of the C. elegans roundworm, and that took scientists over seven years. The human connectome, in contrast, contains at least 100 billion neurons. No existing supercomputer comes even close to being able to process the mind-boggling number of connections between so many brain cells.
This is not to mention the fact that most connectome-mapping techniques require neuronal analysis under a microscope (i.e. a dead brain), which is not really useful if you want to map your own living connectome. Modern neuroscientists have so far only been able to identify the function of a single living neuron – affectionately known as the “Jennifer Aniston Neuron,” thanks to the image that was reliably conjured in the human subject’s mind each time the researchers stimulated that neuron. We still have an unbelievably long way to go before an individual’s entire connectome can be effectively mapped.
But according to Seung, “worthwhile things that have never been done can only be done by means that have never yet existed.” A worthy beginning of this massive effort is the 30 million Human Connectome Project, which was announced in 2010 by the U.S. National Institutes of Health (NIH). Yet even this huge project is still really only about “regional” connectomes (i.e. general fiber pathways through the brain), not individual neuronal connectomes. “To find [neuronal] connectomes,” Seung claims, “we will have to create machines that produce clear images of neurons and synapses over a large field of view.”
Seung still imagines that the human neuronal connectome could be completed by the end of this century, thanks to rapid advances in technology for imaging the brain and slicing brain tissue, and high-speed computers to crunch the data. Once all 100 billion neurons in the human brain are named, given a characteristic location & shape, and diagrammed, there’s no telling what future technologists will be able to do with these connectome maps. (Writing “apps” for the human brain, anyone?) CONNECTOME is a significant book in that it is helping to motivate a future generation of connectome researchers, by making the concept feel so accessible to both the layperson and the professional brain geek alike.