The Connectome: A New Way To Think About What Makes You You

connectome.jpg The nature vs. nurture debate pitted the hard and social sciences against each other for decades, if not centuries, stirred by a central concern with consciousness, what it means to be human, what makes a person, and, perhaps most interestingly to us egocentric beings, what constitutes character and personality. In Connectome: How the Brain's Wiring Makes Us Who We Are, Massachusetts Institute of Technology Professor of Computational Neuroscience Sebastian Seung proposes a new model for understanding the totality of selfhood, one based on the emerging science of connectomics -- a kind of neuroscience of the future that seeks to map and understand the brain much like genomics has mapped the genome.

A "connectome" denotes the sum total of connections between the neurons in a nervous system and, like "genome," implies completeness. It's a complex fingerprint of identity, revealing the differences between brains and, inversely, the specificity of our own uniqueness. Seung proposes a simple theory: We are different because our connectomes differ from one another. With that lens, he argues, any kind of personality change -- from educating yourself to developing better habits -- is a matter of rewiring your connectome.

That capacity is precisely what makes the connectome intriguing and infinitely promising -- unlike the genome, which is fixed from the moment of conception, the connetome changes throughout life. Seung explains:

Neuroscientists have already identified the basic kinds of change. Neurons adjust, or "reweight," their connections by strengthening or weakening them. Neurons reconnect by creating and eliminating synapses, and they rewire by growing and retracting branches. Finally, entirely new neurons are created and existing ones eliminated through regeneration.

We don't know exactly how life events -- your parents' divorce, your fabulous year abroad -- change your connectome. But there is good evidence that all four R's -- reweighting, reconnection, rewiring, and regeneration -- are affected by your experiences. At the same time, the four R's are also guided by genes. Minds are indeed influenced by genes, especially when the brain is 'wiring' itself up during infancy and childhood.* ...

The connectome theory of mental differences is compatible with the genetic theory, but it is far richer and more complex because it includes the effects of living in the world. The connectome theory is also less deterministic. There is reason to believe that we shape our own connectomes by the actions we take, even by the things we think. Brain wiring may make us who we are, but we play an important role in wiring up our brains.

Harnessing the power of those four R's, Seung believes, is the most important goal of neuroscience -- but, given your connectome is 100 billion times larger than your genome and has a million times more connections than your genome has letters, it's a daunting task. Still, new technologies and new directions of scientific curiosity are bringing us closer to understanding this microcosm of meticulously structured chaos.

Map of the C. elegans nervous system, or 'connectome,' borrowing from the language of genomics. DNA is a long chain-like molecule composed of nucleotides connoted by the letters A, C, G, and T, and your genome is the entire sequence of nucleotides in your DNA. Similarly, your connectome is the totality of connections between the neurons in your nervous system.

Presented by

Maria Popova is the editor of Brain Pickings. She writes for Wired UK and GOOD, and is an MIT Futures of Entertainment Fellow.

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