CONNECTOME

The key to understanding how brains work, writes Seung (Computational Neuroscience/MIT), is in the wiring.

The author champions the study of “connectomes,” the unique wiring diagrams of individual brains. However, we are barely at the connectome threshold. Indeed, if nothing else, Seung’s text is a convincing sales pitch for more funding. The goal would be to map all the synapses that all the neurons in the brain make with other neurons near or far. With such data we should be able to trace what memories look like; we could see how inputs from lower-order neurons feed into a single neuron that enables you to, say, recognize a celebrity. Comparing connectomes from normal vs. disordered brains might reveal faulty wiring that could explain schizophrenia or autism. These and other long-sought explanations of mental faculties are what “connectomics” promises. Moreover, we could see how experience changes the brain, through the “four R’s—reweighting, reconnection, rewiring, and regeneration.” Seung ably reviews the history of brain mapping, from the 19th-century phrenologists to the pioneers who associated regional brain damage with the loss of specific functions. There are newer technologies in electron and light microscopy that can slice the brain and capture serial neuronal images, and scientists are at work mapping the brains of roundworms and mice. But even if technology comes to the rescue, would it suffice? Seung ignores the role of the abundant glial cells, once thought of as supporting cells but which interact and affect neuronal behavior. The author’s final chapters on those seeking immortality by postmortem brain freezing or uploading their brains to a computer seem like sci-fi padding to the text.

Expect to hear more about connectomics as the field develops. Meanwhile, enjoy Seung’s book as a solid primer on brain physiology and the history of brain mapping.