How to map the 100 billion neurons in the brain

MIT neuroscientist Sebastian Seung believes mapping of of the human brain’s 100 billion neurons can be done — one cubic millimeter of brain tissue at a time.
Even more than our genome, our connectome shapes who we are, says Seung, who outlines his vision for connectome research in a new book, Connectome. “Clearly genes are very important, but because they don’t change after the moment of conception, they can’t really account for the effects of experience,” he says.
A streambed of consciousness
Seung envisions the brain’s connections as the “streambed” through which our consciousness flows. At a molecular level, that streambed consists of billions of synapses, in which one neuron sends signals to the next via chemical neurotransmitters. While scientists once believed that synapses could not be changed after formation, they now know that synapses are continuously strengthening, weakening, disappearing and reforming, as we learn new things and have new experiences.
At the Max Planck Institute for Medical Research in Heidelberg, Germany, neuroscientists in the laboratory of Winfried Denk have taken extremely thin slices of brain tissue and generated electron-microscope images of all the neural connections within each slice.