In a initiative being compared to the Human Genome Project, neuroscientists are attempting to map all the major circuits in the human brain.
The five-year, $30-million Human Connectome Project will use custom-built brain scanners, a supercomputer and new brain analysis techniques to trace the anatomical 'wires' that interconnect thousands of different regions of the human brain.
"This effort will have a major impact on our understanding of the healthy adult human brain," says lead investigator David Van Essen of Washington University. "It will also enable future projects that probe what changes in brain circuits underlie a broad variety of disorders, such as autism and schizophrenia."
Brain scans of volunteers will be carried out at Washington University, the University of Minnesota and Saint Louis University, and new methods for analyzing the extremely complex datasets that arise from this will be developed.
Each human brain contains approximately 90 billion neurons, transmitting information across about 150 trillion synapses. "These cells and synapses form the circuits that underlie all our thinking and emotion – everything that makes each of us a unique individual," Van Essen says.
The project will map voxels, small patches of brain tissue, one to two millimeters on a side, that each contain as many as one million neurons. Bundles of long nerve cell branches from each voxel extend in complex trajectories, connecting cells in one voxel to those in others.
"At its essence, the human connectome is a description of the full pattern of connections between each brain region and every other brain region," says Van Essen.
Much of the project will focus on the cerebral cortex, where the most complex mental functions are carried out. As the structure and shape of individuals' brains vary significantly, the team plans to recruit and study 1,200 twins and siblings of twins.
"This lets us look at the heritability of different brain circuits by comparing identical twins to non-identical twins and siblings," he says. "It will also let us start linking various genes to specific aspects of brain circuitry."
Scanning techniques will include diffusion imaging, a new form of magnetic resonance imaging that produces detailed information on cell structure; resting state and task-related functional MRI; and magnetoencephalography, which can monitor very rapid patterns of activity involving millions of brain cells.
The information will allow scientists to map the brain's connections, track how they transmit information and identify how brain regions work together in dozens of networks and sub-networks.
The team says the data will be made available to other neuroscientists as quickly as possible.
"We're already working to create a well-organized data platform and tools that will allow scientists to drill down into the massive amounts of data the connectome project will produce and to efficiently extract the information they need to make exciting discoveries," he says.