After centuries searching for the seat of consciousness, scientists have identified a good place to look.
A "core" region of the brain has been identified by an international team which has produced the first complete high-resolution map of the human cerebral cortex, the wrinkly surface of the brain where awareness, thought and other features of high level thinking reside.
The team traced the connections between millions of brain cells and identified a highly connected single network core, or hub, that may be key to the workings of both hemispheres of the brain.
The work by the researchers from Indiana University, University of Lausanne, Switzerland, Ecole Polytechnique Fédérale de Lausanne, Switzerland, and Harvard Medical School marks a major step in understanding the most complicated and mysterious organ in the universe.
They believe the discovery will be an invaluable tool for interpreting brain scans and understanding the brain. As for consciousness, that quest will have to wait until neuroscientists can agree on a precise definition of what they are talking about.
The study not only provides a comprehensive map of brain connections (the brain "connectome"), but also describes a novel application of a non-invasive technique that can be used by other scientists to continue mapping the trillions of neural connections in the brain at even greater resolution, which is becoming a new field of science termed "connectomics."
The team hopes to use the information to build biologically realistic models in a computer which in turn will "help us understand processes that are difficult to observe, such as disease states and recovery processes to injuries," said Dr Olaf Sporns, co-author of the study in the journal PLoS Biology and a neuroscientist at Indiana University.
Until now, scientists have mostly used scanners to measure hotspots of brain activity - locating which parts of the brain use more blood during perception or cognition - but there has been little understanding of the role of the underlying anatomy in generating this activity.
In this new study, the Swiss team of neuroimaging researchers could trace out fibres that extend between brain cells by measuring how they interfered with the diffusion of water molecules through brain tissue.
The study applies this technique to the entire human cortex, resulting in maps of millions of neural fibres running throughout this highly furrowed part of the brain.
At Indiana University, Dr Sporns then carried out a computer analysis trying to identify regions of the brain that played a more central role in the connectivity, serving as hubs in the cortical network. Surprisingly, these analyses revealed a single highly and densely connected structural core in the brain of all participants.
"The core, the most central part of the brain, is in the medial posterior portion of the cortex, and it straddles both hemispheres," Sporns said.
"This wasn't known before. Researchers have been interested in this part of the brain for other reasons. For example, when you're at rest, this area uses up a lot of metabolic energy, but until now it hasn't been clear why."
Most important, in a study of five volunteers doing various tasks, they found that the connections of the brain did influence the overall activity. "This means that if we know how the brain is connected we can predict what the brain will do," said Dr Sporns.
Dr Sporns and Dr Patric Hagmann now plan to look at more brains to map brain connectivity as brains develop and age, and as they change in the course of disease and dysfunction.
Co-authors include Reto Meuli, University Hospital Centre and University of Lausanne; Leila Cammoun and Xavier Gigandet, Ecole Polytechnique Fédérale de Lausanne; Van Wedeen, Massachusetts General Hospital and Harvard Medical Centre; and Christopher Honey, Indiana University.
Thanks for your comments.