The article, which will be available at http://www.pnas.org/cgi/doi/10.1073/pnas.0701519104, includes a link to a movie that visualizes what spontaneous fluctuations in the monkey's brain would look like. Coauthors of the article are Rolf Kötter, a neuroanatomist at Radboud University in Nijmegen in the Netherlands, and Michael Breakspear, a cognitive neuroscientist at the University of New South Wales in Australia.
When a person reads a book or talks with a friend, task-related neural activity occurs in different regions of the brain, but this activity only accounts for around 2 to 5 percent of the total activity of the brain. Fluctuations of similar magnitude -- the ones studied by Sporns and Honey -- occur when a person is at rest, doing nothing.
The nature of these "resting state fluctuations" is an active topic of research in cognitive neuroscience, with their mysterious origin prompting one prominent researcher to label them the "brain's dark energy," Sporns said. As yet, no one knows why these fluctuations occur or what their function might be.
Sporns and Honey suggest that a closer look at brain structure might provide a new perspective.
Despite the huge amount of work being done by neuroscientists, relatively little is known about how the human brain is structured -- how, for example the hundreds (the number is unknown) of regions in the human brain are connected. The computer model created by Sporns and Honey suggests that this very pattern of connectivity is crucial to generating and shaping brain activity in the resting and active brain.
Empirical work on the human brain is challenging due to the fact that the brain's intricacies cannot simply be manipulated and